NiOx-coated/Zn-doped CuO photoelectrodes with efficient charge transfer, protection from photocorrosion, and improved photocurrent density and photostability

Abstract

In this study, Zn-doped CuO photoelectrodes were fabricated to investigate whether Zn doping would improve the photocurrent density by enhancing crystallinity, reducing charge transfer resistance and producing more efficient charge transfer in CuO photoelectrodes. In particular, the photocurrent density of a 5 at% Zn-doped CuO photoelectrode was − 2.32 mA/cm2, which was significantly higher than that of a bare CuO photoelectrode (−1.54 mA/cm2). However, the photostability of the doped CuO photoelectrodes was still low at 55.2 %, so protective layers with various NiOx concentrations were deposited on the photoelectrodes, and their photostability was analyzed. By comparing the XPS Cu 2p spectra of bare CuO, 5 at% Zn-doped CuO and 0.045 at% NiOx-coated/5 at% Zn-doped CuO photoelectrodes measured before and after photostability measurements, we investigated the reduction of CuO, which causes photocorrosion. The results of this study showed that Zn doping and NiOx deposition greatly improved the structural, electrical and photoelectrical properties of the CuO photoelectrodes. The photostability of the 0.045 at% NiOx-coated/5 at% Zn-doped CuO photoelectrode was very high, at 92.9 %, and the photocurrent density also improved to − 2.47 mA/cm2.