Insight into the complexation mechanism between a BiVO₄ photoanode and tartaric acid for efficient photoelectrochemical H₂ production

Recently, a super-active BiVO4-tartaric acid (C4H6O6) PEC fuel cell with efficient charge and energy transfer paths has been reported. However, the detailed complexation mechanism between BiVO4 and C4H6O6 remains unclear. Herein, a series of theoretical calculations and experiments are conducted to gain deep insight into the complexation mechanism. The results show that the optimal metal complexation site (Bi3+) of C4H6O6 involved in the VB contribution of the BiVO4 photoanode is crucial for significantly enhancing the PEC performance, which is beneficial for increasing the photoelectric conversion of BiVO4 and the energy release of C4H6O6. The BiVO4-C4H6O6 PEC fuel cell exhibits remarkable PEC performance with a current density of 13.75 mA cm(-2) at 1.23 V vs. the reversible hydrogen electrode (RHE) under AM 1.5 G irradiation. The Bi2WO6-C4H6O6 and CuWO4-C4H6O6 PEC fuel cells with similar complexation sites and energy band configurations to the BiVO4-C4H6O6 PEC fuel cell can also achieve improved PEC activity. This work provides an in-depth understanding of the complexation mechanism in the C4H6O6-based PEC fuel cell and can inspire the design of efficient PEC fuel cells.