CuO modified ZnO on nitrogen-doped carbon: a durable and efficient electrocatalyst for oxygen reduction reaction

Abstract

The sluggish nature of oxygen reduction reaction (ORR) and the current use of expensive precious metals (platinum [Pt], palladium [Pd], etc.) are barriers to the commercialization and scale-up of fuel cell and metal-air battery technologies. Given this, the development of low-cost non-precious metal-based electrocatalysts with high activity and durability is an area that requires attention. In this study, we report cupric oxide (CuO) modified zinc oxide (ZnO) supported on nitrogen-doped carbon (CuO/ZnO/NC-600) as a desirable electrocatalyst given its activity in alkaline medium, durability, and low cost. The CuO/ZnO/NC-600 catalyst shows excellent ORR activity with an onset potential and half-wave potential (E1/2) of 0.91 V and 0.80 V vs. reversible hydrogen electrode (RHE), respectively, with outstanding limiting current density of 5.34 mA/cm2. The catalyst also displays excellent methanol tolerance, outstanding stability (90 % current retention after 24 h), and durability (only 18 mV half-wave potential shift after 2000 cyclic voltammetry [CV] cycles). The excellent activity and durability of the catalyst are attributed to the synergistic effect of CuO/ZnO and nitrogen-doped carbon. The structure formation of CuO modified ZnO supported on nitrogen doped carbon (CuO/ZnO/NC-600) catalyst provides the advantages associated with excellent conduction of electrons and a large specific surface area (220 m2/g). These, along with the desirable interfacial charge transfer between CuO and ZnO, aid in obtaining the observed ORR activity in CuO/ZnO/NC-600.