Science China Materials | 2019
A multiphase nickel iron sulfide hybrid electrode for highly active oxygen evolution
Abstract
Development of highly active electrocatalysts for oxygen evolution reaction (OER) is one of the critical issues for water splitting, and most reported catalysts operate at overpotentials above 190 mV. Here we present a multiphase nickel iron sulfide (MPS) hybrid electrode with a hierarchical structure of iron doped NiS and Ni 3 S 2 , possessing a benchmark OER activity in alkaline media with a potential as low as 1.33 V (vs. reversible hydrogen electrode) to drive an OER current density of 10 mA cm −2 . The Fe doped NiS, combined with highly conductive disulfide phase on porous Ni foam, is believed to be responsible for the ultrahigh activity. Further more, density functional theory simulation reveals that partially oxidized sulfur sites in Fe doped NiS could dramatically lower the energy barrier for the rate determining elementary reaction, thus contributing to the active oxygen evolution. 开发高效和低成本的析氧电极材料是工业电解水制氢技术发展道路上至关重要的技术难题. 本文利用溶剂热方法将镍铁水滑石阵列转化为具有铁掺杂的多相硫化镍(NiS和Ni 3 S 2 )阵列, 制备出一种具有高效析氧性能的电极材料. 粗糙的纳米片表面有利于高活性位点的暴露. 电化学分析表明其仅需要100 mV的过电位就可以达到10 mA cm −2 的电流密度, 相对于镍铁水滑石阵列降低了130 mV. 我们进一步通过密度泛函理论计算来揭示其活性提升机理, 发现具有部分S氧化的Fe掺杂NiS可以极大地降低析氧反应中间体形成的阻力, 从而加快催化反应进行, 提高催化活性. 另一方面, (Ni,Fe)S和(Ni,Fe) 3 S 2 与三维多孔泡沫镍结构有很好的结合作用, 反应电子可以通过金属性的二硫化镍相进行高效传输, 进一步加速析氧催化进程.