Theoretical study of the decomposition of methyl formate on copper surface

• The degradation of ester lubricants on copper surface was examined using density functional theory . • Methyl formate was adopted as a model compound of the ester lubricants, and its interaction with the copper surface was investigated. • The decomposition routes of methyl formate on the Cu(111) surface was analyzed. • The strategy to enhance the durability of ester lubricant was proposed based on the decomposition routes of methyl formate. Ester lubricants have wide industrial applications due to their suitable lubricating properties. However, they may degrade under the high temperatures and with the catalysis of the metal surface. This study employs density functional theory to investigate the effect of a copper surface on the decomposition of methyl formate (MF), a model compound of ester lubricant. The results show that the dehydrogenation of the adsorbed MF (MF*) to produce the adsorbed methoxycarbonyl (COOCH 3 *) is the dominant reaction. COOCH 3 * then readily dissociates into CO* and CH 3 O* by overcoming a low energy barrier of 0.12 eV. Breakages of other bonds should contribute marginally to the decomposition of COOCH 3 *, with their high energy barriers. For the practical ester lubricants that are non-formate, the decompositions may be initiated by the adsorptions through the carbonyl oxygen atom on the copper surface. Hence, modifying the structure on the carbonyl side is anticipated to enhance the durability of the ester lubricants.