Enhanced Carrier Transfer Dynamics via Metalloporphyrin‐Mediated Charge Distribution Modulation on Heterojunction Photoelectrodes

Using porphyrin as an interfacial charge mediator on a photoelectrode has been demonstrated to enhance photogenerated charge separation and photoelectrochemical (PEC) charge transport kinetics performance. However, the mechanism of boosting charge transfer is rarely explored. Notably, whether the charge distribution of metal-free porphyrins and metalloporphyrins influences photogenerated charge transfer is still ambiguous. Herein, TiO₂/Au/5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin-Zn (TiO₂/Au/ZnTPPS₄) and TiO₂/Au/5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TiO₂/Au/TPPS₄) nanocomposites are constructed by a simple hydrothermal synthesis method to study the charge separation and transfer behavior of ZnTPPS₄ and TPPS₄. The as-designed TiO₂/Au/ZnTPPS₄ exhibits remarkable performance (3.2 times) in PEC activity in comparison with TiO₂/Au/TPPS₄. Simultaneously, the scanning photoelectrochemical microscope (SPECM) is used to directly reveal charge transfer kinetics information by the in situ scanning probe technique. Specifically, TiO₂/Au/ZnTPPS₄ exhibits the highest charge transfer kinetics rate constant (12.57 × 10^-2 cm s^-1), corresponding to at least 3.4 times increase as compared with pure TiO₂ (3.71 × 10^-2 cm s^-1). This work highlights that metalloporphyrin accelerates charge transfer in TiO₂/Au/ZnTPPS₄ nanocomposites by changing charge distribution. These findings provide a new insight into enhancing PEC activity by a high-efficiency charge separation means with metalloporphyrins.