Methanol dissociation on bimetallic surfaces: validity of the general Brønsted–Evans–Polanyi relationship for O–H bond cleavage

Abstract

Density functional theory (DFT) calculations were employed to study the dissociation of the O–H bond in methanol on several planar and stepped bimetallic transition metal surfaces, composed of elements showing high or moderate activity towards this reaction, namely, Ni, Rh, Ru, Ir, Pd, Au, Zn and Cu. The activation energies for the O–H bond cleavage were compared with those estimated using a Brønsted–Evans–Polanyi (BEP) relationship for the RO–H bond breakage on pure metal transition surfaces, relating the activation energy for the reaction with the adsorption energies of the reaction products, RO˙ and H˙ adsorbed on the surface of the catalyst. Furthermore, the average differences between the values of the activation energies calculated with the exhaustive determination of the full reaction path and location of the transition state on each surface model and the activation energies obtained from the BEP relationship with the simple calculation of the adsorption energies of the RO˙ and H˙ species are ∼0.14 eV. This suggests that the BEP relationship developed upon the consideration of data for dissociation of the O–H bond in alcohols and water on pure metal surfaces is also valid for a qualitative prediction of the methanol activation energy on bimetallic surfaces.