Amine-Functionalized Carbon Nanodot Electrocatalysts Converting Carbon Dioxide to Methane

The electrochemical conversion of carbon dioxide (CO₂ ) to methane (CH₄ ), which can be used not only as fuel but also as a hydrogen carrier, has drawn great attention for use in supporting carbon capture and utilization. The design of active and selective electrocatalysts with exceptional CO₂ -to-CH₄ conversion efficiency is highly desirable; however, it remains a challenge. Here a molecular tuning strategy-in situ amine functionalization of nitrogen-doped graphene quantum dots (GQDs) for highly efficient CO₂ -to-CH₄ conversion is presented. Amine functionalized nitrogen-doped GQDs achieve a CH₄ Faradic efficiency (FE) of 63% and 46%, respectively, at CH₄ partial current densities of 170 and 258 mA cm^-2 , approximating to or even outperforming state-of-the-art Cu-based electrocatalysts. These GQDs also convert CO₂ to C₂ products mainly including C₂ H₄ and C₂ H₅ OH with a maximum FE of ≈10%. A systematic analysis reveals that the CH₄ yield varies linearly with amine group content, whereas the C₂ production rate is positively dependent on pyridinic N dopant content. This work provides insight into the rational design of carbon catalysts with CO₂ -to-CH₄ conversion efficiency at the industrially relevant level.