Direct hydrogenation of CO₂ to liquid hydrocarbons over K/Fe-C catalysts: Effect of porous carbon matrix and K modification

Direct hydrogenation of CO₂ to liquid hydrocarbons via modified Fischer-Tropsch synthesis represents an appealing and sustainable route for efficient CO₂ utilization. However, the selective production of liquid hydrocarbons remains a significant challenge. In this work, we designed a series of carbon-coated K/Fe-C catalysts with various K loadings (ranging from 0 to 8 wt%) that enhance C₅₊ hydrocarbon selectivity during CO₂ hydrogenation. It is found that the 4 K/Fe-C catalyst exhibits the highest C₅₊ selectivity of 54.78 % at CO₂ conversion of 32.40 % and good stability within 100 h time-on-stream. This is attributed to the high dispersion of the Fe nanoparticles and the confinement effect of porous carbon matrix on the aggregation of Fe nanoparticles, resulting in high catalytic activity and selectivity. Meanwhile, the well dispersed K on the porous carbon matrix can reduce the particle size of Fe nanoparticles and promote the production of iron carbide active species for CO₂-FTS, thus facilitating the selective formation of C₅₊ hydrocarbons. Moreover, we also discussed a possible reaction mechanism for the direct hydrogenation of CO₂ to C₅₊ hydrocarbons over the K/Fe-C catalysts. This study provides deep insights into the design of efficient Fe-C catalysts for converting CO₂ to liquid hydrocarbons.