Cl− ions accelerating interface charge transfer in a Si/In2S3 Faradaic junction photocathode for solar seawater splitting

Photoelectrocatalytic seawater splitting is a promising low-cost method to produce green hydrogen in a large scale. The effects of Cl − ions in seawater on the performance of a photoanode have been reported in previous studies. However, few researches have been done on the roles of Cl − ions in a photocathode. Herein, for the first time, we find that Cl − ions in the electrolyte improve the photocurrent of a Si/In 2 S 3 photocathode by 50% at −0.6 V RHE . An in-situ X-ray photoelectron spectroscopy (XPS) characterization combined with the time-of-flight secondary-ion mass spectrometry by simulating photoelectrochemical conditions was used to investigate the interface charge transfer mechanism. The results suggest that there is an In 2 +3 S 3− x (OH) 2 x layer on the surface of In 2 S 3 in the phosphate buffer solution (PBS) electrolyte, which plays a role as an interface charge transfer mediator in the Si/In 2 S 3 photocathode. The In 2 +3 S 3− x (OH) 2 x surface layer becomes In 2 +3 S 3− x (Cl) 2 x in the PBS electrolyte with NaCl and accelerates the charge transfer rate at the In 2 S 3 /electrolyte interface. These results offer a new concept of regulating interface charge transfer mediator to enhance the performance of photoelectrocatalytic seawater splitting for hydrogen production.