Cobalt-nitrogen-carbon sites on carbon aerogels for enhanced electrocatalytic CO2 activity

Constructing Co-NxC sites on three-dimensional mesopore and macropore-rich carbon aerogels (CoPc@N-CA-500) through the typical polycondensation coupling pyrolysis (500 ℃) strategy was developed for optimizing the microenvironment of active sites to improve the accessibility of active sites and CO2 molecule, enhancing the selectivity and activity of CO2RR, where CoPc@N-CA-500 achieved a carbon monoxide Faradaic efficiency (FECO) of 92.48% and partial CO current density of 21.72 mA cm−2 at −0.80 V vs. RHE, and a rechargeable zinc–CO2 battery with a maximal power density of 0.69mW cm−2. [Display omitted] •CoPc was fixed on 3D porous N-doped carbon aerogel (N-CA) by pyrolysis to form CoPc@N-CA-500.•The porous carbon network facilitates Co-NxC active sites exposure and CO2 activation kinetic.•The maximal FECO of 92.48%, jCO of 21.72 mA cm−2, and TOFCO of 1.23 s−1 were obtained in H-cell.•CoPc@N-CA-500-based Zn–CO2 battery achieved the peak power density of 0.69 mW cm−2. Developing highly-efficient electrocatalysts with metal-nitrogen-carbon (M−NxC) sites for electrochemical CO2 reduction reaction (CO2RR) towards carbon monoxide (CO) is an effective way towards carbon neutralization. Herein, nitrogen-doped carbon aerogels (N-CA) supported Co-NxC sites with cobalt phthalocyanine (CoPc) as precursor via pyrolysis (500 ℃) strategy is reported. The CoPc@N-CA-500 catalyst with the average pore size of 8.57 nm, displays a wide potential window from −0.5 to −0.9 V vs. RHE with the CO Faradaic efficiency (FECO) over 80%. It also exhibits the maximal FECO of 92.48%, the CO partial current density of 21.72 mA cm−2, CO turnover frequency (TOFCO) of 1.23 s−1 and stability over 20 h (under −0.8 V vs. RHE), which is significantly higher than that of CoPc@CB-500 (53.91%, 4.47 mA cm−2, 0.14 s−1) with the average pore size of 2.54 nm, while selecting commercial carbon black (CB) as the carrier. The superior activity of CoPc@N-CA-500 could be attributed to its unique porous system, which not only promotes the mass transfer of CO2 molecules to facilitate the CO2RR kinetic, but is beneficial to expose Co active sites. Meanwhile, a home-made zinc-CO2 battery with CoPc@N-CA-500 as cathode achieved a peak power density of 0.69 mW cm−2 and maximum FECO of 87.41%.