Improved Photoelectrochemical Water Splitting of CaNbO2N Photoanodes by Co-Pi Photodeposition and Surface Passivation

TL;DR

This study enhances CaNbO2N photoanodes for solar water splitting by optimizing preparation methods and surface modifications, achieving higher photocurrent through Co-Pi deposition and Al2O3 passivation.

Contribution

It introduces a new preparation method for CaNbO2N particles and demonstrates improved photoelectrochemical performance via surface passivation and co-catalyst deposition.

Findings

Achieved a photocurrent density of 70 μA/cm² at 1.23 V vs RHE.

Enhanced photoactivity due to surface area and light absorption improvements.

Surface modifications significantly improved oxygen evolution kinetics.

Abstract

Photoelectrochemical solar water splitting is a promising approach to convert solar energy into sustainable hydrogen fuel using semiconductor electrodes. Due to their visible light absorption properties, oxynitrides have shown to be attractive photocatalysts for this application. In this study, the influence of the preparation method of CaNbO2N particles on their morphological and optical properties, and thereby their photoelectrochemical performance, is investigated. The best performing CaNbO2N photoanode is produced by ammonolysis of Nb enriched calcium niobium oxide. The enhanced photoactivity arises from an enlarged surface area and superior visible light absorption properties. The photoactivity of this photoanode was further enhanced by photodeposition of Co-Pi co-catalyst and by atomic layer deposition of an Al2O3 overlayer. A photocurrent density of 70 microA.cm-2 at 1.23 V vs RHE was achieved. The observed enhancement of the photoelectrochemical performance after Co-Pi/Al2O3 deposition is the combined effect of the improved kinetics of oxygen evolution due to the Co-Pi co-catalyst and the reduced surface recombination of the photogenerated carriers at the Al2O3 surface layer.