Direct CO2 hydrogenation to ethanol over supported Co2C catalysts: Studies on support effects and mechanism

Direct CO2 hydrogenation to ethanol is one of the promising and emerging routes for the transformation of CO2 into value-added chemicals, but it remains a major challenge because of low ethanol selectivity and catalytic stability. In this work, Na-promoted cobalt catalysts supported on different materials (Al2O3, ZnO, AC, TiO2, SiO2, and Si3N4) were evaluated to elucidate the effects of supports. The SiO2-and Si3N4-supported catalysts exhibited efficient generation of ethanol with 18% CO2 conversion and 62% selectivity in the alcohol distribution at 250 degrees C, whereas CH4 was predominantly produced on other supported catalysts. Characterization results indicated that the Co2C active phase only remained intact on SiO2 and Si3N4 supports during reaction and exhibited excellent durability for 300 h, which was attributed to the existence of a strong metal-support interaction (SMSI) obtained by Si-O-Co bond formation. In situ DRIFTS results revealed that CO produced on Co2C inserted into CHx intermediates to form ethanol. Moreover, CO as the reactive intermediate could induce the regeneration and reconstruction of decomposed Co2C on the surface for catalytic sustainability. (C) 2019 Elsevier Inc. All rights reserved.