Reactivity of hydrogen and methanol on (0 0 1) surfaces of WO 3, ReO 3, WO 3/ReO 3 and ReO 3/WO 3

Abstract

Bulk tungsten trioxide (WO 3) and rhenium trioxide (ReO 3) share very similar structures but display different electronic properties. WO 3 is a wide bandgap semiconductor while ReO 3 is an electronic conductor. With the advanced molecular beam epitaxy techniques, it is possible to make heterostructures comprised of layers of WO 3 and ReO 3. These heterostructures might display reactivity different than pure WO 3 and ReO 3. The interactions of two probe molecules (hydrogen and methanol) with the (0 0 1) surfaces of WO 3, ReO 3, and two heterostructures ReO 3/WO 3 and WO 3/ReO 3 were investigated at the density functional theory level. Atomic hydrogen prefers to adsorb at the mono-coordinated O (O 1C) sites forming a surface hydroxyl on four surfaces. Dissociative adsorption of a hydrogen molecule at the O 1C site leads to formation of a water molecule adsorbed at the penta-coordinated metal (M 5C) site. This is thermodynamically the most stable state. A thermodynamically less stable dissociative state involves two surface hydroxyl groups O 1CH and O 2CH. The interaction of molecular hydrogen and methanol with pure ReO 3 is stronger than with pure WO 3 and the strength of the interaction substantially changes on the WO 3/ReO 3 and ReO 3/WO 3 heterostructures. The reaction barriers for decomposition and recombination reactions are sensitive to the nature of heterostructure. The calculated adsorption energy of methanol on WO 3(0 0 1) of −65.6 kJ/mol is consistent with the previous experimental estimation of −67 kJ/mol.