Identifying and enhancing the spillover of crucial intermediates on the Fischer–Tropsch catalyst: A mechanistic approach

Abstract

Understanding and enhancing spillover phenomena in Fischer–Tropsch Synthesis (FTS) is critical for optimizing catalyst performance. In this study, we present a comprehensive evaluation of hydrogen, carbon monoxide, and water (θ-H, θ-CO, and θ-H₂O) spillover mechanisms over a series of engineered multi-shell nanocomposite catalysts: Co@C(Z-d)@SiO₂@CeO₂ (NC), the etched NC (NCE), and the Ru-doped NCE (RNCE). A suite of advanced characterization techniques, XRD, HR-XPS, FTIR, Raman, UV–Vis DRS, and TPD, along with molecular dynamics (MD) simulations, was employed to elucidate structure–function relationships and quantify the spillover behavior of key FTS intermediates. Our findings reveal that etching the silica layer significantly enhances oxygen vacancy formation and overall spillover activity. Among all catalysts, RNCE exhibits the highest oxygen vacancy concentration, the lowest oxygen vacancy formation energy, and the narrowest band gap, attributes that contribute to its superior spillover capacity. MD simulation results confirm that θ-H₂O and θ-CO spillovers dominate over hydroxyl and θ-HCO spillovers, with RNCE achieving the highest spillover rates across all intermediate species. Performance tests conducted under varying partial pressures of H₂, CO, and H₂O further validate that enhanced spillover correlates directly with increased CO conversion and C₅⁺ hydrocarbon selectivity. This study not only deciphers the mechanistic role of spillover in FTS but also highlights the synergistic effects of Ru promotion, silica etching, and oxygen vacancy engineering in advancing the design of high-performance FTS catalysts for efficient hydrocarbon production.