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

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.