Facet-Controlled Cu-doped and K-promoted Fe2O3 nanosheets for efficient CO2 hydrogenation to liquid hydrocarbons

Abstract

Hydrogenation of CO2 into liquid hydrocarbons is an attractive route for chemical utilization of CO2, but suffers from limited product selectivity. By controlling the exposed surface atoms of metal catalyst, purposefully enhancing the reaction rate of bottleneck steps for CO2 activation and C-C coupling is expected to solve this problem. Here, we tuned the exposed surface atoms of catalysts separately and simultaneously by facet control, doping and promoter modification; a nanosheet-shaped Fe2O3 rich in oxygen vacancies was first constructed to enhance the adsorption and activation of CO2. Cu doping and K promoter were further used to promote the formation of active χ-Fe5C2 phase and facilitate the coupling of C-C bond to form long chain fuels. The optimized K-promoted and Cu-doped Fe2O3 nanosheets (3 K/6Cu-Fe-S) exhibited high CO2 conversion (46.5%) and C5+ hydrocarbons selectivity (53.6%), accompanied with low CO (5.3%) and CH4 selectivity (12.2%) at 300 °C, outperforming other reported Fe-based catalysts significantly. Meanwhile, a 205 h on stream test indicated the excellent stability of 3 K/6Cu-Fe-S. The effects of each tuning method on catalytic activity and product selectivity were further studied by combining the change of the phase and surface electronic structure of the catalyst before and after the reaction. Cu doping and K promoter were verified to have a synergistic enhancement effect on the hydrogenation performance of CO2, rather than just the sum of the two. These findings would be beneficial for the rational design of CO2 hydrogenation catalysts.