Built-in electric field in bifunctional electrocatalyst (Ni3S2@Ni9S8) for high-efficiency OER and overall water splitting performance

It is a giant challenge to fabrication inexpensive and efficient bifunctional electrocatalyst to replacing precious metal material in water splitting field. Herein, based on built-in electric field, adsorption intermediates and d-band center theories, Mo and Fe co-engineered Ni3S2@Ni9S8 hierarchical coupling interface is designed. The optimized hierarchical nanorods array facilitate full contact between electrolyte and surface of the catalyst, increasing the number of electrocatalytic sites. Characterizations indicated the successful introduction of Mo and Fe into Ni3S2@Ni9S8 increasing the number of active sites as well as fabricated a unique Ni3S2@Ni9S8 core-shell coupling interface and formed built-in electric field, improving the intrinsic conductivity of the catalyst. The theoretical calculation showing the introduction of Fe and Mo modulate the adsorption energy of the electrocatalyst for the water splitting intermediates, elevating d-band center, so Ni3S2@Ni9S8 catalyst shows excellent electrochemical performance. Specifically, the low overpo tentials of 167 mV is procured at the current density of 10 mA cm−2 for OER in 1 M KOH. Importantly, as a bifunctional electrocatalyst, Ni3S2@Ni9S8 exhibit excellent catalytic activity at a low voltage of 1.62 V to reach a current density of 10 mA cm−2 for 24 h overall water splitting in alkaline condition. These studies provide a feasible and promising strategy for the preparation of inexpensive electrocatalysts and offers more possibilities for further exploration of electrocatalysis in the energy conversion field.