Theoretical study of the decomposition of HCOOH on an MgO(100) surface

Abstract

We present here a theoretical investigation of the mechanism of the decomposition of formic acid on perfect and defective MgO(100) surfaces using the ab initio molecular orbital method. The decomposition reaction does not occur on a perfect surface, but is feasible on defect surfaces: the surface with an O 2− vacancy is more favorable than the surface with an O vacancy. Although the mechanism is different from that in the gas phase, C–H and C–O bond cleavages occur at the same time in the transition state, as in the gas phase. The carbonyl O atom moves into the vacancy to form an intermediate structure. The intermediate is more stable by 41.7 kcal mol −1 at the UMP2 level than the bridging structure. The C–H interacts with the lattice O atom to form a surface OH species. The interaction between the C–H and lattice Mg atoms is repulsive. The energy barrier is 28.3 kcal mol −1 and the overall reaction is endothermic by 48.9 kcal mol −1 at the UMP2 level.