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

As an n-type narrow band gap ternary sulfide semiconductor, CdIn2S4 exhibits favourable photoelectrochemical (PEC) water splitting performance. However, severe photogenerated carrier recombination and slow surface dynamics at the interface of monomer CdIn2S4 restrict its application. Herein, we addressed the problem by fabricating a TiO2/CdIn2S4-annealed photoanode by two-step anodization method, hydrothermal method and annealing treatment. As a result, the TiO2/CdIn2S4-annealed photoanode exhibited 6.21 mA/cm(2) at 1.23 V vs. RHE, which was much higher than the pure CdIn2S4 (0.05 mA/cm(2)) and TiO2 (0.14 mA/cm(2)), and was 9 times higher than TiO2/CdIn2S4 (0.68 mA/cm(2)). This excellent performance can be attributed to the synergistic effect of interfacial charge regulation (introducing TiO2 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 CdIn2S4 were simultaneously extracted in opposite directions. Experimental characterizations confirmed the introduction of TiO2 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 CdIn2S4.

Automated summary

This study addresses the issues of carrier recombination and slow surface dynamics of CdIn2S4 by fabricating a TiO2/CdIn2S4-annealed photoanode. The TiO2/CdIn2S4-annealed photoanode exhibits excellent PEC water splitting performance, with a much higher current density compared to pure CdIn2S4 and TiO2.