Unveiling the Filter Effect of CaCO ₃ Hydrogenation in Integrated CO ₂ Capture and Methanation

ABSTRACT CO ₂ methanation represents a promising carbon mitigation approach, but conventional CO ₂ hydrogenation struggles to maintain high CH ₄ selectivity over a wide temperature range. Through comparative studies of CO ₂ hydrogenation and CaCO ₃ hydrogenation, we discovered that CaCO ₃ hydrogenation achieves sustained high CH ₄ selectivity over a broad temperature range. We propose a hydrogen spillover‐driven HCOO* pathway for CaCO ₃ conversion, revealed by combined in situ characterization and DFT calculations. Compared to the HCOO* intermediate generated in CO ₂ hydrogenation, the HCOO* species derived from CaCO ₃ hydrogenation exhibits superior stability, effectively suppressing CO* formation. This mechanism demonstrates universal applicability: various CO ₂ hydrogenation catalysts consistently achieve >95% CH ₄ selectivity during CaCO ₃ conversion, regardless of their initial CO ₂ hydrogenation performance. Systematic evaluation identifies hydrogen spillover intensity as the key parameter governing catalytic CaCO ₃ 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.