Title : CuO-ZnO based hybrid system: a durable and efficient electrocatalyst for oxygen reduction reaction
Energy security and environmental pollution are the two most discussed topics in recent times in the research community. Environmental degradation is a significant concern nowadays due to the extensive use of fossil fuels. Also, the depletion of fossil fuels is a matter of concern in energy demand in human society. Given these circumstances, there is an urgent need to develop clean and sustainable energy technology to solve the shortage of fossil fuel-based energy sources and environmental pollution. In this context, among the different energy conversation and storage technology, fuel cell and metal-air batteries have gained enormous interest in recent times. They are known for their high energy density, high efficiency, and clean operation. But the major bottleneck associated with these technologies is oxygen reduction reaction (ORR) which is known for its sluggish nature. The sluggish nature of oxygen reduction reaction and the current use of expensive precious metals (Pt, 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 CuO modified 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. RHE, respectively, with outstanding limiting current density of 5.34 mA cm-2. 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 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 (CuO/ZnO/NC-600) provides the advantages associated with excellent conduction of electrons and a large specific surface area (220 m2 g-1). These, along with the desirable interfacial charge transfer between CuO and ZnO, aids in obtaining the observed ORR activity in CuO/ZnO/NC-600.