Interfacial charge and surface defect regulation for high-efficiency CdIn2S4-based photoanodes

As an n-type narrow band gap ternary sulfide semiconductor, CdIn 2 S 4 exhibits favourable photoelectrochemical (PEC) water splitting performance. However, severe photogenerated carrier recombination and slow surface dynamics at the interface of monomer CdIn 2 S 4 restrict its application. Herein, we addressed the problem by fabricating a TiO 2 /CdIn 2 S 4 -annealed photoanode by two-step anodization method, hydrothermal method and annealing treatment. As a result, the TiO 2 /CdIn 2 S 4 -annealed photoanode exhibited 6.21 mA/cm 2 at 1.23 V vs . RHE, which was much higher than the pure CdIn 2 S 4 (0.05 mA/cm 2 ) and TiO 2 (0.14 mA/cm 2 ), and was 9 times higher than TiO 2 /CdIn 2 S 4 (0.68 mA/cm 2 ). This excellent performance can be attributed to the synergistic effect of interfacial charge regulation (introducing TiO 2 NTs as electron transport layer) and surface defect regulation (introducing sulfur vacancies as OER active centers to facilitate hole transport). By this way, the photogenerated electrons and holes of CdIn 2 S 4 were simultaneously extracted in opposite directions. Experimental characterizations confirmed the introduction of TiO 2 and sulfur vacancies can enhance the separation and injection efficiency of carriers. This work provides a new idea for regulating interface charges and surface defects to improve the PEC activity of CdIn 2 S 4 .