Molecular Evidence for Metallic Cobalt Boosting CO2 Electroreduction on Pyridinic Nitrogen.

Nitrogen-doped carbon materials (N-Cmat ) are emerging as low-cost metal-free electrocatalysts for the electrochemical CO2 reduction reaction (CO2 RR), although the activities are still unsatisfactory and the genuine active site is still under debate. We demonstrate that the CO2 RR to CO preferentially takes place on pyridinic N rather than pyrrolic N using phthalocyanine (Pc) and porphyrin with well-defined N-Cmat configurations as molecular model catalysts. Systematic experiments and theoretic calculations further reveal that the CO2 RR performance on pyridinic N can be significantly boosted by electronic modulation from in-situ-generated metallic Co nanoparticles. By introducing Co nanoparticles, Co@Pc/C can achieve a Faradaic efficiency of 84 % and CO current density of 28 mA cm-2 at -0.9 V, which are 18 and 47 times higher than Pc/C without Co, respectively. These findings provide new insights into the CO2 RR on N-Cmat , which may guide the exploration of cost-effective electrocatalysts for efficient CO2 reduction.