Theoretical study of solvent effects on the decomposition of formic acid over a Co(111) surface

Abstract

Solvent effects on the decomposition of formic acid over a Co(111) surface were studied via density functional theory calculations combined with a continuum implicit solvation model. The solvents used here were water, methanol, and acetone. The adsorption energies of key intermediates, the activation barriers and the rate and equilibrium constants of various elementary reactions in vacuum and in the solvents were obtained. Solvent presences decrease the adsorption energies of species. Formic acid decomposition on the surface goes through HCOO rather than COOH both in vacuum and in the solvents. The most favorable decomposition pathways in vacuum and in acetone are HCOOH → HCOO → HCO → CO. The corresponding rate determining steps are HCOO deoxidation to HCO with activation barriers of 0.78 and 0.76 eV, respectively. In the presences of water and methanol, the preferred pathways are shifted to HCOOH → HCOO → HCOO-m → CO2 below 750–800 K. Above those temperatures, the path of HCOOH → HCOO → HCO → CO becomes dominant again.