Interfacial electron modulation of Cu2O by Co3O4 embedded in hollow carbon cube skeleton for boosting oxygen reduction/revolution reactions

Abstract

Copper (Cu) oxides with various oxidation states are known to be extremely active for oxygen reduction/evolution reactions (ORR/OER). Here, Cu2O-based composites by combining with Co3O4 are designed as non-noble catalysts for ORR/OER by using density-functional-theory (DFT) calculations. Cu-sites in Cu2O-Co3O4 (111) structure are the main active-sites for ORR/OER, which can obtain desirable interfacial charge transfer through favorable energy band arrangements. As inspired by calculation results, Cu2O nanoparticles (20–30 nm) coated on hollow zeolitic imidazolate framework-67 (ZIF-67)-derived nitrogen (N)-doped carbon-cube (HZCNC) with skeleton Co3O4 are prepared as a hollowly-wrapped structure (Cu2O/HZCNC) for boosting ORR/OER, which makes it have the fast electron/mass transfer characteristics. Catalyst marked as Cu2O/HZCNC-0.425 (mass ratio of copper chloride to HZCNC is 0.425) exhibits better ORR activity (E1/2 of 0.90 V) and methanol tolerance than Pt/C, a lower overpotential (350 mV) than RuO2 for OER, and a stable cell voltage gap (0.941 V, average) in a primary zinc-air battery even after 200 h. As indicated by density functional theory results, Cu2O can energetically supply the electrons to the closely-contacted HZCNC (Co3O4) to enhance ORR/OER activities and stabilities. It highlights the excellent functions of Cu-oxides in oxygen electrocatalysis, and provides new insights for development of highly-efficient electrocatalysts with hollow structure.