Exploring the Heterostructure Engineering of SnS/NiCo₂O₄for Overall Water Splitting

A bifunctional electrocatalyst with a low overpotential is a prerequisite for realizing efficient overall water splitting. In this scenario, the search for low-cost and non-precious electrocatalysts in electrolysis research leads to the employment of spinel oxides and chalcogenides. Herein, a heterostructure bifunctional electrocatalyst consisting of tin sulfide (SnS) nanosheets engrafted onto nickel cobalt oxide (NiCo₂O₄) nanoneedles suspended on nickel foam was prepared using the conventional hydrothermal method. The interface of SnS/NiCo₂O₄was found to contain half-metallic Sn-O bonds as evident from density functional theory calculations and X-ray photoelectron spectroscopy. Furthermore, SnS growth on NiCo₂O₄triggers new crystalline (0 2 1) planes and the vertical orientation of nanosheets enhancing the catalytic kinetics by exposing more surface S atoms, which provide a lower adsorption energy for hydrogen/oxygen moieties. The SnS/NiCo₂O₄catalyst on Ni foam exhibits overpotentials of 302 mV (at a current density of 20 mA cm^-2) and 154 mV (at a current density of 20 mA cm^-2) for oxygen and hydrogen evolution reactions, respectively, in a 1.0 M potassium hydroxide electrolyte. Furthermore, a potential of 1.57 V was required to attain a current density of 10 mA cm^-2in the overall water-splitting process. Apart from this bifunctional ability, the catalyst shows good stability (>25 h) in the electrolyte. The growth of chalcogenides on spinel oxides paves a new way to realize efficient electrocatalysts with reduced adsorption energies.