Modulable Cu(0)/Cu(I)/Cu(II) sites of Cu/ C catalysts derived from MOF for highly selective CO2 electroreduction to hydrocarbons

Abstract

Electrocatalytic CO2 reduction has been perceived as sustainable to realize the closed-loop carbon cycle and obtain high-energy-dense fuels and chemicals. Nevertheless, the efficient CO2 reduction into specific hydrocarbons is still highly challenging. In particular, the effects of Cu(0)/Cu(I)/Cu(II) active sites in copper-based catalysts remain elusive. Hence, this work investigated the modulable valence states of Cu(0)/Cu(I)/Cu(II) active sites derived from MOF Cu(btc) under different calcination conditions to enhance CO2RR performance. As evidenced by characterizations, the Cu/C-T-air was more inclined to produce C2H4, which may be associated with Cu(I)/Cu(II) coexistence and abundant oxygen vacancy. Cu/C-450-air showed excellent CO2RR properties with 34.8% Faradaic efficiency of C2H4 at 1.1 V vs. RHE after a continuous measurement of 12 h. Meanwhile, the Cu/C-T-H2 was inclined to produce C2H4, while Cu/C-T-N2 tended to produce CH4, which may be associated with smaller grain size and thinner carbon layer than the latter to exposure to more active sites and rapid electron transport. Moreover, the mechanism of electrocatalytic CO2 reduction of Cu/C-T-gas was conjectured. We furnished rational thinking to design Cu/C catalysts with tunable active sites to bolster CO2RR.