Roles of Oxygen Functional Groups in Carbon Nanotubes-Supported Ag Catalysts for Electrochemical Conversion of CO2 to CO

Graphical Multiple roles : Three carbon nanotubes (CNTs)-supported Ag catalysts with precise tuning oxygen functional groups were reasonably designed/synthesized and applied into efficient electrochemical conversion of CO 2 to CO. The surface carboxyl groups on the CNTs play essential roles in loading Ag nanoparticles and tuning surface acidic environment of catalysts, and the rich surface protons are proved to be important for promoting the formation of intermediate, which could effectively improve the CO production. Carbon nanotubes (CNTs)-supported metal-based catalysts applied in the electrochemical reduction of CO 2 (CO 2 ER) have attracted extensive research recently. Nevertheless, insight into the roles of surface oxygen functional groups in these catalysts on CO 2 ER is still deficient. Herein, three catalysts were reasonably fabricated by chemically loading Ag nanoparticles (NPs) on the oxygenic CNTs (CNT−COOH, CNT−OH and CNT−CO) with precise tuning oxygen functional groups, and then used to explore the effect of oxygen functional groups on the electrocatalytic performance of Ag NPs for CO 2 ER. Compared with the other two counterparts, Ag/CNT−COOH with the highest content of carboxyl groups possesses the most uniform size and dispersion of Ag NPs and the strongest surface acidic environment, which enable it to exhibit the highest current density and Faradaic efficiency for CO production at high overpotential region ( E ≤−1.0 V vs. RHE). This work broadens the understanding of surface oxygen functional groups of catalysts in enhancing CO 2 ER performance, and provides guidance for the design and synthesis of high-performance catalysts.