Investigation of the influence for ZnSe phase in Ag2ZnSnSe4 and ZnO/Ag2ZnSnSe4 photoanodes on their photoelectrochemical activities in salt water solution

Abstract

In this study, quaternary Ag2ZnSnSe4 (AZTSe) photoanodes with low and high ratios of ZnSe phase are made to understand the influence on the charge-transfer mechanisms, reaction kinetics and photoelectrochemical activities in electrolyte. Photoelectrochemical activities of 7.5 and 5.25 mA/cm2 at the given voltage of 1 V (vs. Ag/AgCl) are obtained using the AZTSe sample containing low ratio (atomic percentage of around 21% in sample) and high ratio (atomic percentage of around 37% in sample) of ZnSe phase, respectively. From the electrochemical measurements and X-ray absorption spectra of samples, the ZnSe phase can attract the light-driven electrons from the sample with low ratio of ZnSe phase (atomic percentage of 21% in sample). However, for the sample containing high ratio of ZnSe phase (atomic percentage of 37% in sample), the ZnSe acts as the recombination center and results in poor photoelectrochemical activity. With the modification of ZnO rods on sample, its long-term photoelectrochemical activity is improved due to high charge transportation kinetic and photo-driven holes accumulation on ZnO rods rather than on AZTSe sample. Our study reports a significant observation on the influence of ZnSe phase for photoelectrochemical salt-water splitting.