通过温和的镍腐蚀制备珊瑚状FeNi(OH)x/Ni作为一种一体化高效水分解电极

高效稳定并可同时催化析氧反应(OER)和析氢反应(HER)的非贵金属催化剂对于实现廉价水分解电解槽的商业化十分重要.虽然众多研究表明FeNi(OH)x是一种极具潜力的催化剂,但是在基础研究与更有实用前景的电极之间仍有许多空白亟待填补.比如,基础研究多基于薄膜电极,其催化剂内部导电性的影响通常可以忽略.而基于实用化的电极则需要负载较厚的催化剂膜以获得更多的活性位,与此同时,其催化剂内部导电性的不利影响将会增大.此外,物质传递方面也会出现类似的情况.因此,一些在基础研究中显示出高本征活性的催化剂,在更加接近实际应用的体系下难以表现出预期的高活性.对于这一问题,目前鲜有相关的研究报道.基于上述分析,本文报道了一种经济且环保的方法,以制备珊瑚状的FeNi(OH)x/Ni催化剂.在碱性条件下,该催化剂具有同时催化OER和HER,从而实现全水分解的能力.在催化剂的制备过程中,具有高本征活性的FeNi(OH)x纳米片借助Fe(NO3)3对Ni温和的腐蚀过程,被原位负载到珊瑚状镍骨架上.这些纳米片与电沉积制备的珊瑚镍骨架以及3D泡沫镍基底一起构成了一体化的析气电极.这样的电极结构有助于暴露活性位、电解质快速传递和气体产物的迅速释放.此外,与珊瑚状金属镍骨架的复合也有利于减轻较厚的催化剂薄膜所带来的导电性降低的负面影响.在1.0mol L-1 KOH溶液中,以FeNi(OH)x/Ni同时作为阳极和阴极而构建的对称电解槽表现出了优异的催化活性,只需要施加1.52 V的槽压即获得10 mA cm-2的催化电流密度.其活性甚至优于当前最佳的由贵金属催化剂RuO2和Pt/C构建的非对称电解槽所表现出来的活性(10 mA cm-2的槽压为1.55 V).本文提供了一种简便易行且十分可靠的制备更加实用、具有潜力且可负担的水分解装置的策略.

Hierarchical coral-like FeNi(OH)x/Ni via mild corrosion of nickel as an integrated electrode for efficient overall water splitting

Efficient, stable, and noble-metal-free electrocatalysts for both the oxygen evolution reaction and the hydrogen evolution reaction are highly imperative for the realization of low-cost commercial water-splitting electrolyzers. Herein, a cost-effective and ecofriendly strategy is reported to fabricate coral-like FeNi(OH)_x/Ni as a bifunctional electrocatalyst for overall water splitting in alkaline media. With the assistance of mild corrosion of Ni by Fe(NO₃)₃, in situ generated FeNi(OH)_x nanosheets are intimately attached on metallic coral-like Ni. Integration of these nanosheets with the electrodeposited coral-like Ni skeleton and the supermacroporous Ni foam substrate forms a binder-free hierarchical electrode, which is beneficial for exposing catalytic active sites, accelerating mass transport, and facilitating the release of gaseous species. In 1.0 mol L^?1 KOH solution, a symmetric electrolyzer constructed with FeNi(OH)_x/Ni as both the anode and the cathode exhibits an excellent activity with an applied potential difference of 1.52 V at 10 mA cm^?2, which is superior to that of an asymmetric electrolyzer constructed with the state-of-the-art RuO₂-PtC couple (applied potential difference of 1.55 V at 10 mA cm^?2). This work contributes a facile and reliable strategy for manufacturing affordable, practical, and promising water-splitting devices.