Highly graphitized nitrogen-doped ordered mesoporous carbon supported Ni nanocrystals for efficient hydrazine-assisted CO2 splitting

Abstract

The reaction activity and product selectivity of the CO₂ electroreduction process are hindered by intense hydrogen evolution and substantial *CO adsorption when nickel particle size is increased to the nanoscale dimension. This study introduces a highly graphitized nitrogen-doped ordered mesoporous carbon (Ni-NC) as a support for dispersing Ni nanocrystals, which not only enhances mass transfer but also exposes abundant catalytic Ni sites. In situ electrochemical measurements, characterization, and density functional theory calculations revealed that the synergistic interaction between nickel nanocrystals and the nitrogen-doped carbon matrix promoted CO₂ adsorption and the formation of the *COOH intermediate. Ni-NC achieved a peak CO faradaic efficiency (FE_CO) of ∼100% at −0.8 V vs. RHE, maintaining FE_CO above 90% across a wide potential window from −0.7 to −1.0 V vs. RHE. Additionally, Ni-NC efficiently catalyzed hydrazine-assisted CO₂ decomposition, offering up to 69% theoretical energy savings compared to traditional water oxidation-coupled systems in MEA while consistently maintaining a cathodic FE_CO above 90% across a broad cell voltage range, offering valuable insights for the development of more cost-effective CO₂ splitting systems.