Rational design of bifunctional hydroxide/sulfide heterostructured catalyst for efficient electrochemical seawater splitting

Heterostructure engineering is one of the most promising strategies for efficient water splitting by electro-catalysts. However, it remains challenging to design heterostructured catalysts to achieve the desired goals in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater splitting. Here, par-ticulate heterostructures of FeCoNi hydroxide/sulfide supported on nickel foams were prepared by hydrothermal methods to achieve a high-performance bifunctional catalyst. The synthesized FeCoNi hydroxide/sulfide exhibited excellent electrocatalytic performance, requiring an overpotential of 195 mV for OER and 76 mV for HER to achieve a current density of 10 mA cm-2 while showing excellent stability. The catalyst maintains its excellent performance even in artificial or natural seawater with high salinity, which is a harsh environment. When applied directly to a water splitting system, the catalyst achieves a current density of 10 mA cm-2 at only 1.5 V (1.57 V in alkaline seawater). The FeCoNi hydroxide/sulfide heterostructure is an excellent electrocatalytic bifunctional catalyst due to compositional modulation, systematic charge transfer optimization, improved in-termediates adsorption, and increased electrocatalytic active sites and the synergistic effect of the heterostructure.