Cost‐Effective Synthesis of Fe5C2 Catalyst From Nanosized Zero‐Valent Iron to Achieve Efficient Photothermocatalytic CO Hydrogenation to Light Olefins

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AbstractFe‐based catalysts are commonly applied in the process of Fischer−Tropsch synthesis (FTS) to olefins, with Hägg iron carbide (Fe5C2) recognized as the primary active phase. However, iron carbonyls, the raw materials for wet chemical synthesis of Fe5C2, are expensive and toxic, which limits large‐scale preparation. Here, a cost‐effective and versatile method is proposed for the synthesis of Fe5C2 nanoparticles (NPs) with nanosized zero‐valent iron (abbreviated as NZVI, prepared by reducing iron salts or ball‐milling iron powder) instead of iron carbonyls, achieving a cost reduction of 76.8%. Experimental characterizations revealed that NZVI obtained from the reduction of iron salts can catalyze the cracking of octadecylamine to form a carbonized atmosphere, thus realizing the phase transition of Fe into Fe5C2. The optimized Fe5C2 catalyst is employed in the photothermocatalytic FTS process, achieving a light olefins selectivity of 54.2% in hydrocarbons, with a CO conversion of 24.3%. Furthermore, it is proved that the particle size and surface oxide state of NZVI can impact the synthesis of Fe5C2. This study demonstrates a cost‐effective method for the large‐scale preparation of the Fe5C2 catalyst.