三种Au(111)催化水煤气变换反应机理的比较

采用密度泛函理论对三种水煤气变换反应(WGSR)机理(氧化还原机理、羧基机理、甲酸基的生成机理)在Au(111)面上的反应历程进行详细讨论.通过对表面吸附物种(H2O、CO、OH、O、H、CO2、COOH、HCOO)的吸附行为进行研究,得到最佳活性吸附中心.对三种机理中的14个基元反应的活化能进行分析,得出WGSR在Au(111)上按照羧基机理和氧化还原机理进行的可能性较大,按照甲酸基的生成机理进行的可能性较小.相比较羧基机理和氧化还原机理,反应更有可能按照羧基机理进行,最佳反应途径为H2O-H→OH+CO→COOH+OH→CO2.

Comparison of Three Reaction Mechanisms for the Water Gas Shift Reaction on Au(111)Surface

A detailed density functional theory (DFT) investigation revealed three possible mechanisms (redox mechanism, carboxyl mechanism, and formate intermediate mechanism) for the water-gas shift reaction on Au(111) surface. All the pertinent species (H2O, CO, OH, O, H, CO2, COOH, HCOO) were calculated. We obtained their preferred adsorption sites. We characterized the reaction pathway containing 14 elementary steps and calculated the reaction potential energy surfaces. The calculation results show that the carboxyl mechanism and the redox mechanism are feasible while the formate intermediate mechanism is unlikely because of its high formation barrier. Our calculations also show that the carboxyl mechanism is more probable compared with the redox mechanism and the most feasible reaction pathway is H2O→-H OH→+COCOOH→+OHCO2.