▎ 摘　　要

Monodisperse Cu nanoparticles (NPs) assembled on a pyridinic-N rich graphene (p-NG) support show a Cu NP mass- and size-dependent catalysis for the selective electrochemical reduction of CO2 to ethylene (C2H4). For the 7 nm Cu NPs assembled on the p-NG with the p-NG/Cu mass ratio of 1:1, the C2H4 formation Faradaic efficiency and hydrocarbon selectivity reach 19% and 79% respectively at -0.9 V (vs reversible hydrogen electrode). The p-NG itself can catalyze the CO2 reduction to formate, but in the composite p-NG-Cu structure, the pyridinic-N functions as a CO2 and proton absorber, facilitating hydrogenation and carbon-carbon coupling reactions on Cu for the formation of C2H4. The work demonstrates a new strategy to improve Cu NP catalytic activity and selectivity for the electrochemical reduction of CO2 for sustainable chemistry and energy applications. (C) 2016 Elsevier Ltd. All rights reserved.