Design of noble metal free hierarchical VS2 onto WO3 nanoflakes as an effective heterojunction strategy for enhanced photoelectrochemical water oxidation

Abstract

WO₃ is a promising photoanodic material for photoelectrochemical oxygen evolution. However, its use is limited due to its slower surface reaction kinetics leading to undesired carrier recombination. Herein, we propose the design of highly surface reactive and noble metal free VS₂ nanoflowers onto an in situ grown WO₃ photoanode as a heterojunction strategy for efficient charge separation. VS₂, a promising transition metal-based material with active sites both on the edge and basal planes, reduces the surface charge recombination and enhances the kinetics of the O₂ evolution reaction at the photoanode and electrolyte interface. A significant increment in photocurrent density is observed for the WO₃–VS₂ composite compared to the bare WO₃ with an increase in charge carrier density from 2.5 × 10²¹ for WO₃ to 1.5 × 10²² cm³ for WO₃–VS₂. Electrochemical impedance spectroscopy indicates an effective reduction in charge transfer resistance from 7.71 × 10⁵ for WO₃ to 2.79 × 10³ Ω for WO₃–VS₂. A faradaic efficiency of 87% is indicative that the oxygen generated in the reaction is mainly due to the photoelectrochemical water oxidation.