Effects of interfacial layers on the photoelectrochemical properties of tantalum nitride photoanodes for solar water splitting

Abstract

This work describes the effects of interlayers on the structural, crystalline and photoelectrochemical properties of Ta₃N₅ photoanodes. Nb₄N₅ interlayers with different thicknesses are formed between Ta₃N₅ films and Ta back substrates using a thin film transfer method. Zone-axis images and electron diffraction patterns of cross-sections of the resulting Ta₃N₅/Nb₄N₅/Ta/Ti electrodes acquired by transmission electron microscopy evidence the formation of a 200 nm thick oriented Ta₃N₅ grain layer in the vicinity of the interlayer. This oriented Ta₃N₅ layer promotes electron transport throughout the Ta₃N₅ film. As a result, a Ta₃N₅ photoanode incorporating a Nb₄N₅ interlayer exhibits a higher photocurrent during the oxygen evolution reaction. These results obtained using the Ta₃N₅/interlayer/substrate configuration elucidate the key role played by the buffer layer in achieving efficient water splitting with Ta₃N₅ photoelectrodes.