Highly-dispersed nickel species on nitrogen-doped porous carbon: Significant local pH-buffering capacity and favorable CO desorption for efficient and robust electro-reduction of CO2

Electrocatalytic reduction of CO2 (CO2RR) to value-added fuels and chemicals can potentially serve as a promising strategy to curb CO2 accumulation and carbon neutral cycle, but is still plagued by sluggish kinetics, poor selectivity and weak durability. Herein, we developed highly-dispersed nickel species on the nitrogen-doped carbon materials (Ni/NC) via the double solvent method (DSM), followed by the pyrolysis. The as-prepared Ni/NC possesses high CO2-to-CO selectivity of 93.2%∼98.6% at broad potential range (0.57 ∼ 0.97 VRHE), decent jCO of 57.9 mAcm−2 at −1.07 VRHE, and significant robustness (retaining 96.3% of the initial faradaic efficiency for CO formation after 50 h electrolysis). As manifested by the rotating ring-disk electrode (RRDE) tests, the DSM-based Ni/NC possesses more significant pH-buffering capacity than Ni nanoparticles, thus promotes the CO2-to-CO. DFT calculations unveil that Ni/NC exhibits relatively lower d-band center, hence resulting in favorable desorption of CO from the catalyst surface that intrinsically boost the CO2-to-CO compared with the nanoparticle catalyst. These results suggest that the DSM-derived Ni/NC catalysts is a promising candidate towards large-scale application of CO2-to-CO.