Unraveling the Role of the Rh-ZrO2 Interface in the Water-Gas-Shift Reaction via a First-Principles Microkinetic Study

The industrially important water-gas-shift (WGS) reaction is a complex network of competing elementary reactions in which the catalyst is a multicomponent system consisting of distinct domains. Herein, we have combined density functional theory calculations with microkinetic modeling to explore the active phase, kinetics, and reaction mechanism of the WGS over the Rh-ZrO2 interface. We have explicitly considered the support and metal and their interface and find that the Rh-ZrO2 interface is far more active toward WGS than Rh(111) facets, which are susceptible to CO poisoning. CO2 forming on the zirconia support rapidly transforms into formate. These findings demonstrate the central role of the interface in the water-gas-shift reaction and the importance of modeling both the support and the metal in bifunctional systems.