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 °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 °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 H2 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.