Efficient Bipolar Hydrogen Peroxide Production Through Photoelectrochemistry

Hydrogen peroxide (H₂O₂) is a crucial environmentally benign oxidant. Photoanodes in bias-free photoelectrochemical (PEC) systems suffer from poor H₂O₂ selectivity at low potentials, limiting the efficiency of bipolar H₂O₂ production. Herein, we report a rare-earth ytterbium oxide (YbO_x) modified BiVO₄/WO₃ photoanode for efficient PEC water oxidation to H₂O₂. The optimized photoanode achieves a photocurrent density of 4.83 mA cm^-2 at 1.23 V_RHE, an H₂O₂ Faradaic efficiency (FE) of over 80% across the potential range of 0.6-1.8 V_RHE, and a peak FE of 90.4% at 1.6 V_RHE. Yb³⁺ Lewis acid sites suppress the competitive four-electron oxygen evolution reaction by forming Yb-hydroxyl complexes, while YbO_x enhances charge transfer and reduces interfacial resistance. Importantly, when coupled with a FeZnWMnYb high-entropy amorphous oxide cathode for the two-electron oxygen reduction reaction, the bias-free tandem cell achieves ∼160% bipolar H₂O₂ FE. Scaling the photoelectrode to 20 cm² under 0.7 suns illumination yields an H₂O₂ production rate of 3.03 mmol L^-1 h^-1. This work demonstrates a viable strategy for large-scale solar-driven H₂O₂ synthesis for environmental applications.