Unveiling the Filter Effect of CaCO₃ Hydrogenation in Integrated CO₂ Capture and Methanation

CO₂ methanation represents a promising carbon mitigation approach, but conventional CO₂ hydrogenation struggles to maintain high CH₄ selectivity over a wide temperature range. Through comparative studies of CO₂ hydrogenation and CaCO₃ hydrogenation, we discovered that CaCO₃ hydrogenation achieves sustained high CH₄ selectivity over a broad temperature range. We propose a hydrogen spillover-driven HCOO* pathway for CaCO₃ conversion, revealed by combined in situ characterization and DFT calculations. Compared to the HCOO* intermediate generated in CO₂ hydrogenation, the HCOO* species derived from CaCO₃ hydrogenation exhibits superior stability, effectively suppressing CO* formation. This mechanism demonstrates universal applicability: various CO₂ hydrogenation catalysts consistently achieve >95% CH₄ selectivity during CaCO₃ conversion, regardless of their initial CO₂ hydrogenation performance. Systematic evaluation identifies hydrogen spillover intensity as the key parameter governing catalytic CaCO₃ hydrogenation performance, with stronger spillover capacity leading to higher conversion efficiency. The revealed selectivity polarization effect establishes new catalyst design principles for efficient integrated carbon capture and utilization processes.