Fe2O3/C-C3N4-Based Tight Heterojunction for Boosting Visible Light-Driven Photocatalytic Water Oxidation

Recently, photocatalytic water splitting for clean hydrogen (H-2) energy through the use of solar energy has been considered to be a promising means of renewable energy conversion. Because of the high activation barriers of oxygen (O-2) generation, the half reaction, i.e., water oxidation, is the rate-limiting steps of the overall water splitting efficiency. Photocatalysts with high activity and nonmetal usage are needed. Herein, we report one new thin-layered heterojunction sample of Fe2O3/C-C3N4, containing layered alpha-Fe2O3 and carbon-coated g-C3N4, obtained through one simple repeatable solid-state synthesis strategy. The layered FeOOH and g-C3N4 are first synthesized working as the precursors. Under N-2 atmosphere and 580 degrees C, the dehydration of FeOOH happens, and it transfers into layered alpha-Fe2O3; the water vapor destroys the van der Waals force of g-C3N4 and induces the parts of edge carbonization. Under the synergistic effect of vapor and heating, the thin-layered Fe2O3/C-C3N4 heterojunction is obtained. Without cocatalyst addition, the obtained sample shows efficient visible-light-driven photocatalytic water oxidation performance, i.e., a 22.3 mu mol/h oxygen evolution rate under the LED lamp of lambda = 420 nm illumination, 3, 16, and 30 times higher than reference Fe2O3/C3N4, bare alpha-Fe2O3, and g-C3N4, respectively. The key parameters for the enhanced photocatalytic activity can be attributable to the carbon layer and the tight contact structure, which can work as the carrier (electrons from g-C3N4 and holes from alpha-Fe2O3) collection center and provide the small migration resistance. Moreover, the carbon shows a different migration rate for electrons and holes and then facilitates the separation of carriers to some extent. To our knowledge, no other papers on Fe2O3/C-C3N4-based photocatalytic water oxidation have been reported. This work can provide a new insight for synthesis of g-C3N4-based photocatalysts, and also help us understand the water oxidation reaction.