AACVD-fabricated Zn-modified WO3 photoanodes for enhanced solar water oxidation

Abstract

The photoelectrochemical (PEC) performance of WO₃ photoanodes is limited by poor charge transport and high recombination losses. In this work, Zn-modified WO₃ thin films (0, 2, 10, and 20 wt%) were fabricated via a two-step aerosol-assisted chemical vapour deposition (AACVD) method to investigate the effect of Zn incorporation on material properties and PEC water oxidation performance. The 10 wt% Zn–WO₃ film exhibited the highest photocurrent density (0.68 mA cm⁻² at 1.23 V_RHE under 1-sun illumination), corresponding to an enhancement of over 70% compared to pristine WO₃. This improvement is associated with nanorod morphology, enhanced (002) preferred orientation, bandgap narrowing (2.50 eV), and increased donor density, which promote more efficient charge transport and interfacial charge transfer. Electrochemical impedance and Mott–Schottky analyses further confirm reduced interfacial resistance and increased carrier density for the optimised composition. These results demonstrate that Zn doping improves the PEC water oxidation performance of WO₃ photoanodes.