Zn-Nx Doping in Carbon Nanotubes Boosts Selective CO2 Electroreduction to CO

Electroreduction of CO2 to CO is attractive target to store energy from intermittent sources, as it requires the transfer of only two electrons and two protons. Metal-based catalysts (Au, Ag, Ni, Fe, etc.), especially metal- and N-co-doped carbon materials have been proven to show high selectivity for CO production. However, for Zn-based catalysts, the critical active site is still intensely debated. Herein, we synthesize a series of carbon nanotube-supported Zn-based catalysts with a tunable ratio of isolated ZnNx sites and Zn-based nanoparticles. We identify ZnNx moieties anchored on the surface of carbon nanotubes are catalytically highly active for the selective CO2 electroreduction to CO, with the Faradaic efficiency (FE) as high as 97.3 %. In contrast, N-doped carbon nanotubes (NCNTs) and Zn-containing nanoparticles supported on NCNTs exhibit inferior selectivity with the CO FEs of 56.7 % and 72.9 %, respectively, suggesting that Zn doping in carbon and the existing forms are of significant importance for improving the ability of Zn-based catalysts for electrocatalytic reduction of CO2.

Automated summary

The synthesis of carbon nanotube-supported Zn-based catalysts with anchored ZnNx moieties on the surface of carbon nanotubes showed high catalytic activity for the selective electroreduction of CO2 to CO, with a Faradaic efficiency as high as 97.3%. In comparison, N-doped carbon nanotubes and Zn-containing nanoparticles supported on carbon nanotubes exhibited lower selectivity, with CO FEs of 56.7% and 72.9%, respectively, highlighting the importance of Zn doping in carbon and its existing forms for improving the electrocatalytic ability of Zn-based catalysts for CO2 reduction.