Synthesis of Fe-CNFs and Mechanistic Insights into Carbon-Water Reaction

Iron-based carbon nanofibers (Fe-CNFs) have garnered significant attention due to their promising applications as functional materials or precursors in the field of catalysis, energy storage, and electromagnetic interference shielding. In this work, electrospun Fe₃O₄-CNFs were reduced under a H₂/Ar atmosphere to obtain Fe-CNFs, and the reduction temperature and holding time were systematically optimized. Notably, a pronounced carbon gasification phenomenon was observed at elevated temperatures (>550 °C), leading to a complete consumption of the carbon matrix. The underlying mechanism was explored using temperature-programmed reduction with mass spectrometry (TPR-MS) and density functional theory (DFT) calculations. The results suggest that the carbon gasification during the H₂ reduction process is primarily driven by the carbon-water reaction, which can be catalyzed by the in situ-formed Fe nanoparticles. As the temperature increases, various reactions-including hydrogen dissociation, H₂ spillover, carbon-water reaction, and Boudouard reaction-may progressively consume the carbon framework, ultimately leading to structural collapse and complete material loss. This study elucidates the underlying mechanism of carbon-water reaction and provides practical guidance for the optimization of synthesis parameters, thereby enhancing the yield and structural integrity of free-standing Fe-CNFs for their application in catalysis and energy storage-related fields.