Amorphous Fe2O3 for photocatalytic hydrogen evolution

Abstract

Fe₂O₃ has drawn significant attention in photocatalysis due to its natural abundance, thermodynamic stability, environmental compatibility, low toxicity and narrow bandgap. Here, for the first time, we demonstrate that amorphous Fe₂O₃ nanoparticles can act as efficient and robust photocatalysts for solar H₂ evolution without any cocatalysts. We also establish a plausible mechanism involving the amorphization-induced thermodynamic and dynamic behaviors of amorphous Fe₂O₃ upon photocatalytic hydrogen evolution. Thermodynamically, amorphization provides more surface states and larger carrier density, and thus elevates the conduction band edge to go across the H₂ evolution potential level. Dynamically, amorphization-induced crystal field splitting weakening delocalizes the photogenerated carriers, and thus overcomes the excitation-wavelength-dependent small polaron trapping effect. These findings imply that amorphization may be a promising approach to functionalize and tailor other photocatalysts.