Research progress in pure-phase iron carbides for COx hydrogenation.

COx hydrogenation is a pivotal technological route for efficiently converting non-petroleum carbon resources into fuels and value-added chemicals. Owing to their low cost and excellent catalytic activity, iron-based catalysts are highly preferred for these processes, with iron carbides widely recognized as the key active phases in both Fischer-Tropsch synthesis (FTS) and CO2 hydrogenation. However, in conventional iron-based catalysts, iron carbides typically exist as multiphase mixtures, and their complex dynamic evolution under reaction conditions obscures the intrinsic catalytic roles of specific iron carbide phases. Recently, advances in the controllable synthesis of pure-phase iron carbides have revealed their remarkable catalytic potential in COx hydrogenation reactions, providing important model systems to eliminate multiphase interference and precisely elucidate structure-activity relationships. This review summarizes the structural characteristics, synthesis methods, and stabilization strategies of pure-phase iron carbides, alongside their recent applications in COx hydrogenation reactions. Particular emphasis is placed on the advantages of pure-phase structures in suppressing CO2 selectivity (in FTS) while enhancing the selectivity toward target hydrocarbons. This work aims to provide insights and guidance for the development of efficient, stable, and carbon-efficient iron-based catalysts.