Interfacial [S─Cu─C] Bonds Induced π‐d Electron Coupling Toward Modulating Charge Transfer for Efficient Solar Water Oxidation

Abstract Regulating the interfacial electric field to achieve rapid charge transfer is crucial for superior photoelectrochemical water splitting. Herein, the ultra‐thin hydrogen‐substituted graphdiyne (HsGDY) is precisely assembled on the surface of CdS nanorod array (Cu‐CdS‐HsGDY) by an in situ polymerization strategy. The strong π‐d electron coupling is aroused by the delocalized π electrons of HsGDY and the delocalized d electrons of CdS through the interfacial [S─Cu─C] bonds. The strong interfacial electric field can effectively promote the charge localization distribution and reduce the charge transfer resistance. The optimized Cu‐CdS‐HsGDY photoanode obtain a photocurrent density as high as 4.83 mA cm ⁻² at 1.23 V versus reversible hydrogen electrode in neutral electrolyte solution under AM 1.5G illumination, which is 6.8 times that of the pristine CdS. Moreover, the photoanode maintains an initial photocurrent density of 84% within 4 h without any assistance of sacrificial agents, which is a rather competitive performance of similar sulfide photoanodes. The mechanism of strong π‐d electron coupling on interfacial charge transfer and surface reaction kinetics is investigated by transient spectroscopy measurements, density functional theory calculation, and finite element simulation analysis. This work provides new insights into designing a reasonable interface structure to regulate charge transfer for achieve efficient PEC water splitting.