Decisive Intermediates Responsible for the Carbonaceous Products of CO₂ Electro‐reduction on Nitrogen‐Doped sp² Nanocarbon Catalysts in NaHCO₃ Aqueous Electrolyte

Nitrogen‐doped sp 2 nanocarbon materials have been considered promising catalysts for CO 2 electro‐reduction. However, a fundamental understanding about product selectivity and the reaction routes is still lacking. In this report, the reaction mechanism on nitrogen‐doped sp 2 nanocarbon materials is resolved by clarifying the authentic origin of the carbonaceous products: CO and HCO 2 − . Two carbon‐reduction pathways are identified based on a series of comparative studies by using differential electrochemical mass spectrometry and in situ CO adsorption experiments: a dominant pathway leading to CO from CO 2 and a secondary pathway leading to HCO 2 − from HCO 3 − . Neither hydrocarbon (C x H y ) nor alcohol or aldehyde (C x H y O z ) were detected in the reduction of CO 2 . However, CO, which is generally regarded as an intermediate to be transformed into these products on metal catalysts, can undoubtedly be produced and adsorbed on nitrogen‐doped sp 2 nanocarbon catalysts during the reaction.