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.