Nitrogen-Rich Carbon Nanomaterials Embedded with Ni Nanoparticles for Electrochemical Carbon Dioxide Reduction

Porphyrins with earth-abundant transition metals are appealing catalysts for the CO2 electrochemical reduction reaction (CO2ERR). However, their wider applications are often limited by aggregation and instability. Herein, a facile thermal treatment was employed to convert metal porphyrins into metal nanoparticles embedded in nitrogen-rich carbon nanomaterials. It was found that Ni nanoparticles derived from Ni porphyrins show a high selectivity of 93% toward CO with an exceptional onset overpotential of 320 mV, while Co nanoparticles derived from Co porphyrins exhibit a selectivity of 16% only as well as a high overpotential of 730 mV. The above contrast indicates that the derived metal nanoparticles exert huge effects on the selectivity and activity. Density functional theory (DFT) calculations reveal that metal nanoparticles would alter the energy barriers of the CO2ERR and the competitive hydrogen evolution reaction (HER), both of which jointly affect the catalytic selectivity. The findings here provide not only a better understanding of the relationship between catalytic metal sites and selectivity but also deeper insights into the design of advanced catalysts for CO2ERR.