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 ∼3 nm, the increase in the particle size of ZrO₂ from ∼7 nm to ∼55 nm caused significant decrease in the reaction rate. When the particle size of ZrO₂ was fixed at ∼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.