Unassisted Photoelectrochemical H₂O₂ Production with In Situ Glycerol Valorization Using α-Fe₂O₃

Photoelectrochemical (PEC) H₂O₂ production via two-electron O₂ reduction is promising for H₂O₂ production without emitting CO₂. For PEC H₂O₂ production, α-Fe₂O₃ is an ideal semiconductor owing to its earth abundance, superior stability in water, and an appropriate band gap for efficient solar light utilization. Moreover, its conduction band is suitable for O₂ reduction to produce H₂O₂. However, a significant overpotential for water oxidation is required due to the poor surface properties of α-Fe₂O₃. Thus, unassisted solar H₂O₂ production is not yet possible. Herein, we demonstrate unassisted PEC H₂O₂ production using α-Fe₂O₃ for the first time by applying glycerol oxidation, which requires less bias compared with water oxidation. We obtain maximum Faradaic efficiencies of 96.89 ± 0.6% and 100% for glycerol oxidation and H₂O₂ production, respectively, with high stability for 25 h. Our results indicate that unassisted and stable PEC H₂O₂ production is feasible with in situ glycerol valorization using the α-Fe₂O₃ photoanode.