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

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 × 10^–4 A cm⁻² compared to ZnO (6.02 × 10^–4) at +0.4 V under solar light in KOH electrolyte. Accordingly, Bi₂Te₃@ZnO achieved remarkable photoconversion efficiency (η) 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. (paper)