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Electrochemical partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni via coupled oxidation of an interfacing NiAl intermetallic compound for robust hydrogen evolution

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Journal of Energy Chemistry 2023年第7期82卷 560-571,I0012页

作者： Young Hwa Yun Kwangsoo Kim Changsoo Lee Byeong-Seon An Ji Hee Kwon Sechan Lee MinJoong Kim Jongsu Seo Jong Hyeok Park Byung-Hyun Kim Hyun-Seok Cho Hydrogen Research Department Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Computational Science&Engineering Laboratory Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Analysis Center for Energy Research Korea Institute of Energy Research152 Gajeong-roYuseong-guDaejeon 34129Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei University50 Yonsei-roSeodaemun-guSeoul 03722Republic of Korea

Ni-based porous electrocatalysts have been widely used in the hydrogen evolution reaction(HER)in alkaline water electrolysis,and the catalysts are produced by selective leaching of Al from Ni-Al *** is well known that chemical leaching of Ni-Al intermetallic compound(IMC)generates a high surface area in Ni(OH)_(2).However,the Ni(OH)_(2) produced by leaching the Ni-Al intermetallic compound retards the hydrogen evolution reaction,which is attributed to its weak hydrogen adsorption *** this study,we controlled the chemical state of Ni using plasma vapor deposition(PVD)followed by heat treatment,selective Al leaching,and electrochemical reduction.X-ray diffraction(XRD),scanning microscopy(SEM),transmission electron microscopy(TEM),and energy-dispersive X-ray spectroscopy(EDS)were used to confirm the phase evolution of the electrocatalysts during *** reveal that the heat-treated Ni-Al alloy with a thick Ni2Al3surface layer underwent selective Al leaching and produced biphasic interfaces comprising Ni(OH)_(2) and NiAl IMCs at the edges of the grains in the outermost surface *** oxidation of the interfacing NiAl IMCs facilitated the partial reduction of Ni(OH)_(2) to Ni(OH)_(2)/Ni in the grains during electrochemical reduction,as confirmed by X-ray photoelectron spectroscopy(XPS).An electrocatalyst containing partially reduced Ni(OH)_(2)/Ni exhibited an overpotential of 54 mV at 10 mA/cm^(2) in a half-cell measurement,and a cell voltage of 1.675 V at 0.4 A/cm2for single-cell operation.A combined experimental and theoretical study(density functional theory calculations)revealed that the superior HER activity was attributed to the presence of partially reduced metallic Ni with various defects and residual Al,which facilitated water adsorption,dissociation,and finally hydrogen evolution.

关键词： Raney nickel HERChemical leaching Intrinsic activity partial reduction

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Tf_2O-TMDS combination for the direct reductive transformation of secondary amides to aldimines,aldehydes, and/or amines

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Science China Chemistry 2016年第12期59卷 1638-1644页

作者： Qi-Wei Lang Xiu-Ning Hu Pei-Qiang Huang Department of Chemistry Fujian Provincial Key Laboratory of Chemical Biology Collaborative Innovation Center of Chemistry for Energy Materials College of Chemistry and Chemical Engineering Xiamen University

The direct partial reduction of highly stable secondary amides to more reactive aldimines and aldehydes is a challenging yet highly demanding transformation. In this context, only three methods have been reported. We report herein an improved version of the Charette's method. Our protocol consists of activation of secondary amides with triflic anhydride/2-fluoropyridine,and partial reduction of the resulting intermediates with 1,1,3,3-tetramethyldisiloxane(TMDS), which delivered aldimines or aldehydes upon acidic hydrolysis. Aromatic amides were reduced to the corresponding aldimines in 85%–100% NMR yields,and yields(NMR) from aliphatic amides were 72%–86%. Acidic hydrolysis of the aldimine intermediates afforded, in one-pot,the corresponding aldehydes in 80%–96% yields. A simple protocol was established to isolate labile aldimines in pure form in92%–96% yields. The improved method gave generally higher yields as compared to the known ones, and features the use of cheaper and more atom-economical TMDS as a chemoselective reducing agent. In addition, a convenient extraction protocol has been established to allow the isolation of amines, which constitutes a mild method for the N-deacylation of amides, another highly desirable transformation. The extended method retains the advantages of the original method of Charette in terms of mild conditions, good functional group tolerance, and excellent chemoselectivity.

关键词： secondary amides amide activation partial reduction aldimines N-deacylation

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