Electrocatalytic reduction of CO₂ into value added chemicals or fuels is a promising technique towards a carbon-neutral chemical process. The electrochemical reduction of CO₂ is a complicated process involving multiple protons coupled electron transfer, theoretically resulting in a variety of products (e.g. CO, HCOOH, CH₄, C₂H₄ and C₂H₅OH). Therefore, the major challenge in CO₂ reduction lies in the manipulation of the selectivity towards a specific product as demanded. However, the study on CO₂ reduction has not substantially advanced primarily because of the lack of fundamental understanding of the reaction mechanism and the challenge of discovering efficient and robust catalysts for the various multi-electron transfer processes. Researchers have screened a wide range of metal-based materials for electrochemical reduction of CO₂, and found only copper-based metals exhibit selectivity towards formation of hydrocarbons and oxygenates at fairly high efficiencies while most others favor production of carbon monoxide or formate.

Here we present the development of carbon materials as an alternative to Cu for efficient and high-rate electro-reduction of CO₂ into hydrocarbons and oxygenates. We will discuss the key structural and electronic factors that govern the selectivity of carbon catalysts towards production of CO, CH₄ and C₂ products (e.g. C₂H₄ and C₂H₅OH). Three categories of carbon catalysts were developed based on the primary products of CO, CH₄ and C₂H₄ in our group. The first carbon catalyst featuring the metal-nitrogen-carbon structure exclusively catalyzes CO₂ electro-reduction into CO. The second catalyst called functionalized carbon nanostructure can selectively reduce CO₂ into CH₄ with Faradaic efficiency up to 90% while the third one namely doped carbon nanostructure (e.g. N-doped graphene quantum dots) can yield C_≥2 products with a Faradaic efficiency up to 70%. Both carbon nanostructure can achieve partial current density at the scale of 100 mA cm^-2 for target product at fairly low overpotentials. This study provides in-depth insights into developing high-performance carbon-based catalysts for electrochemical reduction of CO₂.