Literatura científica selecionada sobre o tema "Ammonia-borane oxidation reaction (ABOR)"

Cu doped Ni(PO3)2 was applied as an electrocatalyst to ABOR for the first time, which showed an excellent electrocatalytic activity due to the optimized electronic structure and the increased active sites induced by the Cu doping.

A Co(II) PNNH pincer catalyst system for the highly E-selective transfer-semihydrogenation of internal alkynes using ammonia borane and MeOH as the hydrogen source is described. The reaction is proposed to occur via the Co(ii) oxidation state.

Traditionally, fertilizers have been produced with ammonia (which is produced from the Haber-Bosch process) as the main feedstock. The Haber-Bosch process which requires the reaction of atmospheric nitrogen with hydrogen at high temperature and pressure is energy and cost intensive [1]. Only about half fraction of reactive nitrogen in the produced ammonia fertilizers is used by the plants with the rest remaining in the soil as waste [2]. These ‘excess’ nutrients find a way into water bodies and wastewater treatment plants (WWTP) as run-offs and this poses a big threat to the nitrogen balance in the environment. This research aims to recover these nutrients primarily nitrogen and phosphorous to produce a low-cost fertilizer of at least compatible potency as commercial fertilizers. Waste Activated Sludge (WAS), the solids obtained from the primary and secondary clarifiers in WWTPs contain a wide range of organic compounds as well as valuable nutrients such as phosphorus and nitrogen which can account for up to 4% and 9% of dry sludge, respectively [3]. The leachate from landfills can release these nutrients into the environment, raising serious environmental pollution concerns. Therefore, recovering nutrients from WAS presents a significant opportunity towards a nitrogen circular economy. Most of the research in sludge treatment are exclusively focused on improving biological treatment processes like anaerobic digestion and composting which can take anywhere from a month to three months and thermal treatments such as pyrolysis and hydrothermal treatments [4] which are energy intensive and expensive. This work provides a novel approach to recover nutrients at low energy consumption with nickel based electrocatalysts [5]. The hypothesis here is that the alkaline medium will help break the floc structure of the sludge to release the proteins and other organic compounds which will then be hydrolyzed by the nickel oxyhydroxide (NiOOH) group formed on the electrode surface by application of a small voltage sufficient to form NiOOH. The NiOOH is consumed quickly on the surface of the electrode by the organic nitrogen present in solution [6]. Hence, alternating the polarity between two identical nickel electrodes will ensure that NiOOH is always present on the electrode surface. The approach square wave potential pulses also enhance the desorption of species and clean the surface of the electrodes, especially when dealing with a complex mixture of organics that can polymerize in the surface of electrodes during the oxidation/reduction process. The effect of frequency of polarity oscillation, electrode surface area, pH and conductivity on nutrient recovery are being studied and results will be reported at the conference. Since sludge treatment accounts for a sizable portion i.e., close to 60% of wastewater treatment plant operational costs [7], WAS nutrient recovery could also provide economic benefits. This research highlights the potential for electrochemical approaches to address environmental concerns, improve resource efficiency and provide a sustainable solution for sludge management. Acknowledgement This work is funded by the National Science Foundation, EEC Division of Engineering Education and Centers, NSF Engineering Research Center for Advancing Sustainable and Distributed Fertilizer production (CASFER), NSF 20-553 Gen-4 Engineering Research Centers award # 2133576. References Appl M. The Haber-Bosch heritage: The ammonia production technology. In 50th Anniversary of the IFA Technical Conference 1997 Sep 25 (Vol. 25). Spain: Seville. Galloway JN, Aber JD, Erisman JW, Seitzinger SP, Howarth RW, Cowling EB, Cosby BJ. The nitrogen cascade. Bioscience. 2003 Apr 1;53(4):341-56. Bi W, Li Y, Hu Y. Recovery of phosphorus and nitrogen from alkaline hydrolysis supernatant of excess sludge by magnesium ammonium phosphate. Bioresource technology. 2014 Aug 1;166:1-8. Wu B, Dai X, Chai X. Critical review on dewatering of sewage sludge: Influential mechanism, conditioning technologies and implications to sludge re-utilizations. Water research. 2020 Aug 1;180:115912. Jafari, M., Botte, G.G. Electrochemical treatment of sewage sludge and pathogen inactivation. Appl. Electrochem. 51, 119–130 (2021). https://doi.org/10.1007/s10800-020-01481-6 Wang D, Botte GG. In situ X-ray diffraction study of urea electrolysis on nickel catalysts. ECS Electrochemistry Letters. 2014;3(9):H29. Andreoli CV, Von Sperling M, Fernandes F. Sludge treatment and disposal. IWA publishing; 2007.

The development of efficient catalysts for high‐performance ammonia oxidation reaction (AOR) is crucial for direct ammonia fuel cells. However, AOR is severely affected by slow kinetics and the toxicity of reaction intermediates, which reduce the durability of precious metal catalysts. Here, a two‐dimensional carbon dots modified Pt2Pd nanoporous alloy (Pt2Pd‐CDs) is synthesized through the borane morpholine reduction of a platinum palladium oxide nanosheet. The Pt2Pd‐3% CDs (the mass of CDs is 3% of Pt2Pd) exhibits high AOR activity and stability in alkaline media, with an onset potential of 0.41 V vs. RHE, which is 170 mV lower than that of the commercial Pt/C (0.58 V vs. RHE). In addition, after 2000 cycles of accelerated durability testing, the peak mass activity (115.3 A gPGM‐1) decreases by only 25.8%. This enhancement is mainly attributed to the unique advantage of two‐dimensional nanoporous structure with a high electrochemical surface area, and the strong ammonia adsorption and the electron deliver capacity of CDs.

Germanium exhibits superior hole and electron mobility compared with silicon, making it a promising candidate for replacement of silicon in certain future CMOS applications. In such applications, achieving atomically clean Ge surfaces and the subsequent deposition of ultrathin passivation barriers without interfacial reaction are critical. In this study, we present in situ x-ray photoelectron spectroscopy (XPS) investigations of hydrocarbon removal from the Ge surface utilizing atomic oxygen at room temperature, as well as removal of hydrocarbons and of germanium oxide (GeO2) through atomic hydrogen treatment at 350 °C. Subsequently, atomic layer deposition (ALD) was used to create a protective layer of hexagonal boron nitride (h-BN) with an average thickness of 3 monolayers (ML). Tris(dimethylamino)borane and ammonia precursors were utilized at 450 °C for the deposition process. Intermittent in situ XPS analysis during ALD confirmed h-BN growth, stoichiometry, and the absence of interfacial reaction with Ge. XPS analysis after subsequent exposure of the Ge film with a h-BN overlayer of ∼9 Å average thickness to 7.2 × 104 l of atomic O (O3P) at room temperature yielded no evidence of Ge oxidation, with only the surface layer of the h-BN film exhibiting oxidation. These results present a practical and scalable route toward the preparation of clean Ge surfaces and subsequent deposition of protective, nanothin h-BN barriers for subsequent processing.

La production d'énergie électrochimique à partir de combustibles sans carbone a récemment suscité un grand intérêt. Ce manuscrit se concentre sur l'étude du mécanisme de la réaction d'oxydation de l'hydrazine (HHOR) sur des électrodes de Ni et le compare avec ceux des réactions d'oxydation du borohydrure et de l’ammoniac-borane (BOR, ABOR). Les sites métalliques de Ni ont été identifiés comme les sites catalytiques pour la HHOR, la BOR et l'ABOR, tandis que la présence de sites de Ni (hydr)oxydés a un effet négatif sur l'activité sans influencer clairement le mécanisme réactionnel. Sur la base des résultats de calculs DFT, de la modélisation microcinétique et de mesures DEMS en ligne, un mécanisme de la HHOR sur Ni a été proposé. Celui-ci implique la réaction directe de l'hydrazine dissoute avec des espèces Ni-OH adsorbées, formant un intermédiaire N2Hx,ad (x<4), qui est ensuite oxydé électrochimiquement, conduisant à la formation de N2 et d’eau
Electrochemical energy production from carbon-free fuels has recently attracted much attention. This manuscript focuses on studying the mechanism of the hydrazine oxidation reaction (HHOR) on Ni electrodes and comparing it with the ones of the borohydride and ammonia-borane oxidation reactions (BOR, ABOR). Metallic Ni sites were identified as the catalytic sites for the HHOR, BOR, and ABOR, while the presence of Ni (hydr)oxide sites was found to negatively affect activity without a clear influence on the reaction mechanism. Based on the results of DFT calculations, microkinetic modelling, and online DEMS measurements, a mechanism for HHOR on Ni was proposed. It involves the direct reaction of dissolved hydrazine with adsorbed Ni-OH species forming N2Hx,ad (x<4) intermediate, which is subsequently electrochemically oxidized, leading to the formation of N2 and water

(–)-Maoecrystal Z 3 was isolated as a minor constituent from the Chinese medicinal herb Isodon eriocalyx. The synthesis of 3 reported (J. Am. Chem. Soc. 2011, 133, 14964) by Sarah E. Reisman of the California Institute of Technology, featuring as a key step the cyclization of 1 to 2, is a tribute to the power of one-electron reduction for carbon–carbon bond construction. The synthesis began with a Myers alkylation to prepare 6. The amide was reduced to the alcohol with the convenient ammonia–borane complex, and the alcohol was carried on to the iodide 7. The first carbocyclic ring of 3 was prepared by classic chemistry, the condensation of dimethyl malonate 9 with mesityl oxide 8, followed by selective removal of one of the ketone carbonyls. A salt-free Wittig reaction followed by hydrolysis, resolution, and reduction then completed the synthesis of 12. Exposure of 12 to peracid led to the epoxide 13 as an inconsequential mixture of diastereomers. The one-electron Nugent/RajanBabu/Gansäuer protocol was low yielding with methyl acrylate, but dramatically improved when the trifluoroethyl acrylate 14 was used as the acceptor. The lactone 15 was formed as a single diastereomer. Alkylation of 15 with 7 followed by oxidation gave 16, which was deprotected and oxidized to give 1. The cascade cyclization of 1 presumably proceeded by initial one-electron reduction of the more accessible aldehyde. The cyclization of the resulting radical onto the alkene may have been assisted by complexation of the lactone carbonyl with the required second equivalent of SmI2. The Sm enolate so prepared was then added to the second aldehyde to give 2. This cyclization sets one quaternary and three ternary stereogenic centers. Attempted monoprotection of 2 was not successful, so the bis acetate was prepared and ozonized, and the aldehyde was condensed with Eschenmoser’s salt to give 17. Careful monohydrolysis then completed the synthesis of (–)-maoecrystal Z 3