Abstract
Density functional theory calculations were carried out to examine the mechanism of ethanol decomposition on the Rh(211) surface. We found that there are two possible decomposition pathways: (1) CH3CH2OH -> CH3CHOH -> CH3COH -> CH3CO -> CH3 + CO -> CH2 + CO -> CH + CO -> C + CO and (2) CH3CH2OH -> CH3CHOH -> CH3COH -> CH2COH -> CHCOH -> CHCO -> CH + CO -> C + CO. Both pathways have a common intermediate of CH3COH, and the key step is the formation of CH3CHOH species. According to our calculations, the mechanism of ethanol decomposition on Rh(211) is totally different from that on Rh(111): the reaction proceeds via CH3COH rather than an oxametallacycle species (-CH2CH2O- for Rh( 111)), which implies that the decomposition process is structure sensitive. Further analyses on electronic structures revealed that the preference of the initial C-alpha-H path is mainly due to the significant reduction of d-electron energy in the presence of the transition state (TS) complex, which may stabilize the TS-surface system. The present work first provides a clear picture for ethanol decomposition on stepped Rh(211), which is an important first step to completely understand the more complicated reactions, like ethanol steam reforming and electrooxidation.