Insight into the boosted activity of TiO2–CoP composites for hydrogen evolution reaction: Accelerated mass transfer, optimized interfacial water, and promoted intrinsic activity

Abstract

The use of abundant elements in the earth as electrocatalytic hydrogen production catalysts is of great significance for hydrogen energy cycling. Herein, we report amorphous TiO2-decorated CoP/NF (TiO2–CoP/NF) as an excellent electrocatalyst for alkaline hydrogen evolution reaction (HER). The well-dispersed amorphous TiO2 on nanoneedle-like CoP arrays preserves the crystal structure of CoP and changes its electronic structure by interfacial charge transfer. Compared to CoP/NF catalyst, the TiO2–CoP/NF composite catalyst exhibits high HER activity with an overpotential of 61 mV at 10 mA cm−2 and high stability. Importantly, it almost maintains the Volmer step as a rate-determining step (RDS) and the Tafel slope at a wide cathodic potential range showing the fast kinetics under large polarization regions. Theoretical simulations reveal that the combination of TiO2 and CoP selectively accelerates the hydrated K+ diffusion, regulates the interfacial water orientation to adapt to the subsequent smooth water dissociation, and optimizes *H adsorption/H2 desorption. The strengthened coupling of HER multi-scale-processes on transition metal compound composites catalysts is the underlying mechanism for improving HER activity.