Gas Phase Electrolysis of Carbon Dioxide to Carbon Monoxide Using Nickel Nitride as the Carbon Enrichment Catalyst

Nickel nitride was employed as the carbon enrichment electrocatalyst to reduce CO₂ both in the aqueous phase and at the gas–solid interface. In an aqueous electrolyte, the CO Faradaic efficiency reached 85.7% at −0.90 V versus reversible hydrogen electrode with a partial current density of 6.3 mA cm^–2. When gaseous CO₂ was used as a reactant in a flow cell, the CO Faradaic efficiency increased to 92.5% and current density reached 23.3 mA cm^–2. By contrast, metallic Ni and NiO generated predominantly H₂. The increased amount of strong base sites in the Ni₃N catalyst could enrich CO₂ at the catalyst surface, and the utilization of gas phase electrolysis, has cooperatively enhanced reactivity.