Reactivity of hydrogen and methanol on (0 0 1) surfaces of WO₃, ReO₃, WO₃/ReO₃ and ReO₃/WO ₃

Bulk tungsten trioxide (WO₃) and rhenium trioxide (ReO ₃) share very similar structures but display different electronic properties. WO₃ is a wide bandgap semiconductor while ReO₃ is an electronic conductor. With the advanced molecular beam epitaxy techniques, it is possible to make heterostructures comprised of layers of WO₃ and ReO₃. These heterostructures might display reactivity different than pure WO₃ and ReO₃. The interactions of two probe molecules (hydrogen and methanol) with the (0 0 1) surfaces of WO₃, ReO₃, and two heterostructures ReO ₃/WO₃ and WO₃/ReO₃ 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 ReO₃ is stronger than with pure WO₃ and the strength of the interaction substantially changes on the WO₃/ReO₃ and ReO₃/WO₃ heterostructures. The reaction barriers for decomposition and recombination reactions are sensitive to the nature of heterostructure. The calculated adsorption energy of methanol on WO₃(0 0 1) of -65.6 kJ/mol is consistent with the previous experimental estimation of -67 kJ/mol. © 2011 Elsevier B.V. All rights reserved.