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

Abstract

As the size of atomic nickel increased to nanoscale particles, the electrocatalytic CO2 reduction reaction (CO2RR) was subjected to intense hydrogen evolution side reactions and significant *CO adsorption, which markedly influenced the activity and selectivity of CO2RR. This study introduces highly graphitized nitrogen-doped ordered mesoporous carbon as a support for dispersing Ni nanocrystals. This support provides effective mass transfer pathways and exposes a substantial number of catalytic Ni sites. The obtained catalyst achieved a peak CO Faradaic efficiency (FECO) of ~100% at −0.8 V vs. RHE, with FECO consistently exceeding 90% across a wide potential window from −0.7 to −1.0 V vs. RHE. Besides, it also exhibits hydrazine oxidation (HzOR) activity with a current density of 10 mA cm−2 at a potential of 1.1 V lower than that for water oxidation. Impressively, when coupling the thermodynamically favorable HzOR with CO2RR in a two-electrode electrolyzer, achieving a theoretical energy saving of 33%. Furthermore, during the stable operation of this electrolyzer for 60 hours, its FECO remained consistently above 90%. This work provides valuable insights into the rational design of advanced Ni-based materials for CO2RR and develops a more cost-effective CO2 splitting system.