Journal articles: 'Metal Oxyhydroxides'

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Olatunde Popoola, Samuel, Xiqiu Han, Yejian Wang, Zhongyan Qiu, and Ying Ye. "Geochemical Investigations of Fe-Si-Mn Oxyhydroxides Deposits in Wocan Hydrothermal Field on the Slow-Spreading Carlsberg Ridge, Indian Ocean: Constraints on Their Types and Origin." Minerals 9, no. 1 (December 28, 2018): 19. http://dx.doi.org/10.3390/min9010019.

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We have studied morphology, mineralogy and geochemical characteristics of Fe-oxyhydroxide deposits from metal-enriched sediments of the active (Wocan-1) and inactive (Wocan-2) hydrothermal sites (Carlsberg Ridge, Northwest Indian Ocean). Fe-oxyhydroxide deposits on the Wocan-1 site are reddish-brownish, amorphous and subangular. They occur in association with sulfides (e.g., pyrite, chalcopyrite and sphalerite) and sulfate minerals (e.g., gypsum and barite). The geochemical composition shows enrichment in transition metals (Ʃ (Cu + Co + Zn + Ni) = ~1.19 wt. %) and low (<0.4 wt. %) values of Al/(Al + Fe + Mn) ratio. The Wocan-2 samples show poorly crystallized reddish brown and yellowish Fe-oxyhydroxide, with minor peaks of goethite and manganese oxide minerals. The mineral assemblage includes sulfide and sulfate phases. The geochemical compositions show two distinct types (type-1 and type-2). The type-1 Fe-oxyhydroxides are enriched in transition metals (up to ~1.23 wt. %), with low values of Fe/Ti vs. Al/(Al + Fe + Mn) ratio similar to the Wocan-1 Fe-oxyhydroxides. The type-2 Fe-oxyhydroxides are depleted in transition metals, with Al/(Al + Fe + Mn) ratio of 0.003–0.58 (mean value, 0.04). The ridge flank oxyhydroxides exhibit an extremely low (mean value ~ 0.01) Fe/Mn ratio and a depleted concentration of transition metals. Our results revealed that the Wocan-1 Fe-oxyhydroxides and type-1 Fe-oxyhydroxides of the Wocan-2 site are in the range of Fe-oxyhydroxides deposits that are precipitated by mass wasting and corrosion of pre-existing sulfides. The type-2 Fe-oxyhydroxides are precipitated from sulfide alteration by seawater in an oxygenated environment relative to type-1. The association of biogenic detritus with the oxyhydroxides of the ridge flanks and the low Fe/Mn ratio suggests hydrogenous/biogenic processes of formation and masked hydrothermal signatures with distance away from the Wocan hydrothermal field.

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Sipos, Péter, Viktória Kovács Kis, Réka Balázs, Adrienn Tóth, and Tibor Németh. "Effect of pedogenic iron-oxyhydroxide removal on the metal sorption by soil clay minerals." Journal of Soils and Sediments 21, no. 4 (February 19, 2021): 1785–99. http://dx.doi.org/10.1007/s11368-021-02899-x.

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Abstract Purpose The close association of Fe-oxyhydroxides and clay minerals might influence the sorption properties of these components. We aimed to study the effect of removing the pedogenic Fe-oxyhydroxides on the sorption of Cd, Cu, Pb, and Zn by the clay mineral particles in soils with contrasting pH. Methods Competitive batch sorption experiments before and after Fe-oxyhydroxide extraction in soils were carried out together with the direct analysis of the metal sorption on individual particles of ferrihydrite, smectite, and illite/smectite by TEM. Results Ferrihydrite was a more effective metal sorbent than clay minerals, although its removal resulted in decreased sorption only for Cd, Cu, and Zn. Ferrhydrite coating blocked metals’ access for certain sorption sites on clay surfaces, which were only accessible for Pb as the most efficient competitor after removing the coating. This observation was the most remarkable for the smectite particles in the alkaline soil. Mineral surfaces sorbed higher Cu than Pb concentrations and higher Zn than Cd concentrations despite the former metals’ lower bulk sorption. Thus, organic surfaces and precipitation contributed to Pb and Cd’s retention to a greater extent than for Cu and Zn. The structural Fe of smectite also promoted the metal sorption in both soils. Conclusion Removal of iron-oxyhydroxide coatings from the soil affects metal sorption selectively. Direct study of metal sorption on individual soil particles enables us to gain a more in-depth insight into soil minerals’ role in this process.

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Lim, Chee Shan, Chun Kiang Chua, Zdeněk Sofer, Kateřina Klímová, Christopher Boothroyd, and Martin Pumera. "Layered transition metal oxyhydroxides as tri-functional electrocatalysts." Journal of Materials Chemistry A 3, no. 22 (2015): 11920–29. http://dx.doi.org/10.1039/c5ta02063h.

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Pechenyuk, S. I., Yu P. Semushina, and L. F. Kuz’mich. "Adsorption affinity of anions on metal oxyhydroxides." Russian Journal of Physical Chemistry A 87, no. 3 (February 3, 2013): 490–96. http://dx.doi.org/10.1134/s0036024413030205.

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SPARK, K. M., B. B. JOHNSON, and J. D. WELLS. "Characterizing heavy-metal adsorption on oxides and oxyhydroxides." European Journal of Soil Science 46, no. 4 (December 1995): 621–31. http://dx.doi.org/10.1111/j.1365-2389.1995.tb01358.x.

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Tang, Cheng, Hao-Fan Wang, Han-Sen Wang, Fei Wei, and Qiang Zhang. "Guest–host modulation of multi-metallic (oxy)hydroxides for superb water oxidation." Journal of Materials Chemistry A 4, no. 9 (2016): 3210–16. http://dx.doi.org/10.1039/c6ta00328a.

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Barforoush, Joseph M., Dylan T. Jantz, Tess E. Seuferling, Kelly R. Song, Laura C. Cummings, and Kevin C. Leonard. "Microwave-assisted synthesis of a nanoamorphous (Ni0.8,Fe0.2) oxide oxygen-evolving electrocatalyst containing only “fast” sites." Journal of Materials Chemistry A 5, no. 23 (2017): 11661–70. http://dx.doi.org/10.1039/c7ta00151g.

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Shi, Zhikai, Zebin Yu, Ronghua Jiang, Jun Huang, Yanping Hou, Jianhua Chen, Yongqing Zhang, Hongxiang Zhu, Bing Wang, and Han Pang. "MOF-derived M-OOH with rich oxygen defects by in situ electro-oxidation reconstitution for a highly efficient oxygen evolution reaction." Journal of Materials Chemistry A 9, no. 18 (2021): 11415–26. http://dx.doi.org/10.1039/d1ta01638e.

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Metal-oxyhydroxides with rich oxygen defects (M-OOHv) derived from MOFs were prepared through an efficient, simple, and green in situ electro-oxidation reconstitution strategy for a highly efficient oxygen evolution reaction.

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Chen, Tse-Wei, Shen-Ming Chen, Ganesan Anushya, Ramanujam Kannan, Pitchaimani Veerakumar, Mohammed Mujahid Alam, Saranvignesh Alargarsamy, and Rasu Ramachandran. "Metal-Oxides- and Metal-Oxyhydroxides-Based Nanocomposites for Water Splitting: An Overview." Nanomaterials 13, no. 13 (July 5, 2023): 2012. http://dx.doi.org/10.3390/nano13132012.

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Water electrolysis is an important alternative technology for large-scale hydrogen production to facilitate the development of green energy technology. As such, many efforts have been devoted over the past three decades to producing novel electrocatalysis with strong electrochemical (EC) performance using inexpensive electrocatalysts. Transition metal oxyhydroxide (OxH)-based electrocatalysts have received substantial interest, and prominent results have been achieved for the hydrogen evolution reaction (HER) under alkaline conditions. Herein, the extensive research focusing on the discussion of OxH-based electrocatalysts is comprehensively highlighted. The general forms of the water-splitting mechanism are described to provide a profound understanding of the mechanism, and their scaling relation activities for OxH electrode materials are given. This paper summarizes the current developments on the EC performance of transition metal OxHs, rare metal OxHs, polymers, and MXene-supported OxH-based electrocatalysts. Additionally, an outline of the suggested HER, OER, and water-splitting processes on transition metal OxH-based electrocatalysts, their primary applications, existing problems, and their EC performance prospects are discussed. Furthermore, this review article discusses the production of energy sources from the proton and electron transfer processes. The highlighted electrocatalysts have received substantial interest to boost the synergetic electrochemical effects to improve the economy of the use of hydrogen, which is one of best ways to fulfill the global energy requirements and address environmental crises. This article also provides useful information regarding the development of OxH electrodes with a hierarchical nanostructure for the water-splitting reaction. Finally, the challenges with the reaction and perspectives for the future development of OxH are elaborated.

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Xu, Zhichuan J. "Transition metal oxides for water oxidation: All about oxyhydroxides?" Science China Materials 63, no. 1 (September 3, 2019): 3–7. http://dx.doi.org/10.1007/s40843-019-9588-5.

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Bogush, A. A., O. G. Galkova, and N. V. Ishuk. "Geochemical barriers to elemental migration in sulfide-rich tailings: three case studies from Western Siberia." Mineralogical Magazine 76, no. 7 (December 2012): 2693–707. http://dx.doi.org/10.1180/minmag.2012.076.7.05.

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AbstractThis study describes geochemical barriers that have developed at three different localities in sulfiderich tailings in the Kemerovo region of Western Siberia, Russia. Iron oxyhydroxides, gypsum, malachite, chalcanthite, goslarite, bianchite, gunningite and copper and zinc chlorides crystallized in the sequence specified at an evaporative barrier around glassy slag produced by the Belovo zinc processing plant. A complex cemented barrier that has developed within the old Salair sulfide tailings contains two well defined layers: an upper layer containing Fe(III) minerals and gypsum as cements in which Pb, As, Mo, Ni and Co have been deposited; and (2) a lower calcite- and gypsum-bearing layer, in which phases containing Zn, Cd and Cu have been deposited. A complex organic-mineral barrier below the Ursk sulfide tailings consists of peaty organic matter, clay minerals and iron oxyhydroxides cemented by gypsum. Elements that have leached from the tailings are present in this barrier in a variety of different forms: Ca and Mn are present as water-soluble species; Cu, Fe and Zn are present as species produced by interaction with organic matter via ion-exchange, metal humate formation and cation bridging in organic-mineral complexes; Pb and As are co-precipitated with and/or adsorbed onto iron oxyhydroxides; gold has been deposited as minute particles of native metal. The mechanisms for the formation of the different geochemical barriers are discussed.

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Hausmann, Jan Niklas, Stefan Mebs, Konstantin Laun, Ingo Zebger, Matthias Driess, and Prashanth W. Menezes. "Precatalyst Reconstruction during the Electrocatlytic Oxygen Evolution Reaction: The Influence of the Precursor and the Transformation Conditions." ECS Meeting Abstracts MA2022-02, no. 48 (October 9, 2022): 1829. http://dx.doi.org/10.1149/ma2022-02481829mtgabs.

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The oxygen evolution reaction (OER) is the most likely reaction to supply electrons and protons for future green fuel and chemical formation, and thus many materials have been studied for their suitability as OER (pre)catalysts. However, in-situ and post-catalytic studies have shown that the harsh OER conditions alter the electrode materials, causing a reconstruction to mainly transition metal oxyhydroxides in alkaline and near-neutral electrolyte. As this reconstructed phase is the real catalyst, its atomic structure and physical properties must be precisely known. These properties will be affected by the precatalyst and the reconstruction conditions, like the product of a chemical reaction is affected by the substrate and reaction conditions. For the elucidation of such reconstruction processes, a broad range of spectroscopic (in-situ) methods combined with new, meaningful precursors are required. Herein, investigations on the reconstruction of several precatalysts such as phosphites,1 borophosphates,2 selenites,3 silicides,4 and elemental metal foams are presented. These reconstructions were analysed by in situ Raman and X-ray absorption spectroscopy together with state-of-the-art post-mortem characterization techniques. In an effort to connect this data, we propose ideas relating the precatalyst structure with the one of the formed oxyhydroxides. Additionally, we critically debate the question: why should a non-oxyhydroxide phase be used for the OER if it will anyway reconstruct? Moreover, as mentioned, also the reconstruction conditions affect the specific nature of the formed oxyhydroxide. Considering this, we present a case, where from the same precatalyst, catalysts with entirely different structural and electrocatalytic properties were obtained by only changing the electrochemical reconstruction conditions (potential, pH, electrolyte composition...). References: Menezes, P. W. et al. A structurally versatile nickel phosphite acting as a robust bifunctional electrocatalyst for overall water splitting. Energy Environ. Sci. 11, 0–13 (2018). Menezes, P. W. et al. Helical cobalt borophosphates to master durable overall water-splitting. Energy Environ. Sci. 12, 988–999 (2019). Hausmann, J. N. et al. Understanding the formation of bulk- and surface-active layered (oxy)hydroxides for water oxidation starting from a cobalt selenite precursor. Energy Environ. Sci. 13, 3607–3619 (2020). Hausmann, J. N. et al. Evolving Highly Active Oxidic Iron(III) Phase from Corrosion of Intermetallic Iron Silicide to Master Efficient Electrocatalytic Water Oxidation and Selective Oxygenation of 5‐Hydroxymethylfurfural. Adv. Mater. 33, 2008823 (2021). Figure 1

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Myers, Dwight L., Nathan S. Jacobson, Charles W. Bauschlicher, and Elizabeth J. Opila. "Thermochemistry of volatile metal hydroxides and oxyhydroxides at elevated temperatures." Journal of Materials Research 34, no. 3 (January 30, 2019): 394–407. http://dx.doi.org/10.1557/jmr.2018.425.

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Burisch, Mathias, Max Frenzel, Henning Seibel, Albert Gruber, Marcus Oelze, Jörg A. Pfänder, Cynthia Sanchez-Garrido, and Jens Gutzmer. "Li-Co–Ni-Mn-(REE) veins of the Western Erzgebirge, Germany—a potential source of battery raw materials." Mineralium Deposita 56, no. 6 (June 25, 2021): 1223–38. http://dx.doi.org/10.1007/s00126-021-01061-4.

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AbstractSituated in the western Erzgebirge metallogenetic province (Vogtland, Germany), the Eichigt prospect is associated with several quartz-Mn-Fe-oxyhydroxide veins that are exposed at surface. Bulk-rock geochemical assays of vein material yield high concentrations of Li (0.6–4.1 kg/t), Co (0.6–14.7 kg/t), and Ni (0.2–2.8 kg/t), as well as significant quantities of Mn, Cu, and light rare earth elements, a very unusual metal tenor closely resembling the mixture of raw materials needed for Li-ion battery production. This study reports on the results of a first detailed investigation of this rather unique polymetallic mineralization style, including detailed petrographic and mineralogical studies complemented by bulk rock geochemistry, electron microprobe analyses, and laser ablation inductively coupled mass spectrometry. The mineralized material comprises an oxide assemblage of goethite hematite, hollandite, and lithiophorite that together cement angular fragments of vein quartz. Lithiophorite is the predominant host of Li (3.6–11.1 kg/t), Co (2.5–54.5 kg/t), and Ni (0.2–8.9 kg/t); Cu is contained in similar amounts in hollandite and lithiophorite whereas light rare earth elements (LREE) are mainly hosted in microcrystalline rhabdophane and florencite, which are finely intergrown with the Mn-Fe-oxyhydroxides. 40Ar/39Ar ages (~ 40–34 Ma) of coronadite group minerals coincide with tectonic activity related to the Cenozoic Eger Graben rifting. A low-temperature hydrothermal overprint of pre-existing base metal sulfide-quartz mineralization on fault structures that were reactivated during continental rifting is proposed as the most likely origin of the polymetallic oxyhydroxide mineralization at Eichigt. However, tectonically enhanced deep-reaching fracture-controlled supergene weathering cannot be completely ruled out as the origin of the mineralization.

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Johnson, J. R. Tobias, and Itai Panas. "Water Adsorption and Hydrolysis on Molecular Transition Metal Oxides and Oxyhydroxides." Inorganic Chemistry 39, no. 15 (July 2000): 3181–91. http://dx.doi.org/10.1021/ic991150h.

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Haack, Elizabeth A., and Lesley A. Warren. "Biofilm Hydrous Manganese Oxyhydroxides and Metal Dynamics in Acid Rock Drainage." Environmental Science & Technology 37, no. 18 (September 2003): 4138–47. http://dx.doi.org/10.1021/es026274z.

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Virtasalo, Joonas J., Peter Österholm, and Eero Asmala. "Estuarine flocculation dynamics of organic carbon and metals from boreal acid sulfate soils." Biogeosciences 20, no. 14 (July 20, 2023): 2883–901. http://dx.doi.org/10.5194/bg-20-2883-2023.

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Abstract. Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport from land to sea. The process is particularly relevant for rivers draining boreal acid sulfate soils of western Finland, which are known to deliver large amounts of trace metals with detrimental environmental consequences for the recipient estuaries in the eastern Gulf of Bothnia in the northern Baltic Sea. This is the first study to investigate dissolved metal (Al, Fe, Mn, Co, and Cu) association with flocculating organic particles in the laboratory, by mixing of acidic metal-rich water from acid-sulfate-soil-impacted rivers and particle-free artificial seawater. Water samples were collected in April 2021 from the Laihianjoki and Sulvanjoki rivers in western Finland. Experiments with an in situ laser-diffraction-based particle size distribution sensor and a multiparameter water quality sonde were run to continuously monitor the development of a suspended particle pool over the salinity gradient from 0 to 6, corresponding to the salinity range observed in these estuarine systems. Flocculator experiments with discrete salinity treatments were carried out to investigate metal behaviour with the collection of flocculated material on glass fibre filters. Filtrate was analysed for coloured dissolved-organic-matter absorbance and fluorescence for the characterization of potential changes in the organic matter pool during the flocculation process. Retentate on the filter was subjected to persulfate digestion of organic particles and metal oxyhydroxides (pH < 2.3), and the digestion supernatants were analysed for metal concentrations. The laboratory experiments showed strong transfer of Al and Fe already at a salinity of 0–2 to newly formed organically dominated flocs that were generally larger than 80 µm. Very strong coupling between the decrease in humic fluorescence and the increase in organically bound Al demonstrated that Al transfer to the flocs was stronger than that of Fe. The flocs in the suspended particle pool were complemented by a smaller population of Al- and Fe-oxyhydroxide-dominated flocculi (median size of 11 µm) after pH exceeded ca. 5.5. Cobalt and Mn transfer to the particle pool was weak, although some transfer to Mn oxyhydroxides as well as Co association with the flocs took place. Up to 50 % of Cu was found to be bound to humic substances in the flocs in the river waters, and this proportion did not significantly change during mixing with seawater. The findings of this study demonstrate that salinity and pH are important independent but connected controls of the flocculation behaviour of dissolved metals from boreal acid sulfate soils and the seaward transport and environmental consequences of the metals in the marine environment.

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Li, Chao, Weiyu Song, Zhenjun Sun, Gang Hu, Xiaojun Yuan, and Shuh-Ji Kao. "Controls on Critical Metal Enrichments in Ferromanganese Nodules from the Philippine Sea, at Water Depths of 4400–6000 m." Minerals 13, no. 4 (April 7, 2023): 522. http://dx.doi.org/10.3390/min13040522.

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Enrichments of critical metals in ferromanganese (Fe–Mn) nodules have received increasing attention in both deep-sea research and mineral exploration. To better assess the controls on the resource potential of Fe–Mn nodules, we conducted a comprehensive and detailed study of twelve nodules from the Philippine Sea collected from water depths of 4400 to 6000 m by investigating their microstructures, bulk geochemistry, and in situ Fe–Mn oxyhydroxide geochemistry, using XRF, ICP-MS, EMPA, and LA-ICP-MS coupled with BSE images. We successfully resolved different controls on the element enrichments, of which significant selective enrichment of metal elements in seawater is similar to that of typical hydrogenetic nodules. An enhanced supply of iron hydroxide due to calcite dissolution resulted in a dilution effect on Co, Ni, and Mn but an enrichment effect on rare earth elements plus yttrium (REE + Y) and Fe in nodules near topographic highs close to the carbonate compensation depth. While the supply of diagenetic Mn resulted in a dilution on Co and REE + Y, it resulted in enrichment on Ni, Cu, Li, and Mn on nodules on the seafloor. Moreover, via micro-layer analyses we confirmed the growth rate is a major determinant for the correlations of Co and REE with Fe-oxyhydroxides in these Philippine Sea nodules.

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Dai, Yuming, Hajera Gul, Chao Sun, Linghua Tan, Yue Guo, Waseem Raza, Arshad Hussain, et al. "Ultrafast synthesizing nanoflower-like composites of metal carbides and metal oxyhydroxides towards high-performance supercapacitors." Electrochimica Acta 438 (January 2023): 141575. http://dx.doi.org/10.1016/j.electacta.2022.141575.

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Costa, Dominique, Joelle Guignard, Roger Zalma, and Henri Pezerat. "Production of Free Radicals Arising from the Surface Activity of Minerals and Oxygen. Part I. Iron Mine Ores." Toxicology and Industrial Health 5, no. 6 (December 1985): 1061–78. http://dx.doi.org/10.1177/074823378900500613.

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The excess incidence of lung cancers observed in many metal mines probably is not only correlated with radioactivity but also with the inhaled dusts. In an attempt to determine a possible mechanism of carcinogenicity related to the surface activity of dusts, using the spin-trapping agent and ESR spectroscopy, one can demonstrate that some mineral dusts from iron ore mines are very active in an oxidative process in aqueous medium, implying the formation of radical oxygen species on reducing surface sites of the solid. This reducing surface activity of the dusts depends on the presence of Fe2+ ion in the lattice and on the process of activation and passivation of the surface sites. The more simple process of activation is the dissolution of the oxidized coating on the particle surface. Among the oxides, oxyhydroxides, carbonates, and silicates, the magnesium-iron phyllosilicates (chlorite, biotite, berthierine) appear the most active. The siderite FeCO3 is also active, but the iron oxides and oxyhydroxides are generally nonactive.

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Reiller, P. E. "Modelling metal–humic substances–surface systems: reasons for success, failure and possible routes for peace of mind." Mineralogical Magazine 76, no. 7 (December 2012): 2643–58. http://dx.doi.org/10.1180/minmag.2012.076.7.02.

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AbstractIron oxides and oxyhydroxides are commonly of considerable importance in the sorption of ions onto rocks, soils and sediments. They can be the controlling sorptive phases even if they are present in relatively small quantities. In common with other oxides and clay minerals, the sorption pH-edge of metals is directly linked to their hydrolysis: the higher the residual charge on the metal ion, the lower the pH-edge. Modelling of this process has been successfully carried out using different microscopic or macroscopic definitions of the interface (e.g. surface complexation or ion exchange models that may or may not include mineralogical descriptions). The influence of organic material on the sorption of many metals is of significant. This organic material includes simple organic molecules and more complex exopolymeric substances (e.g. humic substances) produced by the decay of natural organic matter. Sorption of this organic material to mineral surfaces has been the subject of a large body of work. The various types of organic substances do not share the same affinities for mineral surfaces in general, and for iron oxides and oxyhydroxides in particular. In those cases in which successful models of the component binary systems (i.e. metal–surface, metal–organic, organic–surface) have been developed, the formation of mixed surface complexes, the evolution of the surface itself, the addition order in laboratory systems, and the evolution of natural organic matter fractions during sorption, have often precluded a satisfactory description of metal–surface–organic ternary systems over a sufficiently wide range of parameter values (i.e. pH, ionic strength, concentration of humic substances). This manuscript describes the reasons for some successes and failures in the modelling of the ternary systems. Promising recent advances and possible methods of providing more complete descriptions of these intricate systems are also discussed.

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Herbert, R. B. "Zinc immobilization by zerovalent Fe: surface chemistry and mineralogy of reaction products." Mineralogical Magazine 67, no. 6 (December 2003): 1285–98. http://dx.doi.org/10.1180/0026461036760165.

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AbstractIn bioreactor systems for the treatment of metal-contaminated water, pretreatment with zerovalent Fe can be exploited for oxygen consumption and H2 production. In this study, a column experiment is used to investigate the changes in surface chemistry and solid phase products that result from the reaction of a Zn-sulphate-lactate solution with zerovalent Fe filings. The results of this study indicate that zerovalent Fe is very effective in immobilizing dissolved Zn with a porewater residence time of 1.3 –3.1 days. A combination of X-ray diffractometry, X-ray photoelectron spectroscopy, and mineral equilibria calculations indicates that Zn precipitates as Zn(OH)2 and zincite at pH 9 –10. At pH ≈6, Zn primarily adsorbs to abundant ferric oxyhydroxides, although incorporation in green rust is also considered. During the course of the experiment, the surface mineralogy changes from magnetitelepidocrocite- goethite to green rust-akaganéite-goethite. The results suggest that the zerovalent Fe surface becomes passivated by a surface film of ferric oxyhydroxides, green rust and organic material, so that the rate of electron transfer and proton consuming reactions (i.e. oxygen consumption, H2 generation) declines, resulting in a decrease in solution pH.

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Krivina, Raina A., Yingqing Ou, Qiucheng Xu, Liam P. Twight, T. Nathan Stovall, and Shannon W. Boettcher. "Oxygen Electrocatalysis on Mixed-Metal Oxides/Oxyhydroxides: From Fundamentals to Membrane Electrolyzer Technology." Accounts of Materials Research 2, no. 7 (July 13, 2021): 548–58. http://dx.doi.org/10.1021/accountsmr.1c00087.

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Sun, Xun, Xin Guan, Hao Feng, Dengchao Zheng, Wenli Tian, Chengyi Li, Chuiyu Li, Minglei Yan, and Yadong Yao. "Enhanced activity promoted by amorphous metal oxyhydroxides on CeO2 for alkaline oxygen evolution reaction." Journal of Colloid and Interface Science 604 (December 2021): 719–26. http://dx.doi.org/10.1016/j.jcis.2021.06.149.

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Davranche, Mélanie, and Jean-Claude Bollinger. "Release of Metals from Iron Oxyhydroxides under Reductive Conditions: Effect of Metal/Solid Interactions." Journal of Colloid and Interface Science 232, no. 1 (December 2000): 165–73. http://dx.doi.org/10.1006/jcis.2000.7177.

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Chapman, Peter M., Feiyue Wang, Colin Janssen, Guido Persoone, and Herbert E. Allen. "Ecotoxicology of metals in aquatic sediments: binding and release, bioavailability, risk assessment, and remediation." Canadian Journal of Fisheries and Aquatic Sciences 55, no. 10 (October 1, 1998): 2221–43. http://dx.doi.org/10.1139/f98-145.

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Major metal-binding phases in the aerobic layer of sediments are iron and manganese oxyhydroxides (FeOOH and MnOOH) and particulate organic carbon (POC). The acid-volatile sulfide (AVS) model proposed for predicting nontoxicity from metals-contaminated sediments is only applicable to anaerobic sediments. In other sediments, normalization by POC or FeOOH and MnOOH may be predictive, but binding constants are not well understood. Metal mobilization is enhanced by ligand complexation and oxidation of anaerobic sediments. Free metal ion is the most bioavailable species, but other labile metal species and nonchemical variables also determine metal bioavailability; biotic site binding models have shown promise predicting toxicity for systems of differing chemistry. Hazard identification and ecological risk assessment (ERA) depend on determining bioavailability, from water (overlying, interstitial) and food, which can be done prospectively (e.g., normalized sediment chemistry, laboratory bioassays) or retrospectively (e.g., in situ bioassays, field studies). ERA of sediment-bound metals requires primary emphasis on toxicity and consideration of the three separate transformation processes for metals in the aquatic environment, the differences between essential and nonessential metals, the complex interactions that control bioavailability, adaptation, which may occur relatively simply without appreciable cost to the organism, weight of evidence, and causality.

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Deliyanni, E., D. Bakoyannakis, A. Zouboulis, and K. Matis. "Development and study of iron-based nanoadsorbents." Journal of Mining and Metallurgy, Section B: Metallurgy 40, no. 1 (2004): 1–9. http://dx.doi.org/10.2298/jmmb0401001d.

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The application of an innovative, simple and low cost method was tested for the preparation of nanocrystalline iron hydroxides and oxyhydroxides; different iron precursors have been earlier used and combined to different volatile precipitating agents. The examined in the present product, akagan?ite [?-FeO(OH)], had high surface area and definite pore size distribution. The produced materials were examined in detail (i.e. by powder X-ray diffraction, TEM and nitrogen sorption measurement). Main aim of this study was to evaluate the efficiency of the prepared material in the removal of heavy and toxic metal cations, like Cd(II), from aqueous solutions; cadmium constitutes a priority pollutant. Sorption was found to depended on the solution pH and its ionic strength. Typical isotherm models were applied and calculated the values of maximum adsorbent capacity for the metal as well as that of the enthalpy change during the removal process.

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Durin, B., B. Béchet, M. Legret, and P. Le Cloirec. "Role of colloids in heavy metal transfer through a retention-infiltration basin." Water Science and Technology 56, no. 11 (December 1, 2007): 91–99. http://dx.doi.org/10.2166/wst.2007.762.

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Runoff waters from a main bridge near Nantes (France), surface waters and pore waters in the infiltration basin collecting runoff were analysed after filtration and ultrafiltration to investigate the role of colloids in the transfer of trace metals (Zn, Cu and Pb) from the road to the groundwater. The role of the basin in mitigation of the variations of physico-chemical parameters and chemical elements concentrations was confirmed. An increase of mobile colloidal phase by comparison with runoff and high concentrations of trace metals were observed in pore waters of the sediment. Up to 100% of Pb and 60% of Cu and Zn may be associated to compounds having a molecular weight above 5 kDaltons. Principal component analysis outlined the variability of the influence of the physico-chemical parameters on trace metals concentrations for the different waters. Speciation calculations pointed out the potential precipitation of Fe and Al oxyhydroxides in all kind of waters.

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Yusin, S. I., and O. V. Karunina. "Synthesis and Characterization of Supercapacitor Electrode Materials Based on Carbon Fiber Materials and Metal Oxyhydroxides." Inorganic Materials: Applied Research 9, no. 5 (September 2018): 954–59. http://dx.doi.org/10.1134/s2075113318050325.

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Chaudhary, Mohit, Shweta Rawat, Nishant Jain, Amit Bhatnagar, and Abhijit Maiti. "Chitosan-Fe-Al-Mn metal oxyhydroxides composite as highly efficient fluoride scavenger for aqueous medium." Carbohydrate Polymers 216 (July 2019): 140–48. http://dx.doi.org/10.1016/j.carbpol.2019.04.028.

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Alburaih, H. A., Sumaira Manzoor, M. Abdullah, M. N. Ashiq, Salma Aman, Sergei V. Trukhanov, Tatiana I. Zubar, Zhipeng Sun, T. A. Taha, and Alex V. Trukhanov. "Electro-oxidation reconstitution of aluminium copper MOF-derived metal oxyhydroxides for a robust OER process." RSC Advances 13, no. 13 (2023): 8736–42. http://dx.doi.org/10.1039/d2ra07661f.

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Lin, Zhiqun. "(Invited) Operando Unraveling Photothermal-Promoted Dynamic Active Sites Generation in Spinel Oxide for Markedly Enhanced Oxygen Evolution." ECS Meeting Abstracts MA2022-02, no. 48 (October 9, 2022): 1848. http://dx.doi.org/10.1149/ma2022-02481848mtgabs.

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As the electrochemical reconstruction into highly active species is anticipated to arise under the oxidative conditions, activating and tailoring the surface reconstruction via a rational and effective strategy is pivotal to improve the oxygen evolution reaction (OER) activity. In this work, we advance a robust process, that is, the photothermal effect originated from the spinel oxide catalyst, to render its dynamic transition into active metal oxyhydroxides species that triggers highly efficient oxygen evolution. Significantly, the reaction kinetics of OER are improved due to the lowered activation energy, as modulated by the photothermal energy-promoted surface reconstruction. More importantly, the operando Raman spectroelectrochemistry study and first-principle calculation collectively unveil the mechanism of photothermal-assisted enhancement in OER reaction.

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Stelmachowski, Paweł, Joanna Duch, David Sebastián, María Jesús Lázaro, and Andrzej Kotarba. "Carbon-Based Composites as Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media." Materials 14, no. 17 (August 31, 2021): 4984. http://dx.doi.org/10.3390/ma14174984.

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This review paper presents the most recent research progress on carbon-based composite electrocatalysts for the oxygen evolution reaction (OER), which are of interest for application in low temperature water electrolyzers for hydrogen production. The reviewed materials are primarily investigated as active and stable replacements aimed at lowering the cost of the metal electrocatalysts in liquid alkaline electrolyzers as well as potential electrocatalysts for an emerging technology like alkaline exchange membrane (AEM) electrolyzers. Low temperature electrolyzer technologies are first briefly introduced and the challenges thereof are presented. The non-carbon electrocatalysts are briefly overviewed, with an emphasis on the modes of action of different active phases. The main part of the review focuses on the role of carbon–metal compound active phase interfaces with an emphasis on the synergistic and additive effects. The procedures of carbon oxidative pretreatment and an overview of metal-free carbon catalysts for OER are presented. Then, the successful synthesis protocols of composite materials are presented with a discussion on the specific catalytic activity of carbon composites with metal hydroxides/oxyhydroxides/oxides, chalcogenides, nitrides and phosphides. Finally, a summary and outlook on carbon-based composites for low temperature water electrolysis are presented.

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Gao, Likun, Xun Cui, Zewei Wang, Christopher D. Sewell, Zili Li, Shuang Liang, Mingyue Zhang, Jian Li, Yingjie Hu, and Zhiqun Lin. "Operando unraveling photothermal-promoted dynamic active-sites generation in NiFe2O4 for markedly enhanced oxygen evolution." Proceedings of the National Academy of Sciences 118, no. 7 (February 8, 2021): e2023421118. http://dx.doi.org/10.1073/pnas.2023421118.

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The ability to develop highly active and low-cost electrocatalysts represents an important endeavor toward accelerating sluggish water-oxidation kinetics. Herein, we report the implementation and unraveling of the photothermal effect of spinel nanoparticles (NPs) on promoting dynamic active-sites generation to markedly enhance their oxygen evolution reaction (OER) activity via an integrated operando Raman and density functional theory (DFT) study. Specifically, NiFe2O4 (NFO) NPs are first synthesized by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors. Upon the near-infrared light irradiation, the photothermal heating of the NFO-based electrode progressively raises the temperature, accompanied by a marked decrease of overpotential. Accordingly, only an overpotential of 309 mV is required to yield a high current density of 100 mA cm−2, greatly lower than recently reported earth-abundant electrocatalysts. More importantly, the photothermal effect of NFO NPs facilitates surface reconstruction into high-active oxyhydroxides at lower potential (1.36 V) under OER conditions, as revealed by operando Raman spectroelectrochemistry. The DFT calculation corroborates that these reconstructed (Ni,Fe)oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced over pure NFO without surface reconstruction. Given the diversity of materials (metal oxides, sulfides, phosphides, etc.) possessing the photo-to-thermal conversion, this effect may thus provide a unique and robust platform to boost highly active surface species in nanomaterials for a fundamental understanding of enhanced performance that may underpin future advances in electrocatalysis, photocatalysis, solar-energy conversion, and renewable-energy production.

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Grybos, Malgorzata, Mélanie Davranche, Gérard Gruau, and Patrice Petitjean. "Is trace metal release in wetland soils controlled by organic matter mobility or Fe-oxyhydroxides reduction?" Journal of Colloid and Interface Science 314, no. 2 (October 2007): 490–501. http://dx.doi.org/10.1016/j.jcis.2007.04.062.

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Mann, H., and W. S. Fyfe. "Metal uptake and Fe-, Ti-oxide biomineralization by acidophilic microorganisms in mine-waste environments, Elliot Lake, Canada." Canadian Journal of Earth Sciences 26, no. 12 (December 1, 1989): 2731–35. http://dx.doi.org/10.1139/e89-234.

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Acidic effluent containing enhanced concentrations of toxic heavy metals discharges from a cumulative total of 104 ha of mine-tailings waste in Canada. Communities of acidophilic microorganisms, specifically the unicellular alga Euglena sp. and bacteria, thrive in many of the hostile, low-pH effluent environments, which are otherwise devoid of life. The micro organisms concentrate aqueous dissolved metals onto cell walls and at intracellular sites, during the life cycle, and strongly bind metals during early diagenesis. A sequence is observed in which amorphous Fe and Ti concentrated at cell walls are progressively transformed to microcrystalline aggregates of goethite, ferrihydrite, maghemite, magnetite, haematite, lepidocrocite, and ilmenite. The bioprecipitated Ti- and Fe-oxides and oxyhydroxides act as scavengers for heavy metals such as Cu, Pb, Zn, Ni, Cd, and Th. Acidophilic microorganisms play a central role in the toxic-metal budget of mine-tailings waste by efficiently sequestering aqueous metals and by promoting nucleation of oxide minerals whose inorganic formation is kinetically inhibited, thereby retarding toxic-metal dispersion into the natural environment.

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Tateishi, Yuko, Hisahiro Einaga, and Yasutake Teraoka. "Preparation and Characterization of Golden-Colored Pigments Based on Silver Coated with Metal Oxides." Advanced Materials Research 47-50 (June 2008): 1462–65. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.1462.

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The present study aimed at the development of new artificial golden-colored pigments which are thermally stable up to 900 oC and can be used for coloring ceramics wares. Silver was used as a base material with bright metallic luster. Silver with the larger lamellar structure was indispensable to maintain the metallic luster, and it was successfully obtained by the heat-treatment of as-obtained silver powder at 200-400 oC in air and subsequently dry ball-milling at 300 rpm for 1 h. The surface of the lamellar-structured silver was coated with small particles of hydroxides, oxyhydroxides and oxides of Fe, Co, Ni, Ce and Pr. Appearance of golden color depended on the combination of metal species and heat-treatment temperature, and CeO2-coated silver gave golden color after calcination at 800 and 900 oC. The golden color of CeO2-coated silver could be controlled by the loading amount and particle size of CeO2 for color tone and relative area of naked surface of Ag for luster.

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Little, Brenda J., Jason S. Lee, and Tammie L. Gerke. "The Relationship Between Iron Oxides/Oxyhydroxides and Toxic Metal Ions in Drinking Water Distribution Systems—A Review." CORROSION 73, no. 2 (February 2017): 138–43. http://dx.doi.org/10.5006/2162.

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Stanisic, Svetlana, Ljubisa Ignjatovic, Ivan Andjelkovic, Milica Stevic, Aleksandra Tasic, and Marjetka Savic-Bisercic. "The ultrasound assisted extraction of matrix elements and heavy metal fractions associated with Fe, Al and Mn oxyhydroxides from soil." Journal of the Serbian Chemical Society 77, no. 9 (2012): 1287–300. http://dx.doi.org/10.2298/jsc110929209s.

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The single agent extractions of major and trace metals from soil sample were conducted by means of rotary mixer and ultrasonic bath with sonication time of 10, 20, 30, 40 and 50 min. The sequential extraction according to the BCR scheme was undertaken. The obtained soil extracts were analyzed by ICP-OES and according to the results the rotary mixer assisted extraction was more efficient in the case of alkaline-earth elements. However, by the use of ultrasound several times higher amounts of matrix elements (Fe, Al and Mn) and heavy metals predominantly associated with Fe, Al and Mn oxyhydroxides were extracted. The increase of the sonication time failed to improve extraction yields. The changes of the conductivity, pH, oxidoreduction potential, particle size diameter and zeta potential of colloid particles, with the sonication time increase were measured. The extraction mechanism and expressed selectivity of ultrasound is discussed and explanation is suggested.

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Song, Huijun, Jingjing Li, Guan Sheng, Yinling Zhang, Ahmad Azmin Mohamad, Juan Luo, Zhangnan Zhong, and Wei Shao. "Construction of Core–Shell CoMoO4@γ-FeOOH Nanosheets for Efficient Oxygen Evolution Reaction." Nanomaterials 12, no. 13 (June 28, 2022): 2215. http://dx.doi.org/10.3390/nano12132215.

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The oxygen evolution reaction (OER) occurs at the anode in numerous electrochemical reactions and plays an important role due to the nature of proton-coupled electron transfer. However, the high voltage requirement and low stability of the OER dramatically limits the total energy converting efficiency. Recently, electrocatalysts based on multi-metal oxyhydroxides have been reported as excellent substitutes for commercial noble metal catalysts due to their outstanding OER activities. However, normal synthesis routes lead to either the encapsulation of excessively active sites or aggregation during the electrolysis. To this end, we design a novel core–shell structure integrating CoMoO4 as support frameworks covered with two-dimensional γ-FeOOH nanosheets on the surface. By involving CoMoO4, the electrochemically active surface area is significantly enhanced. Additionally, Co atoms immerge into the γ-FeOOH nanosheet, tuning its electronic structure and providing additional active sites. More importantly, the catalysts exhibit excellent OER catalytic performance, reducing overpotentials to merely 243.1 mV a versus 10 mA cm−2. The current strategy contributes to advancing the frontiers of new types of OER electrocatalysts by applying a proper support as a multi-functional platform.

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Rogan Šmuc, Nastja, Nives Kovač, Žan Hauptman, Andrej Šmuc, Matej Dolenec, and Aleš Šoster. "A Detailed Insight into the Detrital and Diagenetic Mineralogy of Metal(oid)s: Their Origin, Distribution and Associations within Hypersaline Sediments." Minerals 11, no. 11 (October 22, 2021): 1168. http://dx.doi.org/10.3390/min11111168.

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Hypersaline environments are among the most vulnerable coastal ecosystems and are extremely noteworthy for a variety of ecological reasons. Comprehensive assessment of metal(oid) contamination in hypersaline sediments from Sečovlje (Northern Adriatic, Slovenia) was addressed by introducing the detrital and diagenetic mineralogy and geochemical properties within the solid sediment material. Close associations between Fe/Mn oxides and oxyhydroxides with As, Cr, Ni, Pb and Zn, and between organic matter with Cu, Pb and Zn were confirmed using X-ray powder diffraction, SEM-EDS and ICP emission spectrometry analysis. Possible incorporation or adsorption on the crystal lattices of clay minerals (As, Cr, Pb, Sn and Zn), halite (As) and aragonite/calcite (Cd, Cu, Pb, Sr and Zn) were also detected. All presented correlations were highlighted by various statistical analyses. The enrichment factor (EF) values showed a low degree of anthropogenic burden for As, Bi, Hg and Zn, while Cd, Cr, Cu, Ni, Pb, Sn and Sr originated from the geological background. These results emphasise that a detailed mineralogical and geochemical characterisation of solid (especially detrital and diagenetic) sediment particles is crucial in further understanding the metal(oid) translocation within the hypersaline ecosystems.

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FÄLTMARSCH, R., P. ÖSTERHOLM, and M. GREGER. "Metal concentrations in oats (Avena sativa L.) grown on acid sulphate soils." Agricultural and Food Science 18, no. 1 (December 4, 2008): 45. http://dx.doi.org/10.2137/145960609788066843.

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The aim of the study was to investigate the impact of soil chemistry on the concentrations of Co, Ni, Zn, Mn, Cu and Fe in oats (Avena sativa L. cv. Fiia) grown on Finnish acid sulphate (AS) soils with varying geochemical characteristics. Twenty two soil profiles, which were sampled to a depth of 1 m (five 20 cm section splits), and 26 composite oat grain samples were collected on a total of five fields. The concentrations of Co, Ni, Zn and Mn in the grains were correlated with the NH4Ac-EDTA-extractable concentrations in the soils. However, as these four chalcophilic metals are in general easily lost to drains and not retained as a large pool in the soil in easily-extractable form, also the concentrations in the oats were not in general elevated as compared with average values on other soils. On one of the fields, however, the Co and Ni concentrations in the soil, and thus also in the oats, were clearly elevated. Copper and Fe displayed no correlation between the soil and oat concentrations, indicating that the plant-uptake mechanisms are much more important than variations in geochemistry. It was suggested that the NH4Ac-EDTA solution was not efficient in extracting Fe and Cu, which shows that these metals are bound in relatively immobile oxyhydroxides.;

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Chen, Zongkun, Xingkun Wang, Sascha Keßler, Qiqi Fan, Minghua Huang, and Helmut Cölfen. "Synthesis of hierarchical transition metal oxyhydroxides in aqueous solution at ambient temperature and their application as OER electrocatalysts." Journal of Energy Chemistry 71 (August 2022): 89–97. http://dx.doi.org/10.1016/j.jechem.2022.02.042.

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Prange, Micah P., Daniel J. Pope, and Kevin M. Rosso. "Electronic and Vibrational Contributions to the Bulk Stabilities of Trivalent 3d Transition Metal Oxyhydroxides from Electronic Structure Calculations." Journal of Physical Chemistry C 124, no. 13 (March 11, 2020): 7500–7510. http://dx.doi.org/10.1021/acs.jpcc.9b12057.

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Stegemeier, J. P., B. C. Reinsch, C. J. Lentini, J. G. Dale, and C. S. Kim. "Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: II. Temperature and time." Geochimica et Cosmochimica Acta 148 (January 2015): 113–29. http://dx.doi.org/10.1016/j.gca.2014.08.031.

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Akintomide, Omolola A., Segun A. Adebayo, Alexandra S. Trahan, Elizabeth Chamberlain, and Karen H. Johannesson. "Investigating the Potential Impact of Louisiana Coastal Restoration on the Trace Metal Geochemistry of Constructed Marshlands." Soil Systems 4, no. 3 (September 5, 2020): 55. http://dx.doi.org/10.3390/soilsystems4030055.

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Coastal restoration through diversion of suspended sediments from the Lower Mississippi River (LMR) into hydrologically isolated marshlands of Mid-Barataria Bay and Mid-Breton Sounds in southern Louisiana has the potential to mobilize lead (Pb), and other trace elements. We investigate the potential impact(s) of the diversion on marsh porewater through analysis of modern riverbank and suspended sediments, compared to sediments from pre-industrial deltaic deposits of LMR. Sequential extraction methods were used to evaluate Pb, cobalt (Co), copper (Cu), nickel (Ni), and zinc (Zn) in the sediments. Our results show that metal contents are higher (e.g., 8- to 10-fold for Pb) in the modern sediments relative to pre-industrial deposits. Also, the reducible fraction, presumably iron/manganese (Fe/Mn) oxides/oxyhydroxides, is the chief reservoir of environmentally available metals. The substantially higher trace metal contents of the modern relative to pre-industrial sediments suggest that the modern sediments contain a sizeable amount of anthropogenic contributions. Furthermore, the concentration of the trace metals in the reducible fraction suggests bioavailability to marsh organisms upon reductive dissolution within the planned, constructed coastal marshes. Still, additional sediment samples from the marshlands during the diversion implementation phase will be necessary to support the preliminary findings in this contribution as it affects coastal marshes and vital local fisheries.

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Szczerba, W., M. Schneider, J. Żukrowski, A. Guilherme Buzanich, H. Riesemeier, M. Sikora, and K. Mandel. "Spectroscopic Study of the Role of Metal Ions in the Adsorption Process of Phosphate in Nanoscaled Adsorbers Based on Metal (Zn/Fe/Zr) Oxyhydroxides." Journal of Physical Chemistry C 121, no. 45 (November 2017): 25033–42. http://dx.doi.org/10.1021/acs.jpcc.7b04773.

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Virtasalo, Joonas J., Peter Österholm, Aarno T. Kotilainen, and Mats E. Åström. "Enrichment of trace metals from acid sulfate soils in sediments of the Kvarken Archipelago, eastern Gulf of Bothnia, Baltic Sea." Biogeosciences 17, no. 23 (December 7, 2020): 6097–113. http://dx.doi.org/10.5194/bg-17-6097-2020.

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Abstract. Rivers draining the acid sulfate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area and the relevant metal transport mechanisms have been less studied. This study investigates the spatial and temporal distribution of metals in sediments at nine sites in the Kvarken Archipelago, which is the recipient system of Laihianjoki and Sulvanjoki rivers that are impacted by acid sulfate soils. The contents of Cd, Co, Cu, La, Mn, Ni, and Zn increased in the cores during the 1960s and 1970s as a consequence of intensive artificial drainage of the acid sulfate soil landscape. Metal deposition has remained at high levels since the 1980s. The metal enrichment in sea floor sediments is currently visible at least 25 km seaward from the river mouths. Comparison with sediment quality guidelines shows that the metal contents are very likely to cause detrimental effects on marine biota more than 12 km out from the river mouths. The dynamic sedimentary environment of the shallow archipelago makes these sediments potential future sources of metals to the ecosystem. Finally, the strong association of metals and nutrients in the same sediment grain size class of 2–6 µm suggests that the transformation of dissolved organic matter and metals to metal–organic aggregates at the river mouths is the key mechanism of seaward trace metal transport, in addition to co-precipitation with Mn oxyhydroxides identified in previous studies. The large share of terrestrial organic carbon in the total organic C in these sediments (interquartile range – 39 %–48 %) highlights the importance of riverine organic matter supply. These findings are important for the estimation of environmental risks and the management of biologically sensitive coastal sea ecosystems.

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Boettcher, Shannon W. "(Invited) Cooperative Fe Sites on Transition Metal (Oxy)Hydroxides for High Oxygen Evolution Activity." ECS Meeting Abstracts MA2022-01, no. 23 (July 7, 2022): 1167. http://dx.doi.org/10.1149/ma2022-01231167mtgabs.

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Heterogeneous electrocatalysts for the oxygen evolution reaction (OER) are complicated materials with dynamic structures. They exhibit potential-induced phase transitions, potential-dependent electronic properties, variable oxidation and protonation states, and disordered local/surface phases. These properties make understanding the OER, and ultimately designing higher-efficiency catalysts, challenging. Measurements of intrinsic activity show that, by far, the most-active phases for OER under alkaline conditions are Fe-containing mixed-metal oxyhydroxides, but exactly how they function remains controversial. I will discuss our work to understand the key properties of these catalysts, including morphology, composition, and molecular/electronic structure, and how they evolve and are dynamic under active catalytic conditions. Specifically, I will highlight new work where we have been able to systematically control the concentration of surface Fe species on NiOOH and CoOOH host structures. We discover that the per-Fe turn-over frequency (TOFFe) for the OER increases nearly linearly with the Fe concentration, providing clear evidence for cooperative effects between Fe atoms and suggestive of a mechanism involving multiple Fe sites that is supported by density functional theory calculations. In sum, these concepts inform design strategies for higher-performance catalyst architectures and for their incorporation into practical electrolyzer devices to make clean hydrogen fuel from inexpensive renewable electricity for green long-distance transportation and long-duration energy storage.

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Liu, Guo, Pourret, Chen, and Yuan. "Role of Manganese Oxyhydroxides in the Transport of Rare Earth Elements Along a Groundwater Flow Path." International Journal of Environmental Research and Public Health 16, no. 13 (June 26, 2019): 2263. http://dx.doi.org/10.3390/ijerph16132263.

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Rare earth elements (REE) are known to be emerging contaminants in hydrosphere, but roles of hydrous manganese oxyhydroxides (HMO) in REE transport in groundwater remains unknown. In this study, groundwater was sampled along a flow path in the North China Plain to determine the behavior of REE surface complexation to HMO by a modeling and field study approach. Results show that the proportion of neodymium (Nd) complexed by HMO ranges from 0.2% to 95.8%, and from 0.3% to 99.6% in shallow groundwater and deep groundwater, respectively. The amount of complexed REE increases along the flow path. REE bound to HMO exhibit decreasing trends with increasing atomic number. The process was determined to be independent of pH, HMO content, and metal loading. This finding further demonstrates HMO-REE complexation plays a key role in transport of REE in groundwater through preferential scavenging of light REE (LREE) over heavy REE (HREE). Nevertheless, carbonate ligands appear to be robust competitors in reducing the amount of REE sorbed to HMO when solution pH rises above 8.0. Assuming that 50% of Mn concentration occurs as HMO, the amount of complexed REE was predicted to show a more marked decrease in LREE compared to that of HREE.

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Journal articles on the topic 'Metal Oxyhydroxides'

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