ZIF-derived bifunctional Cu@Cu–N–C composite electrocatalysts towards efficient electroreduction of oxygen and carbon dioxide

A [email protected]–N–C composite electrocatalyst with metallic Cu NPs and Cu(II)-Nx species embedded into the carbon matrix was pyrolyzed from ZIF-8 precursor through the formation of Cu(OH)2@ZIF-8. The optimal [email protected]–N–C catalyst obtained at 1000 °C features a hollow polyhedral morphology, which is resulted from the carbothermal reaction of in-situ generated Cu2O and ZnO with carbon beyond 800 °C. The best-performance [email protected]–N–C exhibits an impressive catalytic bifunction towards oxygen reduction reaction (ORR) and carbon dioxide reduction (CO2RR) which is assumed to be imparted by the unique Cu(0)-Cu(II)-Nx active sites. In alkaline electrolyte, it shows the ORR performance (E1/2 = 0.83 V vs RHE) comparable to Pt/C (E1/2 = 0.85 V vs RHE), and the assembled zinc-air (Zn-air) battery displays an excellent durability with the open circuit voltage (1.23 V) decaying only by ca. 4.2% in 80 h at 20 mA cm−2. For CO2RR, it also delivers an outstanding catalytic performance converting CO2 into CO with a high Faradaic efficiency (90% at −0.5 V vs RHE). Control experiments have indicated that the potential synergistic interactions between Cu (0) (from Cu NPs) and Cu-Nx sites have promoting effects on both ORR and CO2RR.