Synergistically coupling of Ni–Fe LDH arrays with hollow Co–Mo sulfide nanotriangles for highly efficient overall water splitting

Abstract Developing bifunctional catalysts that can catalyze both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is pivotal to commercializing large‐scale water splitting. Herein, a novel hollow nanotriangle composed of NiFe LDH‐CoMoS x heterojunction (H‐CMS x @NiFe LDH) is proposed as a highly efficient bifunctional electrocatalyst for both OER and HER. To fabricate a heterojunction system, ultra‐thin nickel–iron layered double hydroxide (NiFe LDH) nanosheets are uniformly electrodeposited onto a metal–organic framework‐derived hollow CoMoS x nanotriangle. The strong coupling of CoMoS x and NiFe LDH catalysts forms the intimate heterojunction interfaces to facilitate interfacial charge transfer, which is favorable to enhance the bifunctional catalytic activity. Moreover, the large void of CoMoS x nanotriangles and interconnected ultra‐thin NiFe LDH nanosheets result in good electrolyte penetration and gas release. Therefore, the as‐prepared H‐CMS x @NiFe LDH on nickel foam (NF) exhibits an impressive catalytic activity and durability for OER and HER activities, delivering a current density of 100 mA·cm −2 at the small overpotentials of 214 and 299 mV in OER and HER, respectively. Meanwhile, H‐CMS x @NiFe LDH/NF proves to be an effective electrode for an alkaline electrolyzer, as a voltage of only 1.99 V is enough to achieve a current density voltage of only 1.99 V is enough to achieve a current density of 400 mA·cm −2 with no degradation in performance over 50 h.