Cl Species Transformation on CeO2(111) Surface and Its Effects on CVOCs Catalytic Abatement: A First-Principles Investigation

Cl species transformation and deactivation effects on ceria (111) model catalysts were investigated in the first-principles framework. Conventionally, the strong adsorption of Cl atom in the oxygen vacancy of ceria was believed to be the dominant deactivation factor. However, under the typical conditions of chlorinated volatile organic compounds (CVOCs) catalytic combustion, the deactivation was found to be hindered because of the high O-2/Cl ratio in the reactants' feed. Then, the possible formation pathways of Cl-2 and HCl during CVOCs catalytic abatement reaction were proposed. It was identified that the H-bond interaction between surface hydroxyls and Cl species was the key factor to control the selectivity in the final product of Cl species (HCl or Cl-2). By introduction H2O or other H resources, the coverage of surface OH radicals could be increased, which in turn benefits the conversion to HCl over Cl-2. However, the competitive adsorption between H2O and oxygen on vacancy would lead to somewhat of a loss of low-temperature catalytic activity.