Unassisted Photoelectrochemical H 2 O 2 Production with In Situ Glycerol Valorization Using α-Fe 2 O 3 .

Photoelectrochemical (PEC) H 2 O 2 production via two-electron O 2 reduction is promising for H 2 O 2 production without emitting CO 2 . For PEC H 2 O 2 production, α-Fe 2 O 3 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 O 2 reduction to produce H 2 O 2 . However, a significant overpotential for water oxidation is required due to the poor surface properties of α-Fe 2 O 3 . Thus, unassisted solar H 2 O 2 production is not yet possible. Herein, we demonstrate unassisted PEC H 2 O 2 production using α-Fe 2 O 3 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 H 2 O 2 production, respectively, with high stability for 25 h. Our results indicate that unassisted and stable PEC H 2 O 2 production is feasible with in situ glycerol valorization using the α-Fe 2 O 3 photoanode.