In situ characterization techniques for thermocatalytic CO2 hydrogenation

Abstract Direct hydrogenation of CO2 with renewable H2 into value-added chemicals provides a promising pathway for sustainable carbon utilization in the future. Although extensive research has been conducted on CO2 hydrogenation, the complexity of heterogeneous catalysis under operational conditions continues to pose challenges in identifying active sites and elucidating corresponding reaction mechanisms. Conventional ex situ characterization techniques often fail to capture the dynamic structural evolution and short-lived intermediates during the reaction, thereby hindering the establishment of reliable structure-activity relationships and the identification of reaction pathways. As a result, the application of in situ characterization methods is essential for correlating catalyst structure with catalytic performance, and for uncovering mechanistic details under realistic reaction conditions. In this context, this review summarizes recent advances in the application of various in situ characterization techniques in thermocatalytic CO2 hydrogenation, emphasizing their role in identifying active centers, detecting key intermediates, and clarifying underlying reaction pathways. Furthermore, it discusses current challenges and offers perspectives on future directions for in situ characterizations in revealing the active centers and reaction networks of CO2 hydrogenation.