Volcano-type trend between precipitation pH and catalytic performance of Co-Ce catalysts towards N2O decomposition

The catalytic decomposition of nitrous oxide (N₂O) is an effective and feasible way for mitigating greenhouse gas emissions and reducing stratospheric-ozone-depleting. In this work, Co-Ce-X (X = 7.0, 7.5, 8.0, 8.5, and 9.5, referring to the precipitation pH) composite oxide catalysts were prepared by co-precipitation method by adjusting the pH values and evaluated their catalytic performance for N₂O decomposition. Interestingly, the volcano-type relationship between catalytic activity and precipitation pH over Co-Ce-X catalysts can be observed. The best-performing of Co-Ce-8.0 catalyst achieved the full N₂O conversion at only 380 °C, which was much lower than that of other catalysts. The superior catalytic performance of Co-Ce-8.0 derived from the abundant oxygen vacancies and Co²⁺ content, which both contributed to the activation of N₂O, the desorption of oxygen species, thereby synergistically promoted the reaction cycle. Mechanism studies showed that the formation of undesirable nitrogen-containing intermediates on Co-Ce-8.0 was minimal, indicating that N₂O adsorbed on the catalyst tended to undergo decomposition reactions. Furthermore, Co-Ce-8.0 also exhibited the excellent catalytic stability with almost no deactivation within 50 h. This work emphasized the significance of basic parameters in the process of catalyst preparation on the catalytic performance, and provided guidance for designing other high-efficiency N₂O decomposition catalysts.