Crossed NiCo 2 S 4 Nanowires Supported on Nickel Foam as a Bifunctional Catalyst for Efficient Overall Water Splitting

Abstract Increasing demands for renewable clean fuel and environmental protection have attracted much research on energy production and conversion. Designing efficient and stable electrocatalysts, which has been recognized as one of the primary goals for anodic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), provides the most prospective route towards mass production of hydrogen from renewable sources. In this paper, 3D‐networked, ultrathin, and crossed nanowires NiCo 2 S 4 grown on Ni foam (NF) was successfully synthesized by a simple hydrothermal method and worked as a unprecious metal‐based overall water splitting electrocatalyst. NiCo 2 S 4 /NF possess predominant catalytic activity with an overpotential of 251 mV to drive a current density of 40 mA cm −2 in alkaline media and 191 mV at 10 mA cm −2 for HER in 1.0 M KOH electrolyte. Moreover, NiCo 2 S 4 /NF||NiCo 2 S 4 /NF was constructed by employing NiCo 2 S 4 /NF as both the cathode and anode, the overall water splitting electrolyzer results revealed that only 1.59 V was required to reach the current density of 10 mA cm −2 . Notably, NiCo 2 S 4 /NF ||NiCo 2 S 4 /NF also shows long‐term electrochemical durability with its activity being retained for over 12 h‐long. The newly developed cost‐effective high efficent electrocatalyst towards water splitting provides a novel approach for the design of earth‐abundant transition metal sulfide for high efficiency overall water splitting electrode.