Coke Management: Unveiling the Role of Ce Substitution in Gd ₂ Zr _1.8 Ni _0.2 O _7−δ Catalyst for Dry Reforming of Methane

The redox characteristics of cerium have become crucial elements in the carbon gasification process during methane dry reforming. This work examines the effect of cerium substitution in the Gd2Zr1.8Ni0.2O7−δ catalyst during methane dry reforming, employing a range of Ce-substituted Gd2Zr1.8–xNi0.2CexO7−δ (x = 0.1, 0.2, 0.5, 0.75) catalysts synthesized via the citrate gel method. The materials crystallized in a fluorite structure, as verified by X-ray diffraction analysis and Raman spectroscopy. Enhanced reducibility of the substituted catalysts was assessed through H2-temperature-programmed reduction analysis. CO2 and O2 desorption studies along with X-ray photoelectron spectroscopy validated the enhanced basicity and generation of active oxygen and hydroxyl species. The enhanced activity and coke gasification in Gd2Zr1.6Ni0.2Ce0.2O7−δ catalyst are attributed to surface hydroxyl species, and prominent intermediate carbonate and bicarbonate species were further verified by in situ infrared spectroscopy. The high basicity of the Gd2Zr1.6Ni0.2Ce0.2O7−δ catalyst and high concentrations of oxygen vacancies (∼66.4%) enhances CO2 adsorption and desorption, resulting in continuous CO2 activation, leading to less carbon formation and superior activity of the catalyst. The Gd2Zr1.6Ni0.2Ce0.2O7−δ catalyst exhibits the highest CH4 and CO2 conversion rates, at 85% and 93.5%, respectively, and remains stable for 100 h. Postreaction analysis of Gd2Zr1.6Ni0.2Ce0.2O7−δ confirms structure stability and less carbon formation compared to other substituted catalysts in dry reforming of methane. This study demonstrates that the moderate concentration of Ce in the Gd2Zr1.6Ni0.2Ce0.2O7−δ catalyst exhibits balanced activity and coke gasification capacity in the dry reforming of methane for a longer duration.