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.