Constructing collaborative interface between Mo2N and NiS as efficient bifunctional electrocatalysts for overall water splitting

Abstract

Solar-driven electrocatalytic water splitting is a promising technology to produce renewable hydrogen fuel. To accomplish this perspective, it is urgent to exploit high-efficiency and robust bifunctional electrocatalysts. Herein, a hybrid Mo2N/NiS heterojunction with synergistic effect is developed as bifunctional electrocatalyst for high-efficiency water splitting in alkaline media. Through high-temperature calcination and in-situ hydrothermal growth process, NiS nanocrystals are successfully anchored on porous Mo2N to produce a well-defined heterointerface by forming MoS bonds. The optimized Mo2N/NiS hybrids exhibit a much-enhanced electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) than that of individual Mo2N and NiS in 1.0 M KOH. Moreover, benefitting from the robust chemical stability of Mo2N substrate, Mo2N/NiS hybrids presents an excellent long-term durability. The density functional theory calculations reveal that the improved HER and OER activities are primarily enabled by the synergistic effect of interface between Mo2N and NiS, NiS accelerates the water dissociation while Mo2N optimize the intermediates adsorption. When the as-prepared Mo2N/NiS heterojunction is used as bifunctional catalysts in a photovoltaic water splitting system, it exhibits a favorable solar-to-hydrogen energy conversion efficiency of 8.4 %, which is superior to some of reported noble-metal based catalysts. This work provides a facile and efficient strategy to design and fabricate the bifunctional catalysts for water splitting.