Effects of self-reduction of Co nanoparticles on mesoporous graphitic carbon-nitride to CO hydrogenation activity to hydrocarbons

Thermal aggregations of Co nanoparticles have been known to be the main reason for catalyst deactivations for CO hydrogenation to hydrocarbons. Self-reduction effects of the supported Co nanoparticles on the ordered mesoporous graphitic carbon nitride (g-C₃N₄) with the help of functional groups of the reductive g-C₃N₄ revealed an unprecedented resistance to thermal aggregations of Co nanoparticles. The mesoporous g-C₃N₄ with abundant nitrogen-containing functional groups facilitated an easy reduction of cobalt oxides without any significant aggregation. By comparing with the mesoporous carbon support (CMK-3), the Co-supported g-C₃N₄ revealed a higher activity and C₅₊ selectivity due to the robust preservation of smaller metallic Co nanoparticles with their average sizes of ~2 nm even after the reaction. The nitrogen-containing functional groups of the g-C₃N₄ accelerated the reduction of Co₃O₄ to metallic Co as well as prevented its aggregations. The relatively inactive cobalt carbide (Co₂C) phases formed on the reference Co-supported CMK-3 were effectively prohibited while using the reductive g-C₃N₄ support, which seems to be new alternative catalytic system without any aggregation-free reduction treatment.