In Situ Synthesis of Copper Sulfide‐Nickel Sulfide Arrays on Three‐Dimensional Nickel Foam for Overall Water Splitting

Abstract Developing simple and cost‐effective bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an effective strategy to curb the current energy demands. Herein, we report the hydrothermal synthesis of copper sulfide‐nickel sulfide (Cu 2 S‐Ni 3 S 2 ) arrays supported by three‐dimensional conducting nickel foam as a substrate (Cu 2 S‐Ni 3 S 2 /NF). Cu 2 S‐Ni 3 S 2 /NF demonstrates prominent electrocatalytic activity and persistent stability (>25 h) in alkaline solution (1 M KOH), requiring the overpotential of −149 mV and 329 mV to drive the catalytic current density of 10 mA cm −2 for the HER and OER, respectively. Furthermore, overall‐water splitting in symmetrical configurations required the cell‐voltage of 1.77 V to deliver 10 mA cm −2 , complimented with an ultra‐long term stability for 100 h. Therefore Cu 2 S‐Ni 3 S 2 /NF could be a promising and effective electrocatalyst for water‐splitting reactions.