Photogenerated charge separation at BiVO 4 photoanodes enhanced by a Ag-modified porphyrin polymer skeleton.

Bismuth vanadate (BiVO 4 ) has been considered a promising photoactive material in photoelectrochemical (PEC) water-splitting systems. However, the performance of BiVO 4 -based photoanodes is currently unsatisfactory, indicating the need for new architectural designs to improve their efficiency. In this paper, a porphyrin-phosphazene polymer (THPP-HCCP) was synthesized with a sizeable conjugated structure, and Ag particles were deposited on its surface as an organic-inorganic composite interface improvement layer. The deposition of the composite polymer film on BiVO 4 resulted in a significant increase in photocurrent density, reaching up to 2.2 mA cm -2 (1.23 V vs. RHE), almost three times higher than pristine BiVO 4 , which benefits from the synergistic effect of Ag nanoparticles and porphyrin-phosphazene. Furthermore, photophysical and intensity-modulated photocurrent analysis demonstrated that the Ag-THPP-HCCP heterostructures could broaden the light-absorbing range and facilitate hole transfer to the semiconductor surface, resulting in an improved water oxidation process. The dynamic charge transport behavior of Ag-THPP-HCCP/BiVO 4 was investigated using scanning photoelectrochemical microscopy, which showed that the rate constant ( K eff ) exhibits an almost 4-fold increase compared to pristine BiVO 4 , indicating a significant improvement in the transport of photogenerated holes. This experiment presents a novel strategy for designing high-efficiency polymer-based photoanodes.