A nanostructured chromium(iii) oxide/tungsten(vi) oxide p–n junction photoanode toward enhanced efficiency for water oxidation

Abstract

A nanostructured chromium(III) oxide/tungsten(VI) oxide (Cr₂O₃/WO₃) p–n junction photoanode is established here. It is prepared by depositing Cr₂O₃ nanoparticles onto WO₃ nanosheet arrays. The formation of a p–n junction is confirmed by the Mott–Schottky plot and photocurrent measurements. Electrochemical and spectroscopic methods indicate that the recombination rate of photogenerated charges becomes lower in this photoanode. Consequently, its onset potential shifts negatively by about 0.1 V and photocurrent density increases from 0.7 to 1.8 mA cm⁻² at 1.8 V vs. RHE. The incident photon-to-current efficiency (IPCE) also shows a one-fold improvement. In addition, the construction of the p–n junction leads to an increase of faradaic efficiency (holes to oxygen) from 73.9% to 92.0%, which is attributed to the suppression of side reactions in water oxidation. This work will provide new inspiration for improving the performance of WO₃ and other photoanodes.