High‐Performance Bifunctional Ni−Fe−S Catalyst in situ Synthesized within Graphite Intergranular Nanopores for Overall Water Splitting
Xiaofan Yang, Jing Li, Xinming Yang, Chao‐Xiong Li, Fang Li, Bing Li, Jianbo He
Abstract
Abstract Low‐cost and efficient bifunctional catalysts are urgently needed for overall water splitting used in large‐scale energy storage. In this study, we develop a nickel and iron (di)sulfide (Ni−Fe−S) composite catalyst that is in situ synthesized and fixed within the intergranular nanopores inside high pure polycrystalline graphite. Two precursor solutions (reactants) may permeate the graphite intergranular pores to a depth of more than 3.5 mm. The nanoscale pores serve as an array of nanoreactors for the synthesis of the Ni−Fe−S nanoparticles under conditions much milder than usual. The prepared catalyst efficiently catalyzes both the hydrogen and oxygen evolution reactions (HER and OER) in 1.0 M KOH. It delivers a current density of 400 mA cm −2 at a full cell voltage of around 2.3 V without considerable activity decay over 24 h electrolysis. The active species of the catalyst are different for the HER and OER and discussed accordingly. The synthesis strategy based on the nanopores in a monolithic conductive substrate proves to be a simple, efficient, and promising way to prepare electrocatalysts that are cheap, abundant, and industrially attractive.