Au/ZrO2 catalysts for low-temperature water gas shift reaction: Influence of particle sizes

The size effects of Au and ZrO2 particles on the structural property and the catalytic performance of Au/ZrO2 catalysts for the water gas shift reaction were extensively investigated. It was found that the Au-ZrO2 contact boundaries played essential roles in determining the catalytic reactivity. By keeping the size of Au particle to be similar to 3 nm, the increase in the particle size of ZrO2 from similar to 7 nm to similar to 55 nm caused significant decrease in the reaction rate. When the particle size of ZrO2 was fixed at similar to 20 nm, the conversion of CO decreased greatly with increasing the size of gold particle from 2.9 to 6.2 nm. IR spectroscopy and kinetic study revealed that the water gas shift reaction occurred at the Au-ZrO2 contact boundaries, where CO is adsorbed on the Au species and H2O is activated on the surface of ZrO2 through the formation of formate species, acting as key reaction intermediates.