Hydrophobic interfaces regulate iron carbide phases and catalytic performance of FeZnOx nanoparticles for Fischer-Tropsch to olefins

Fischer-Tropsch to olefins (FTO) with controllable iron carbide phase and high carbon utilization efficiency for Fe-based nanocatalyst attracts great interest but remains challenge. Herein, we report that the metastable Fe7C3 phase can be effectively tailored by altering shell thickness of hydrophobic SiO2 over a core-shell nanostructured FeZn@SiO2-c nanocatalyst. χ-Fe5C2 was the dominated iron carbide phase for FeZnOx and FeZn@SiO2 nanocatalysts, while numerous Fe7C3 phases existed for hydrophobic FeZn@SiO2-c nanospheres. Compared with FeZnOx, the CO2 selectivity of FeZn@ 4.1-SiO2-c decreased by > 70%, while 1.7-fold higher olefins selectivity was simultaneously obtained during syngas conversion process. The hydrophobic interface greatly suppressed the water-gas-shift reaction by promoting the quick diffusion of water, and the as-formed H2-lean and CO-rich local chemical environment benefits the formation of Fe7C3 and olefins products. This work provides a promising strategy to design phase-stable Fe7C3 with improvement of carbon efficiency for Fe-based nanocatalysts.