How Nitrogen-Doped Graphene Quantum Dots Catalyze Electroreduction of CO2 to Hydrocarbons and Oxygenates

5 years ago

How Nitrogen-Doped Graphene Quantum Dots Catalyze Electroreduction of CO2 to Hydrocarbons and Oxygenates

Jingjie Wu, Pulickel M. Ajayan, Boris I. Yakobson, Bilu Liu, Jia Li, Mingjie Liu, Xiaolong Zou

Recently, metal-free nitrogen-doped graphene quantum dots (NGQDs) have been experimentally demonstrated to electrochemically convert CO₂ into high-order hydrocarbons and oxygenates, after more than 30 years since the identification of copper as an active metal catalyst for such conversions. However, the physicochemical principle of such catalytic activity for NGQDs has remained unclear. Here, by performing first-principles simulations, we have systematically investigated the underlying mechanisms governing the whole process. The introduction of N atoms into edges of graphene quantum dots enhances their bonding with *COOH, effectively promoting the reduction of CO₂ to CO. By including the influences of water, we reveal that the selective production of CH₄ over CH₃OH is attributed to a much lower kinetic barrier for the conversion of adsorbed *CH₂OH to *CH₂ via water molecule mediated proton shuttling. Further, adsorbed *CH₂ provides active sites for the coupling with CO to generate C₂ products, including both C₂H₄ and C₂H₅OH. These results offer theoretical insights into the reduction pathways of CO₂ on NGQDs, which may facilitate the design of metal-free carbon-based catalysts for efficient CO₂ reduction.

Publisher URL: http://dx.doi.org/10.1021/acscatal.7b01839

DOI: 10.1021/acscatal.7b01839