(265c) Developing Carbon Nanomaterials Electrocatalysts for Active and Selective Carbon Dioxide to Target Products Conversion

Electrocatalytic reduction of CO₂ into value-added chemicals or fuels is a promising technique for a carbon-neutral chemical process. The electrochemical reduction of CO₂ is a complicated process involving multiple protons coupled electron transfer, theoretically resulting in various products. Therefore, the major challenge in CO₂ reduction lies in manipulating the selectivity toward a specific product. 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 multi-electron transfer processes. Researchers have screened a wide range of metal materials for electrochemical CO₂ reduction and found only copper metals exhibit selectivity towards hydrocarbons and oxygenates with decent efficiencies, while most others favor the production of CO or HCOO^-. Here we present the development of carbon nanomaterials as an alternative to Cu for selective and high-rate electro-reduction of CO₂ into hydrocarbons and oxygenates. We will discuss the critical structural and electronic factors that govern the selectivity of carbon catalysts for the production of CO, CH_4, and C₂ products (e.g. C₂H₄ and C₂H₅OH). Three categories of carbon catalysts were developed based on the primary products of CO, CH_4, 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 graphene quantum dots (GQDs), can selectively reduce CO₂ into CH₄ with Faradaic efficiency (FE) of up to 70%. The third one, doped and H-passivated GQDs, yield C_≥2 products with FE of 70%. All catalysts show an industrial relevance current density of > 200 mA cm^-2. This study provides in-depth insights into developing high-performance carbon-based catalysts for electrochemical CO₂ reduction.