Fu Huai Qin, Zhou Min, Liu Peng Fei, Liu Porun, Yin Huajie, Sun Kai Zhi, Yang Hua Gui, Al-Mamun Mohammad, Hu Peijun, Wang Hai-Feng, Zhao Huijun
Centre for Catalysis and Clean Energy, Gold Coast Campus, Griffith University, Gold Coast, QLD 4222, Australia.
Key Laboratory for Advanced Materials, Centre for Computational Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China.
J Am Chem Soc. 2022 Apr 6;144(13):6028-6039. doi: 10.1021/jacs.2c01094. Epub 2022 Mar 18.
Water-alkaline electrolysis holds a great promise for industry-scale hydrogen production but is hindered by the lack of enabling hydrogen evolution reaction electrocatalysts to operate at ampere-level current densities under low overpotentials. Here, we report the use of hydrogen spillover-bridged water dissociation/hydrogen formation processes occurring at the synergistically hybridized NiS/CrS sites to incapacitate the inhibition effect of high-current-density-induced high hydrogen coverage at the water dissociation site and concurrently promote Volmer/Tafel processes. The mechanistic insights critically important to enable ampere-level current density operation are depicted from the experimental and theoretical studies. The Volmer process is drastically boosted by the strong HO adsorption at Cr sites of CrS, the efficient HO* dissociation a heterolytic cleavage process (Cr-HO* + S(#) → Cr-OH* + S-H) on the Cr/S sites in CrS, and the rapid desorption of OH* from Cr sites of CrS a new water-assisted desorption mechanism (Cr-OH* + HO(aq) → Cr-HO* + OH(aq)), while the efficient Tafel process is achieved through hydrogen spillover to rapidly transfer H from the synergistically located H-rich site (CrS) to the H-deficient site (NiS) with excellent hydrogen formation activity. As a result, the hybridized NiS/CrS electrocatalyst can readily achieve a current density of 3.5 A cm under an overpotential of 251 ± 3 mV in 1.0 M KOH electrolyte. The concept exemplified in this work provides a useful means to address the shortfalls of ampere-level current-density-tolerant Hydrogen evolution reaction (HER) electrocatalysts.
水电解制氢在工业规模制氢方面具有巨大潜力，但由于缺乏能够在低过电位下以安培级电流密度运行的析氢反应电催化剂而受到阻碍。在此，我们报道了利用在协同杂化的NiS/CrS位点发生的氢溢流桥接水离解/氢形成过程，以消除高电流密度引起的高氢覆盖在水离解位点的抑制作用，并同时促进Volmer/Tafel过程。从实验和理论研究中阐述了对于实现安培级电流密度运行至关重要的机理见解。Volmer过程通过CrS的Cr位点上强烈的HO吸附、CrS中Cr/S位点上高效的HO离解（一种异裂过程（Cr-HO + S(#) → Cr-OH* + S-H））以及CrS的Cr位点上OH的快速脱附（一种新的水辅助脱附机制（Cr-OH + HO(aq) → Cr-HO* + OH(aq)））而得到极大促进，而高效的Tafel过程则通过氢溢流实现，即将H从协同定位的富氢位点（CrS）快速转移到具有优异氢形成活性的贫氢位点（NiS）。结果，在1.0 M KOH电解液中，杂化的NiS/CrS电催化剂在251 ± 3 mV的过电位下能够轻松实现3.5 A cm的电流密度。这项工作中所例证的概念为解决耐安培级电流密度的析氢反应（HER）电催化剂的不足提供了一种有用的方法。
