ALD-grown oxide protective layers on Ta3N5–Cu2O n–p nanoarray heterojunction for improved photoelectrochemical water splitting

It is highly challenging for coating protective layers on nanoarray photoelectrodes to achieve efficient charge extraction and suppressing corrosion of the electrolyte. Herein, atomic layer deposition was used to deposit a composite overlayer of Al-doped ZnO and TiO2 onto a Ta3N5–Cu2O heterojunction nanoarray photoanode, exhibiting a low onset potential of 0.40 V vs reversible hydrogen electrode (RHE), a high photocurrent density of 4.61 mA·cm−2 at 1.23 V vs RHE, and improved photoelectrochemical (PEC) stability, with the help of CoOOH as a cocatalyst. The improved PEC performances would result from that both the oxide overlayer and the cocatalyst layer contribute to the efficient charge extraction and stopping the electrolyte permeation from/and into the semiconductor, passivating the surface states, and improving the energetics at electrode–electrolyte interface.