Co-Fe Clusters Supported on N-Doped Graphitic Carbon as Highly Selective Catalysts for Reverse Water Gas Shift Reaction

Graphitic carbons are suitable supports of metal nanoparticles with catalytic activity. In the present study, the preparation of N-doped graphitic carbon supporting clusters of Fe-Co alloys starting from biomass waste is reported. These sub-nanometric Co-Fe clusters supported on N-doped graphitic carbon at a metal loading below 0.2 wt % exhibit high activity for the selective hydrogenation of CO2 to CO. Operating at 500 degrees C and 10 bar with an H-2/CO2 molar ratio of 7 and a space velocity of 600 h(-1), a conversion of 56% with a selectivity of over 98% to CO, and remarkable stability over 30 h operation was obtained. Interestingly, analogous catalysts based on N-doped graphitic carbon with much higher Co-Fe loadings and an average particle size range of 1-5 nm exhibit only half of this activity, with similar CO selectivity. This contrasting behavior reveals the dramatic effect of the particle size on the catalytic activity. In comparison, SiO2 as support under similar conditions affords CH4 as the main product.