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 (YbOx) 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 VRHE, an H2O2 Faradaic efficiency (FE) of over 80% across the potential range of 0.6-1.8 VRHE, and a peak FE of 90.4% at 1.6 VRHE. Yb3+ Lewis acid sites suppress the competitive four-electron oxygen evolution reaction by forming Yb-hydroxyl complexes, while YbOx 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.