Rational Synthesis of Iron Carbide Nanocatalysts for Fischer–Tropsch Synthesis: The Role of Carbon Chemical Potential

作者：Zhenqiang Ma, Yi Cai, Yueyue Jiao, Xingwu Liu, Jinjia Liu, Wenping Guo, Xingchen Liu, Yongwang Li, Xiaodong Wen · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c11223 · 被引用次数：11 · 研究领域：Catalysts for Methane Reforming、Subcritical and Supercritical Water Processes、Iron and Steelmaking Processes

Understanding nanoparticle phase behavior under reactive conditions is critical for rational catalyst design in sustainable energy technologies. Yet, the phase transformations of multielement catalytic solids remain poorly understood, particularly when accompanied by compositional changes in reactive environments. Using iron carbide (Fe x C y ) as a model system, we investigate size-dependent phase stability and transformation kinetics across various chemical environments relevant to Fischer–Tropsch synthesis. By integrating nanoscale thermodynamics and kinetics into a unified theoretical framework, we construct comprehensive phase diagrams that explain the anomalous predominance of the χ -Fe 5 C 2 phase and the rarity of the Fe 7 C 3 phase─a longstanding puzzle in heterogeneous catalysis. Located at the intersection of all other phase stability regions across a broad range of carbon chemical potentials and particle sizes, χ -Fe 5 C 2 functions as a central hub, facilitating transitions among various iron carbide phases, and has relatively low formation kinetic barriers from neighboring phases. In contrast, Fe 7 C 3 is thermodynamically stable and kinetically favorable only within a very narrow range (approximately 0.03 eV) of carbon chemical potential at relatively large particle sizes. Our theoretical predictions, rigorously validated through precisely designed phase transformation experiments, reveal how nanoscale effects fundamentally govern phase selectivity and transfor...