Hydrogen generation by water splitting on hematite (0001) surfaces: first-principles calculations.

The surface chemical activity is a critical factor affecting the photocatalytic efficiency of hematite. In this study, we investigate systematically the reaction kinetics of water heterolytic dissociation (H2O-OH(-) + H(+)) and hydrogen generation by water splitting on four kinds of hematite (0001) surfaces, namely perfect and defective O- and Fe-terminated surfaces, at the electronic level based on first-principles calculations. The simulation results illustrate that the chemical reaction rate for the dissociation and hydrogen generation is sensitive to the morphology of the hematite (0001) surface. For water heterolytic dissociation, the hydrogen atom is apt to drop from water molecules on the perfect O-terminated (0001) surface without energy consumption. However, the Fe-terminated (0001) perfect surface is a preferable candidate for hydrogen generation, on which the whole photoelectrochemical process needs to overcome a rate determined barrier of 2.77 eV. Our investigation shows that O- or Fe-vacancy on hematite (0001) surfaces is not conductive to hydrogen generation by water splitting.