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/In₂S₃ 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 In₂⁺³S_3−x(OH)_2x layer on the surface of In₂S₃ in the phosphate buffer solution (PBS) electrolyte, which plays a role as an interface charge transfer mediator in the Si/In₂S₃ photocathode. The In₂⁺³S_3−x(OH)_2x surface layer becomes In₂⁺³S_3−x(Cl)_2x in the PBS electrolyte with NaCl and accelerates the charge transfer rate at the In₂S₃/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.

光电催化海水分解是一种有前途的大规模生产绿色氢气的低成本方法。先前的研究已经报道了海水中的 Cl ⁻ 离子对光电阳极性能的影响。然而，关于Cl ⁻ 离子在光电阴极中的作用的研究很少。在此，我们首次发现电解质中的 Cl ⁻ 离子使 Si/In ₂ S ₃ 光电阴极的光电流在−0.6V _RHE 。通过模拟光电化学条件，采用原位 X 射线光电子能谱（XPS）表征结合飞行时间二次离子质谱来研究界面电荷转移机制。结果表明，In ₂ ⁺³ S _3−x (OH) _2x 层。 /b10> S ₃ 在磷酸盐缓冲溶液（PBS）电解质中，在 Si/In ₂ S ₃ 光电阴极。 In ₂ ⁺³ S _3−x (OH) _2x 表层变为In ₂ ⁺³ (Cl) _2x 在含有 NaCl 的 PBS 电解质中，加速 In ₂ S ₃ 处的电荷转移速率/电解质界面。这些结果提供了调节界面电荷转移介体的新概念，以提高光电催化海水分解制氢的性能。