Rational design of nitrogen-doped porous carbon support on single atom catalysts for efficient CO2 electroreduction

Abstract

Nitrogen-coordinated single metal atoms supported on carbon (M–N_x/C) catalysts exhibit remarkable activities during the electrochemical CO₂ reduction reaction (CO₂RR). However, exploring 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. Herein, a series of nitrogen-doped porous carbon supports with various pore sizes and degrees of graphitization were prepared, and Ni–N₄ active sites were subsequently loaded 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 exhibits outstanding CO₂RR performances owing to the presence of mesoporous graphitic carbon and nitrogen in the supports, compared with 2D graphene without mesopores and mesoporous graphitic carbon supports without nitrogen.