Tuning the interaction between Na and Co2C to promote selective CO2 hydrogenation to ethanol

[Display omitted] •The interaction between Co2C and alkali metals was formed and modulated.•Enhancing the interaction of Na with Co2C could form stable NaCo2C active sites.•The dispersion and particle size of Co2C were affected by the interaction.•The CO/CHx ratio on NaCo2C (111) surface could be tuned by the interaction.•The optimal ethanol STY was obtained under the moderate interaction. Direct CO2 hydrogenation to ethanol is one of the promising alternatives to realize “carbon-neutral” protocol. However, stabilizing catalyst structure and modulating CO activation remain challenging. Herein, we obtained stable NaCo2C active sites by tuning the interaction between Na and Co species. Enhancing the interaction of Na with Co2C through forming NaCo bond induced the dispersion of Co2C and the reduction of particle size, evidently improving RWGS reaction rate and ethanol space time yield (STY). In situ adsorption experiments and density functional theory (DFT) calculations demonstrated that the amount of CO2 and CO adsorption was increased with the increase of the interaction, while CO dissociative activation on NaCo2C (111) surface was inhibited, thereby regulating the surface CO/CHx ratio and facilitating subsequent CO coupling to synthesize ethanol. Excessive interaction weakened the strength of CO adsorption resulting in higher CO selectivity. The moderate interaction was obtained at 2 wt% Na and the ethanol STY reached as high as 1.1 mmol g−1 h-1 (C2+OH/ROH fraction of 91.3 %), which is 10 times higher than that without Na. This work brings an enabling strategy to tune reaction processes and design stable and efficient catalysts.