Constructing ZnCoFe@NiS/NF Micro-flower Structure as Highly Efficient Electrocatalysts for Overall Water Splitting

The development of efficient and stable bifunctional electrocatalysts composed of Earth-abundant elements to facilitate both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in water splitting still presents considerable challenges. In this work, a ZnCoFe@NiS/NF catalyst featuring a three-dimensional spherical micro-flower structure supported on nickel foam was successfully prepared through a simple, multi-step hydrothermal synthesis method. Owing to its significantly enhanced specific surface area, abundance of active sites, and superior electron conductivity, the ZnCoFe@NiS/NF catalyst demonstrates outstanding bifunctional catalytic performance in 1 M KOH. At a current density of 10 mA cm − 2 , the overpotential is as low as 170 mV for the OER and 178 mV for the HER. Specifically, an overall water splitting electrolyzer constructed from ZnCoFe@NiS/NF requires only a remarkably low operating voltage of 1.52 V to achieve a current density of 10 mA cm − 2 , surpassing the performance of the majority of reported bifunctional metal sulfide electrocatalysts. Furthermore, the catalyst operates at a similarly low voltage of 1.72 V and maintains stability for more than 100 h at a current density of 50 mA cm − 2 . This work not only reveals the critical importance of controlling morphology and electronic properties for enhancing the kinetics of electrocatalytic reactions, but also offers a simple and effective synthetic route for the large-scale production of high-performance and highly stable overall water splitting electrocatalysts. Graphical