Multi-dimensional composite catalyst NiFeCoMoS/NFF for overall electrochemical water splitting†

Abstract

Precise catalyst design is essential in the electrolysis of water to deliver clean energy, where the challenge is to construct highly active sites at the electrocatalyst interface. In this study, CoPVP/NFF (NiFe foam) and Mo–CoPVP/NFF precursors were synthesized sequentially in a hydrothermal procedure using NiFe foam as substrate with the ultimate formation of a NiFeCoMoS/NFF electrocatalyst by vulcanization at 350°. The NiFeCoMoS/NFF system exhibits a complex 1D–2D–3D composite structure with 1D nanoparticles attached to a 2D nano-paper on the surface of the 3D NiFe foam. The overpotentials associated with hydrogen and oxygen evolution by NiFeCoMoS/NFF are 123 mV and 245 mV, respectively, at a current density of 10 mA cm⁻². A three-electrode system using NiFeCoMoS/NFF as working and counter electrode has been assembled that can generate current densities of 100 mA cm⁻² at voltages of 1.87 V. Theoretical (DFT) calculations have shown that NiFeCoMoS/NFF exhibits favorable H adsorption energetics and a low OER reaction barrier. This study has identified a viable means of enhancing the efficiency of water electrolysis by regulating catalyst surface structure.