An Overview on Dynamic Phase Transformation and Surface Reconstruction of Iron Catalysts for Catalytic Hydrogenation of COx for Hydrocarbons

Catalytic hydrogenation of COx (CO and CO2) with renewable H2 represents a feasible practice for carbon capture and utilization and synthesis of chemical commodities, such as olefins, aromatics, and higher alcohols as well as liquid fuels. Direct synthesis via Fischer–Tropsch Synthesis (FTS) is considered as one of the most promising processes. Iron-based catalysts have been recognized as efficient candidates for catalytic hydrogenation of both CO and CO2 to value-added hydrocarbons due to their superior activities for C–O bond dissociative activation, reverse/water gas shift reaction, and C–C chain growth. The structural complexity and dynamic evolution of iron-based catalysts under COx-FTS conditions impose challenges on the understanding of the reaction mechanisms, the dynamic structure of active sites and further improvements of the catalytic performance. In this Review, we discussed the recent developments in characterization techniques for identifying the structural evolution of iron-based catalysts under reaction conditions. We also summarized feasible strategies to manipulate the process of the structural change via promoter interfacing, catalyst pretreating protocols, and application of external physical fields. Finally, we concluded the review by identifying current challenges and opportunities for the next generation of COx catalytic hydrogenation process with an emphasis on the combinatorial contributions from in situ/operando characterizations, chemometrics and machine learning.