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

Amorphous TiO 2 -decorated CoP/NF composite catalyst exhibits high HER activity showing fast kinetics at a wild cathodic polarization range. Theoretical simulations confirm that the combination of TiO 2 and CoP can boost the HER activity by selectively accelerating the hydrated cation diffusion, regulating the interfacial water orientation, facilitating water dissociation, and optimizing *H adsorption/H 2 desorption. 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 TiO 2 -decorated CoP/NF (TiO 2 –CoP/NF) as an excellent electrocatalyst for alkaline hydrogen evolution reaction (HER). The well-dispersed amorphous TiO 2 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 TiO 2 –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 TiO 2 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/H 2 desorption. The strengthened coupling of HER multi-scale-processes on transition metal compound composites catalysts is the underlying mechanism for improving HER activity.