Materials Research Express (Jan 2021)
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 Bi _2 Te _3 implanted ZnO (Bi _2 Te _3 @ZnO) thin films using simultaneous RF and DC magnetron sputtering technique. Herein, we explored the electrolyte interface effect (0.1 M of KOH, KCl, Na _2 SO _3 and Na _2 SO _4 ) on ZnO and Bi _2 Te _3 @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, Bi _2 Te _3 @ZnO is highlighted with unique nanocone-shaped morphology compared to flake-like ZnO. Also, constructive interfacial interaction was observed between Bi _2 Te _3 and ZnO. As a result, Bi _2 Te _3 @ZnO demonstrated superior and highly stable photocurrents in the KOH electrolyte compared to KCl, Na _2 SO _3 and Na _2 SO _4 electrolytes. Precisely, Bi _2 Te _3 @ZnO triumphed highly stable photocurrents about 7.93 × 10 ^–4 A cm ^−2 compared to ZnO (6.02 × 10 ^–4 ) at +0.4 V under solar light in KOH electrolyte. Accordingly, Bi _2 Te _3 @ZnO achieved remarkable photoconversion efficiency ( η ) about 0.65 %, which is enabled by the strengthened intimate interaction between Bi _2 Te _3 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 Bi _2 Te _3 @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 Bi _2 Te _3 @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 Bi _2 Te _3 @ZnO composite paves a new path towards highly stable photoanode during PEC water splitting activity in the KOH electrolyte environment.
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