Ex situ flame vapor-doped oxophilic metals on WP/WOx nanowires for enhanced alkaline hydrogen evolution activity

Abstract

Developing effective non-noble hydrogen evolution reaction (HER) electrocatalysts in alkaline electrolyte is desirable for efficient water splitting, but it is challenging. In this work, various oxophilic metals (Co, Cu, Mn, and Cr) were incorporated into WP/WOx films as water dissociation promotors to enhance the HER activity. Flame vapor deposition (FVD) was used for ex situ facile doping of metals on WP/WOx. The prepared metal-doped WP/WOx catalysts exhibited improved HER activities in alkaline solution, resulted from promoted water dissociation step by oxophilic doping metals on WP/WOx. Specifically, Co-doped WP/WOx (Co:WP/WO) film showed the highest intrinsic activity of HER among metal dopants owing to an optimum oxophilicity of Co. Nanostructure engineering was employed to further enhance the HER performance of the Co:WP/WO catalysts. A nanowires (NWs) array of WP/WO was fabricated by thermal evaporation, providing numerous active sites and faster pathways for mass transport and charge transfer. With the synergistic effect of Co dopants and the NWs structure, the Co:WP/WO NWs catalyst exhibited a superior HER performance in alkaline media with an overpotential of 104 mV at a current density of 10 mA cm−2 and stability of over 50 h in 1.0 M KOH solution. Lastly, combining our Co:WP/WO NW – Ir/NF (HER – OER catalysts) with tandem perovskite solar cell demonstrates unassisted solar hydrogen generation by photovoltaic electrochemical (PV-EC) system, generating a solar to hydrogen (STH) efficiency of 10.2 %. Our study provides a rational strategy for developing efficient non-noble HER electrocatalysts that are highly active in alkaline media.