Microkinetic Modeling for Water-Promoted CO Oxidation, Water−Gas Shift, and Preferential Oxidation of CO on Pt

A comprehensive surface reaction mechanism on Pt is presented that is capable of describing CO oxidation, H2 oxidation, water−gas shift (WGS), preferential oxidation (PROX) of CO, and the promoting role of H2O on CO oxidation reasonably well. This mechanism consists of a literature CO oxidation model, a surface reaction mechanism for H2 oxidation on Pt developed here, and coupling reactions between the CO and H2 chemistries included for the first time. Thermodynamic consistency, which is shown to be essential for WGS, is ensured in all steps of the entire mechanism. The CO−H2 coupling via the CO + OH reaction, which may involve direct CO2 formation, CO* + OH* ↔ CO2* + H*, as well as an indirect pathway via the carboxyl intermediate, is explored. It is shown that this coupling plays a significant role in capturing the promoting effect of H2O on the CO oxidation-temperature-programmed reaction experiments at low temperatures as well as the overall speed of the WGS and PROX reactions. With the parameters use...