Midtemperature CO₂ Deoxygenation to CO over Oxygen Vacancies of Doped CeO₂

CO 2 capture and utilization are a must for easing the global warming caused by the use of fossil fuels. Previous studies demonstrate the possibility of thermal deoxygenation of CO 2 to CO over the vacancies of CeO 2 . This study examines the influence of the dopant to CeO 2 on the deoxygenation of CO 2 to CO, wherein the examined dopants include Zr, Gd, Sm, and In. Only In-doped CeO 2 exhibits significant reactivity for CO 2 deoxygenation in our sequential temperature-programmed reduction (TPR) and CO 2 -TPRx (temperature-programmed reaction) tests up to 700 °C. In 0.5 Ce 0.5 O y after H 2 -TPR demonstrates a deoxygenation onset temperature as low as 400 °C and it can maintain a stable performance in cycle tests. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses indicate that In exsolutes from the fluorite framework during TPR and the exsoluted In 0 become oxidized in the subsequent CO 2 deoxygenation reaction. XPS indicates that the redox of Ce also occurs during TPR-CO 2 -TPRx with In 0.5 Ce 0.5 O y . In 2 O 3 by itself demonstrates a higher deoxygenation onset temperature, a lower per gram deoxygenation capacity, and a poorer stability than In 0.5 Ce 0.5 O y under the same test conditions, while CeO 2 is inactive. The results suggest a synergy between exsoluted In and the fluorite substrate, leading to the observed deoxygenation activity of In-doped CeO 2 .