Carbon quantum dot-covered porous Ag with enhanced activity for selective electroreduction of CO2 to CO

Abstract

Ag is a promising efficient catalyst for selective electroreduction of CO₂ to CO. However, challenges such as high overpotential and poor stability for Ag in CO₂ electroreduction still remain unsolved. In this work, we demonstrate that a carbon quantum dot (CQD)-covered porous Ag (p-Ag/CQD) composite can efficiently reduce CO₂ to CO with a maximum CO faradaic efficiency of 83.2% at the potential of −0.8 V (vs. RHE). The p-Ag/CQD composite exhibits a 6.3-fold and 20.8-fold enhancement of CO current density relative to porous Ag and Ag foil, respectively, and shows a more stable current density during the 4 h electrolysis. The dramatically enhanced catalytic activity of the p-Ag/CQD composite should be ascribed to its porous structure and the existence of CQDs on its surface. The existing CQDs can improve the abilities of CO₂ adsorption/CO desorption and stabilize the CO₂⁻ intermediate to achieve a lower overpotential compared with porous Ag and Ag foil. More importantly, the synergistic effect of porous Ag and CQDs has a significant catalytic effect on the CO₂ reduction reaction.