Abstract: Water electrolysis in alkaline media for hydrogen production is regarded as one of the most effective approaches to address the energy crisis and environmental pollution associated with fossil fuels, and the development of non-noble metal catalysts with low cost and high activity is one of the key factors for realizing its industrial large-scale application. Ni is a promising candidate for the electrocatalytic hydrogen evolution reaction, due to its high intrinsic catalytic activity and stability, and good corrosion resistance. However, the overall hydrogen evolution rate on pure Ni is limited by the hydrogen desorption step. Alloying Ni with another metal to transform the electronic structure, is an effective strategy to enhance its electrocatalytic activity. Herein, Mg is proposed as the alloy element for Ni to form Mg-Ni catalyst. In this work, using nickel foam (NF) as the substrate material, Mg-Ni alloy films were in?situ grown on NF via potentiostatic electrolysis in molten NaCl-KCl-MgCl2, and self-supporting Mg-Ni/NF electrodes were successfully fabricated, which can be directly used for catalytic hydrogen evolution. The phase structure, surface morphology, element distribution, and chemical state of the alloy on NF were analyzed by X-ray diffraction (XRD), electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity and stability of the as-fabricated electrode were then examined in 1.0 mol/L KOH solution. The Mg-Ni/NF-8 h electrode was highly effective for hydrogen evolution reaction with a low overpotential of only 49.5 mV to deliver a current density of 10 mA/cm2 and a small Tafel slope of 36.0 mV/dec, exceeding the noble Pt catalyst. The electrode maintained a long-term stable electrolysis of 106 h at a high current density of 100 mA/cm2. The phase composition, microstructure, and surface characteristics of the electrode were unchanged after long-term electrolysis, indicating superior electrochemical stability with no obvious activity decay. The Mg2Ni/MgNi2 heterostructure, huge specific surface area originating from nanosheets, and stable self-supported structure were the main reasons for the electrode to achieve excellent electrochemical activity and stability. This work offers new insights into the designing of efficient and stable non-precious metal hydrogen evolution materials, expanding the application of magnesium in the field of catalysis.

Key words: hydrogen evolution reaction, molten salt electrodeposition, Mg-Ni/NF electrode, water electrolysis

摘要： 开发高效稳定的非贵金属析氢催化剂，对推动碱性电解水制氢技术工业化应用具有重要意义。本工作以泡沫镍(NF)为基底材料，通过熔盐电沉积法在其表面原位生长Mg-Ni合金，制得了可直接用于催化析氢反应的自支撑型Mg-Ni/NF电极。利用X射线衍射、扫描电镜-EDS与X光电子能谱分析了Mg-Ni/NF电极的物相结构、微观形貌和表面元素状态，并采用电化学工作站测定了电极的电催化析氢活性和稳定性。结果表明，电极表面主要为双相Mg2Ni/MgNi2异质结构，呈纳米片状结构相互连接，形成了微纳米级网孔。在1.0 mol/L KOH溶液中，Mg-Ni/NF-8 h电极在10 mA/cm2电流密度下的析氢过电位仅为49.5 mV，Tafel斜率为36.0 mV/dec；100 mA/cm2电流密度下持续电解106 h后仍然具有良好的催化活性。本研究为制备高性能非贵金属析氢材料、拓展镁在催化领域的应用提供了新思路。

关键词: 析氢反应, 熔盐电沉积, Mg-Ni/NF电极, 电解水