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

Abstract

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.