Highly efficient nitrogen-doped porous carbon supported single atom catalysts for CO₂ reduction

Nitrogen-coordinated single metal atoms supported on carbon (M-N_x/C) catalysts show exceptional activities in the electrochemical CO₂ reduction reaction (CO₂RR). However, investigating the relationship between the support properties, such as morphology and electron conductivity, and catalytic activity remains challenging because conventional high-temperature pyrolysis induces multiple M-N_x coordination in the M-N_x/C catalysts.

In this study, we fabricated a series of nitrogen-doped porous carbon supports with varying pore sizes and degrees of graphitization, and subsequently introduced Ni-N₄ active sites by anchoring Ni phthalocyanine (NiPc). We found that the electron conductivity of the support is crucial for enhancing the CO selectivity in the low-potential region (from –0.5 to –0.7 V_RHE). However, effective CO₂ transport, which is strongly affected by the morphology of the support, has a more dominant effect than electron conductivity on catalytic activity. The optimized catalyst demonstrates outstanding CO₂RR performances owing to the presence of mesoporous graphitic carbon and nitrogen in the supports.