Interface engineering with an AlOx dielectric layer enabling an ultrastable Ta3N5 photoanode for photoelectrochemical water oxidation

Abstract

Photoelectrochemical water splitting is a promising approach for solar energy to chemical energy conversion. However, the development of highly stable and efficient photoanodes still remains a great challenge. Here we demonstrate an ultrastable Ta₃N₅ photoanode modified with an AlO_x dielectric layer and a hole storage layer (ferrihydrite, Fh). It is found that the AlO_x layer not only reduces the formation of interfacial trap states of Ta₃N₅, but also promotes the separation of photogenerated charges. This bilayer synergistically promotes the extraction and transfer of photogenerated holes from Ta₃N₅ to the NiFeO_x cocatalyst. As a result, the Ta₃N₅ based photoanode exhibits significant inhibition of photocorrosion, and achieves an ultrastable photocurrent generation of 11.8 mA cm⁻² at 1.23 V vs. the reversible hydrogen electrode (RHE) over 120 hours. This work reveals the crucial role of the AlO_x dielectric layer in rational interface engineering of photoelectrodes.