CO2-ZrO2 interaction in CDRM: A combined experimental and theoretical study

Abstract

Stable CDRM performance of a catalyst is dominantly determined by its ability to dissociate CO2 to produce and utilize surface oxygen at rates high enough to clean surface carbon formed on its active sites. The current study is an attempt to understand the nature of CO2 activation on a commercial ZrO2, which is a widely used CDRM support responsible for CO2 dissociation and surface O mobility, via combined evaluation of computational and experimental findings. Accordingly, significant ZrO2-CO2 interaction, which is affected by temperature, was confirmed via FTIR-DRIFTS through surface bicarbonate, carbonate, formate and OH species as well as bridged CO detection. Though DFT calculations on periodic models revealed that upon CO2 adsorption at the possible active sites on stoichiometric m-ZrO2(1¯11) bidentate and tridentate carbonates were formed, a dissociative CO2 adsorption did not take place on the surface. Results of the DFT simulations performed on O–ZrO2 system has shown that m-ZrO2 surface enables oxygen mobility. Based on the results, CO2 dissociation on ZrO2 is proposed to occur on oxygen vacancy and defect sites verified by XPS analysis and/or via reversible formate formation/decomposition mechanism.