ZnIn2S4 thin films grown by pulsed laser deposition: Effect of electrolyte and illumination conditions on photoanode performance

This study presents a novel approach for fabricating ZnIn 2 S 4 (ZIS) thin films using pulsed laser deposition (PLD) and evaluates their performance as photoanodes for photoelectrochemical (PEC) water splitting. The ZIS layers, deposited on fluorine-doped tin oxide (FTO) glass, exhibited a smooth and homogeneous morphology, were semi-transparent, and demonstrated photoactivity under visible light. The influence of illumination direction and electrolyte pH on photocurrent generation and stability was investigated. The highest photocurrent value of 2.82 mA cm −2 was achieved in 0.5 M H 2 SO 4 under illumination directed on the photoactive layer, however, the electrode exhibited low stability in this electrolyte. In contrast, alkaline conditions (0.5 M NaOH) provided enhanced stability, with only a 5 % photocurrent decrease after 300 s, as no significant degradation was observed. A three-step degradation mechanism under acidic conditions was proposed, where the oxidation of S 2− to SO 4 2− initiated structural breakdown, followed by sulfate dissolution and the leaching of Zn and In. The results underline the role of electrolyte acidity in accelerating the degradation, particularly under prolonged illumination conditions. Future research should focus on enhancing ZIS durability through protective coatings, doping strategies, or modified electrolytes to mitigate degradation while maintaining high PEC performance.