DFT studies of the adsorption and decomposition of dimethyl ether on copper surface

Abstract

Polyethers are excellent lubricants in reducing friction and wear between tribological counterfaces. However, they may decompose at the high temperatures due to the friction. Besides, the metal surfaces or metal abrasives of the machines will act as catalysts in accelerating the degradation of polyethers. Dimethyl ether (DME) is the simplest ether and may act as a model for polyethers. In this work, the catalytic mechanism of copper surface, Cu(111), on the degradation of adsorbed DME on the Cu(111) surface (DME*) was studied theoretically, by using the density functional theory. The energetics and kinetics of the reactions of DME* decomposition on the Cu(111) surface were calculated. The results showed that there are three main routes dominating the decomposition of DME* on the Cu(111) surface, all initiated by the breakage of C H bond. These three routes may lead to the production of CO*, CH*, and H*, which are all tightly adsorbed on the Cu(111) surface and hence may deteriorate the performance of the machines. Kinetic analysis indicates that the C H bond connecting the C O bond in ether-based lubricants should be strengthened to improve the thermal stability of the lubricant.