Facile construction TiO2/ZnIn2S4/Zn0.4Ca0.6In2S4 ternary hetero-structure photo-anode with enhanced photo-electrochemical water-splitting performance

Constructing hetero-junction on TiO 2 is an effective way to overcome the fast charge recombination and slow charge transfer kinetics, but how to design the junction is still a significant challenge in photo-electrochemical (PEC) water splitting. In this study, a considerable improvement in PEC performance for TiO 2 nanotubes was achieved following the introduction of a ternary hetero-junction through depositing ZnIn 2 S 4 (ZIS) and Zn 0.6 Ca 0.4 In 2 S 4 (ZCIS) in sequence via a facile hydrothermal method (TiO 2 /ZIS/ZCIS). The optimized photo-anode exhibited a photocurrent density of 1.07 mA cm −2 at 1.23 V vs. reversible hydrogen electrode (RHE), to be 3.96 and 1.25 times enhanced compared to that of TiO 2 and TiO 2 /ZIS, respectively. Meanwhile, the incident photon-to-current conversion efficiency (IPCE) and applied bias photon-to-current efficiency (ABPE) of TiO 2 /ZIS/ZCIS were also increased in contrast with its counterparts. The merits of appropriate band alignment of TiO 2 , ZIS, and ZCIS and fewer interface defects built an internal electric field among the ternary hetero-junction, leading to an enhanced conductivity and efficient interface charge separation. These results were supported by a series of photo-electrochemical measurements. Among others, the shortened average lifetime of photo-generated electron-hole pairs from 1.51 (TiO 2 ) to 1.17 ns (TiO 2 /ZIS/ZCIS) according to time-resolved photoluminescence reveals that the charge carriers generated in TiO 2 would have an additional decay pathway in the hetero-structure, which benefits for the charge separation. Our strategy could be extended to many low-efficiency semiconductors for the design and synthesis of effective photo-anodes in PEC water splitting.