First-Principles Microkinetic Study of Methanol Synthesis on Cu(221) and ZnCu(221) Surfaces

First-principle based microkinetic simulations are performed to investigate methanol synthesis from CO and CO2 on Cu(221) and CuZn(221) surfaces. It is found that regardless of surface structure, the carbon consumption rate follows the order: CO hydrogenation > CO/CO2 hydrogenation > CO2 hydrogenation. The superior CO hydrogenation activity mainly arises from the lower barriers of elementary reactions than CO2 hydrogenation. Compared to Cu(221), the introduction of Zn greatly lowers the activity of methanol synthesis, in particularly for CO hydrogenation. For a mixed CO/CO2 hydrogenation, CO acts as the carbon source on Cu(221) while both CO and CO2 contribute to carbon conversion on CuZn(221). The degree of rate control studies show that the key steps that determine the reaction activity of CO/CO2 hydrogenation are HCO and HCOO hydrogenation on Cu(221), instead of HCOOH hydrogenation on CuZn(221). The present work highlights the effect of the Zn doping and feed gas composition on methanol synthesis.