Low Overpotential for Electrochemically Reducing CO₂ to CO on Nitrogen-Doped Graphene Quantum Dots-Wrapped Single-Crystalline Gold Nanoparticles

Electrochemically converting the overemitted CO2 from fossil fuel combustion back into the natural carbon cycle has become a hot spot in recent years. However, surfactants on synthesized nanocatalysts have negative effects on the activity and selectivity. Herein, we transferred the surfactants on single-crystalline gold nanoparticles into N-doped graphene quantum dots (NGQDs) by a hydrothermal method, which not only cleared the Au surfaces but also enhanced the catalytic activity for converting CO2 into CO at ultralow potentials. The highest faradaic efficiency reaches 93% at −0.25 V vs RHE, and CO production starts from as low as −0.15 V, which is much lower than other Au-based nanocatalysts. DFT calculations were applied to investigate the mechanism and indicate that the synergistic effect between gold and NGQDs is a key to increasing activity.