CuO-ZnO Based Heterostructure Supported on Nitrogen-Doped Carbon for Oxygen Reduction Catalysis

Abstract

Innovation in energy conversion technologies is urgently needed to ensure a secure and sustainable future. Environmental pollution is a major concern due to the extensive use of fossil fuels to meet the current energy requirements. Also, with the imminent shortage of fossil fuels, rising population, and increasing energy demand, the need for clean, low-cost, sustainable energy technologies is on the rise. Among the various energy storage and conversion technologies, metal-air batteries and fuel cells offer a combination of cost-effectiveness, clean operation, and high energy density. However, the kinetically sluggish oxygen reduction reaction (ORR) makes these energy storage and conversion systems expensive as sluggishness is compensated with high platinum loading. Developing cost-effective electrocatalysts that can speed up ORR is vital to developing next-generation electrochemical energy devices. In this work, we have transformed ORR inactive ZnO into highly active electrocatalyst via heterostructure formation with CuO oxide. We report a CuO-ZnO-based heterostructure supported on nitrogen-doped carbon (CuO/ZnO/NC-600) for ORR in an alkaline medium. The onset and halfwave potential of CuO/ZnO/NC-600 catalyst are 0.905 V and 0.795 V vs. RHE, respectively. CuO/ZnO/NC-600 shows a nearly four-electron transfer per O2 with significantly less H2O2(5%) production and excellent kinetics (Tafel slop is 68 mV dec-1). The catalyst shows excellent stability (90 % current retention after 24 h) when tested by chronoamperometry and exhibits methanol tolerance qualifying itself for direct methanol fuel cell applications. Figure 1