Visible Light-Driven H₂O₂ Photoelectrocatalytic Synthesis Over a Tandem Electrode Strategy

ABSTRACT: Photocatalytic synthesis of hydrogen peroxide (H₂O₂) can be an environmentally friendly and energy-saving solution. However, the oxygen reduction reaction (ORR) rate is limited due to the low solubility of O₂ in water. In this study, a modified BiVO₄ (BVO) photoanode combined with an Sn-coordinated phthalocyanine gas diffusion electrode (SnPc-GDE) was employed for the synthesis of H₂O₂, and the oxy-gen reduction reaction rate was increased through a unique three-phase interface system. When visible light was irradiated on the BVO photoanode, the hole-electron pairs were excited and the oxygen evolution reaction (OER) was driven through the holes, and the excited electrons were transferred to the SnPc-GDE to reduce O₂ for the synthesis of H₂O₂. Oxygen vacancy enrichment on the BVO electrode was achieved by photoetching and annealing under an N₂ atmosphere, which effectively improved the carrier separation efficiency. Complexation with a WO₃ layer formed a built-in electric field, which further promoted the electron-hole pair separation. The SnPc catalyst-modified GDE electrode has the best selectivity for ORR and remains stable during long-term reactions. Under bias-free conditions, the generation rate of H₂O₂ reached 952.5 μM·L⁻¹·h⁻¹, with a Faradaic efficiency of 48.4%. This study provided a practical strategy for designing a highly efficient BVO/SnPc-GDE photoelectrochemical system to produce H₂O₂ based on improvement in electron-hole transmission efficiency and product selectivity.