Unveiling the Active Site of Metal-Free Nitrogen-doped Carbon for Electrocatalytic Carbon Dioxide Reduction

Nitrogen-doped (N-doped) carbon materials have been widely studied for electrocatalytic CO2R to CO. However, the active sites in N-doped carbon remain under debate owing to the complication in N types and the challenge in controllable synthesis. Here, via an innovative approach of template-assisted pyrolysis of phthalocyanine, we achieve a controlled preparation of N types in N-doped carbon foams. Electrochemical experiments show that the catalyst dominated by graphitic N rather than other N types drives highly selective CO2R to CO against the hydrogen evolution reaction, which achieves a CO Faradaic efficiency of 95% at 0.5 V versus RHE and runs stably for 80 h. Theoretical calculations indicate that carbon atoms next to graphitic N are triggered for the CO production, while carbon atoms next to pyridinic N promote the hydrogen evolution and pyrrolic N disfavors both reactions.