Stabilizing Co2C with H2O and K promoter for CO2 hydrogenation to C2+hydrocarbons

The decomposition of cobalt carbide (Co2C) to metallic cobalt in CO2 hydrogenation results in a notable drop in the selectivity of valued C2+ products, and the stabilization of Co2C remains a grand challenge. Here, we report an in situ synthesized K-Co2C catalyst, and the selectivity of C2+ hydrocarbons in CO2 hydrogenation achieves 67.3% at 300 & DEG;C, 3.0 MPa. Experimental and theoretical results elucidate that CoO transforms to Co2C in the reaction, while the stabilization of Co2C is dependent on the reaction atmosphere and the K promoter. During the carburization, the K promoter and H2O jointly assist in the formation of surface C* species via the carboxylate intermediate, while the adsorption of C* on CoO is enhanced by the K promoter. The lifetime of the K-Co2C is further prolonged from 35 hours to over 200 hours by co-feeding H2O. This work provides a fundamental understanding toward the role of H2O in Co2C chemistry, as well as the potential of extending its application in other reactions.

Automated summary

In this study, an in situ synthesized K-Co2C catalyst was developed for CO2 hydrogenation, achieving a selectivity of 67.3% for C2+ hydrocarbons. Experimental and theoretical results showed that CoO transformed into Co2C, and the stability of Co2C depended on the reaction atmosphere and the K promoter. The formation of surface C* species was facilitated by the co-action of K promoter and H2O, while the adsorption of C* on CoO was enhanced by the K promoter. The addition of H2O extended the lifetime of K-Co2C from 35 hours to over 200 hours.