Efficient inverse cobalt-based catalysts for low-temperature methanation of low-concentration CO2 streams

The catalytic hydrogenation of residual carbon dioxide in hydrogen-rich gas streams is highly relevant to hydrogen purification and low-carbon energy technologies. Herein, we report a series of cobalt-based inverse Ba–REE/Co (REE = Ce, Nd, Sm) catalysts designed for efficient methanation of low-concentration CO 2 streams. The application of an inverse oxide/metal configuration resulted in promoter oxides being dispersed on metallic cobalt, thereby maximizing metal–oxide interfacial interactions and enabling synergistic reactant activation. All catalysts exhibited high activity, achieving 78–84% CO 2 conversion at 220 °C and nearly complete conversion at 270 °C. Among the catalysts, Ba–Ce/Co showed the best performance. Comprehensive characterization studies revealed that catalytic performance is not directly dependent on CO 2 adsorption capacity but rather on the nature and accessibility of adsorption sites under reaction conditions. In particular, weak, accessible basic sites promote efficient CO 2 activation and intermediate turnover, whereas stronger binding leads to partial surface blocking. The findings also highlight inverse oxide/metal architectures as a rational design strategy for highly efficient catalysts for processes of industrial and economic significance.