A DFT study of the hematite surface state in the presence of H2, H2O and O2

Hematite materials are of crucial interest since they are involved in many physico-chemical applications. However, the alpha-Fe2O3 surface state depends on temperature and surrounding gas composition and pressure. The hydrogen, oxygen and water coverage, the structure and thermodynamic stability of (0001) alpha-Fe2O3 surfaces have been investigated in the DFT + U framework as a function of temperature and partial pressures taking into account the spin effect. In the 300-900 K temperature range, it is mandatory to take into account water adsorption: the outermost iron atoms will be almost fully hydroxylated decreasing the acidic (Lewis) character of the surface. The chemistry of the surface will be dominated by hydrogen bonds. Above 900 K, only the Fe-termination and simply hydrogenated terminations are stable and must be considered. (C) 2013 Elsevier B.V. All rights reserved.