Stabilizing Co <sub>2</sub> C with H <sub>2</sub> O and K promoter for CO <sub>2</sub> hydrogenation to C <sub>2+</sub> hydrocarbons
Mingrui Wang, Peng Wang, Guanghui Zhang, Zening Cheng, Mengmeng Zhang, Yulong Liu, Rongtan Li, Jie Zhu, Jianyang Wang, Kai Bian, Yi Liu, Fanshu Ding, Thomas P. Senftle, Xiaowa Nie, Qiang Fu, Chunshan Song, Xinwen Guo
Abstract
The decomposition of cobalt carbide (Co 2 C) to metallic cobalt in CO 2 hydrogenation results in a notable drop in the selectivity of valued C 2+ products, and the stabilization of Co 2 C remains a grand challenge. Here, we report an in situ synthesized K-Co 2 C catalyst, and the selectivity of C 2+ hydrocarbons in CO 2 hydrogenation achieves 67.3% at 300°C, 3.0 MPa. Experimental and theoretical results elucidate that CoO transforms to Co 2 C in the reaction, while the stabilization of Co 2 C is dependent on the reaction atmosphere and the K promoter. During the carburization, the K promoter and H 2 O 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-Co 2 C is further prolonged from 35 hours to over 200 hours by co-feeding H 2 O. This work provides a fundamental understanding toward the role of H 2 O in Co 2 C chemistry, as well as the potential of extending its application in other reactions.