Decoupling the Interfacial Catalysis of CeO<sub>2</sub>-Supported Rh Catalysts Tuned by CeO<sub>2</sub> Morphology and Rh Particle Size in CO<sub>2</sub> Hydrogenation
Weiqi Liao, Minnan Yue, Junyi Chen, Ziwei Wang, Jieqiong Ding, Yuxing Xu, Yu Bai, Xiaochun Liu, Aiping Jia, Weixin Huang, Zhenhua Zhang
Abstract
Metal–oxide interfaces play a crucial role in catalyzing CO 2 conversion, while comprehensively decoupling interfacial catalysis is challenging due to their structural complexity. Herein, Rh/CeO 2 catalysts, whose interfacial structures are finely tuned by altering the CeO 2 morphologies and Rh particle sizes, were employed for CO 2 hydrogenation. The results reveal that the density of interfacial oxygen vacancies that varies with the CeO 2 morphologies determines the catalytic activity, while the product selectivity strongly depends on the nature of supported Rh species. With a decrease in Rh particle size, the weakened metallicity results in the suppression of the Sabatier reaction and thus the low CH 4 selectivity. Meanwhile, the enhanced reverse water–gas shift process that is more easily catalyzed than the Sabatier reaction contributes to the promotion of catalytic CO 2 efficiency. Interestingly, the CH 4 selectivity increases with the reaction temperature rise at fine Rh particles, which could be ascribed to the enhanced H-spillover effect at high temperatures. Spectroscopic results confirm CO 2 hydrogenation proceeding through a redox mechanism to generate an adsorbed CO intermediate that either is further hydrogenated into CH 4 with strong CO adsorption capacity/H-spillover effect or desorbs directly into CO.