Amine-Functionalized Carbon Nanodot Electrocatalysts Converting Carbon Dioxide to Methane.

Yadav, Ram Manohar; Li, Zhengyuan; Zhang, Tianyu; Sahin, Onur; Roy, Soumyabrata; Gao, Guanhui; Guo, Huazhang; Vajtai, Robert et al. · Adv Mater · 2022

basic_science · Level V

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Abstract

The electrochemical conversion of carbon dioxide (CO<sub>2</sub> ) to methane (CH<sub>4</sub> ), 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 CO<sub>2</sub> -to-CH<sub>4</sub> 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 CO<sub>2</sub> -to-CH<sub>4</sub> conversion is presented. Amine functionalized nitrogen-doped GQDs achieve a CH<sub>4</sub> Faradic efficiency (FE) of 63% and 46%, respectively, at CH<sub>4</sub> partial current densities of 170 and 258 mA cm<sup>-2</sup> , approximating to or even outperforming state-of-the-art Cu-based electrocatalysts. These GQDs also convert CO<sub>2</sub> to C<sub>2</sub> products mainly including C<sub>2</sub> H<sub>4</sub> and C<sub>2</sub> H<sub>5</sub> OH with a maximum FE of ≈10%. A systematic analysis reveals that the CH<sub>4</sub> yield varies linearly with amine group content, whereas the C<sub>2</sub> production rate is positively dependent on pyridinic N dopant content. This work provides insight into the rational design of carbon catalysts with CO<sub>2</sub> -to-CH<sub>4</sub> conversion efficiency at the industrially relevant level.