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

Direct CO 2 hydrogenation to ethanol is one of the promising and emerging routes for the transformation of CO 2 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 (Al 2 O 3 , ZnO, AC, TiO 2 , SiO 2 , and Si 3 N 4 ) were evaluated to elucidate the effects of supports. The SiO 2 - and Si 3 N 4 -supported catalysts exhibited efficient generation of ethanol with 18% CO 2 conversion and 62% selectivity in the alcohol distribution at 250 °C, whereas CH 4 was predominantly produced on other supported catalysts. Characterization results indicated that the Co 2 C active phase only remained intact on SiO 2 and Si 3 N 4 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[sbnd]O[sbnd]Co bond formation. In situ DRIFTS results revealed that CO produced on Co 2 C inserted into CH x intermediates to form ethanol. Moreover, CO as the reactive intermediate could induce the regeneration and reconstruction of decomposed Co 2 C on the surface for catalytic sustainability. © 2019 Elsevier Inc.