Oxygen Vacancies-Mediated CO2 Methanation Over Ni/CeO2-ZrO2 Solid Solutions Assembled on Clay Minerals

This paper reports the synthesis and CO2 methanation performance of Ni/CeO2-ZrO2 (CZ) solid solutions assembled on different clay minerals (rectorite, attapulgite, halloysite, and kaolin). The catalytic performance of the samples was examined in temperature range 200-400 degrees C at normal pressures. The attapulgite (ATP) assembled Ni nps-incorporated-CZ solid solution (Ni-CZA) has the highest CO2 conversion and excellent stability. The CO2 conversion of the Ni-CZA catalyst reached up to 81.2% at 400 degrees C, and CH4 selectivity was nearly 100%. The catalyst assembled on ATP has excellent adsorption performance and a large specific surface area, resulting in higher Ce3+ and adsorbed oxygen content, thanks to the high content of oxygen vacancies and faster oxygen transfer speed. Mechanistic analysis shows that the H-2 dissociates at the Ni site, the CO2 was decomposed into CO and O, and the ATP and CZ provide hydroxyls and oxygen vacancies, respectively, in this composite catalyst.