Hierarchical Carbon Nanocage-Enabled Electron Buffering to Indium Oxide for Efficient CO₂ Hydrogenation to Methanol

The hydrogenation of CO 2 to methanol over In 2 O 3 -based catalysts is highly sensitive to the concentration of surface oxygen vacancies (O v ). While increasing the O v concentration can enhance the catalytic performance, it also increases the risk of over-reduction during CO 2 hydrogenation, leading to a trade-off between activity and stability. Here, we demonstrate that hierarchical carbon nanocages (hCNCs) act as effective “electron buffering agents” for In 2 O 3, mitigating this trade-off and thereby enhancing the methanol yield, with nitrogen doping of hCNCs further amplifying this effect. Detailed investigations reveal that hCNCs donate electrons to O v -deficient In 2 O 3 to promote O v formation, while also extracting electrons from O v -rich In 2 O 3– x, preventing over-reduction to metallic In. As a result, In 2 O 3 supported on hCNCs maintains a consistently high O v concentration, enhancing both the catalytic activity and stability. This work highlights the promising potential of hCNCs in the hydrogenation of CO 2 to methanol and stimulates interest in their exploitation for other redox catalytic processes.