CO2 conversion over Cu–Mo2C catalysts: effect of the Cu promoter and preparation method

Abstract

Mo₂C-Based catalysts constitute a promising class of materials for CO₂ hydrogenation to high added-value products. In this work, we show that methanol formation can be significantly enhanced by the addition of Cu. Moreover, the preparation method of the Cu–Mo₂C catalysts can significantly affect the catalytic performance. Synthesis via the sol–gel auto-combustion route leads not only to the most active material, achieving 30 mol% CO₂ conversion at 325 °C and 45 bar, but also to the most selective towards methanol (∼50 C-mol% at 5 mol% conversion). This performance is slightly inferior for the catalyst prepared with the solvothermal method. Conversely, the catalyst synthesized with the solid state route presents by a long way the worst activity and selectivity in the reaction. We show with spectroscopy and temperature programed studies that Cu addition and the synthesis method modify the population, type and strength of the sites available for CO₂ and H₂ activation on the surface and hence the catalytic performance. The results suggest that strong interaction between the Cu and Mo₂C phases and formation of Mo₂C–Cu⁺ interfaces are required for the efficient hydrogenation of CO₂ to methanol.