Realization of electrolyte interface effect on Bi2Te3 implanted flake-like ZnO thin films for understanding the highly stable PEC water splitting under simulated solar light and visible light

Abstract

This study aimed to rationally design the novel Bi2Te3 implanted ZnO (Bi2Te3@ZnO) thin films using simultaneous RF and DC magnetron sputtering technique. Herein, we explored the electrolyte interface effect (0.1 M of KOH, KCl, Na2SO3 and Na2SO4) on ZnO and Bi2Te3@ZnO towards highly stable PEC water splitting activity for the first time. Specifically, morphological evolution and electrolyte ion diffusion properties play a crucial role in realizing the prolonged charge carrier lifetime. Moreover, Bi2Te3@ZnO is highlighted with unique nanocone-shaped morphology compared to flake-like ZnO. Also, constructive interfacial interaction was observed between Bi2Te3 and ZnO. As a result, Bi2Te3@ZnO demonstrated superior and highly stable photocurrents in the KOH electrolyte compared to KCl, Na2SO3 and Na2SO4 electrolytes. Precisely, Bi2Te3@ZnO triumphed highly stable photocurrents about 7.93 x 10(-4) A cm(-2) compared to ZnO (6.02 x 10(-4)) at +0.4 V under solar light in KOH electrolyte. Accordingly, Bi2Te3@ZnO achieved remarkable photoconversion efficiency (eta) about 0.65 %, which is enabled by the strengthened intimate interaction between Bi2Te3 and ZnO. Furthermore, we compared the PEC activity under visible light (UV cut-off solar light). These results highlighted that the photoconversion efficiency difference between Bi2Te3@ZnO and ZnO (about 4 times) under visible light is relatively higher than solar light (1.3 times) in KOH. Thus, we proposed different charge carrier generation mechanisms of Bi2Te3@ZnO under solar and visible light. Therefore, intimate interfacial interaction, surface modification, ion diffusion and photoelectrode-electrolyte interaction are key parameters to enhance the PEC activity. Overall, rational design of the transition metal oxide/thermoelectric material interface using Bi2Te3@ZnO composite paves a new path towards highly stable photoanode during PEC water splitting activity in the KOH electrolyte environment.