ZnO/BiOI heterojunction photoanodes with enhanced photoelectrochemical water oxidation activity

ZnO/BiOI heterojunction photoanode thin films were prepared by aerosol-assisted chemical vapour deposition, and the impact of growth temperature and film thickness on the water oxidation functionality was systematically investigated. A top ZnO layer with a thickness of 120 nm (deposited at 350 degrees C) and a 390 nm thick BiOI layer (deposited at 300 degrees C) were found to achieve the best photoelectrochemical performance of the heterojunction. The ZnO/BiOI heterojunction exhibited a significant increase in photoelectrochemical activity, with a photo-current of 0.27 mA center dot cm(-2) observed at 1.1 VRHE (350 nm, 2.58 mW center dot cm(-2)), which is similar to 2.2 times higher than that of single-layer ZnO and far higher than that of BiOI. Photoluminescence spectroscopy and transient absorption spectroscopy measurements showed that there was effective charge transfer across the heterojunction which spatially separated charge carriers and increased their lifetime and ability to drive photoelectrochemical water oxidation.

Automated summary

ZnO/BiOI heterojunction photoanode thin films were investigated for their water oxidation functionality, and it was found that a ZnO layer with a thickness of 120 nm (deposited at 350 degrees C) and a BiOI layer with a thickness of 390 nm (deposited at 300 degrees C) achieved the best photoelectrochemical performance. The heterojunction showed a significant increase in photoelectrochemical activity, with a photo-current of 0.27 mA·cm-2 observed at 1.1 VRHE, which is about 2.2 times higher than that of single-layer ZnO and much higher than that of BiOI. Analysis revealed effective charge transfer and spatial separation of charge carriers at the heterojunction, leading to improved lifetime and ability to drive photoelectrochemical water oxidation.