Starbon with Zn-N and Zn-O active sites: An efficient electrocatalyst for oxygen reduction reaction in energy conversion devices

The design of efficient and cost effective catalysts for the energy conversion and storage devices is a crucial step towards their economic commercialization. Here we report synthesis of nitrogen doped starbon/zinc oxide composite (NS/ZnO), which shows enhanced electrocatalytic activity towards oxygen reduction reaction (ORR). NS/ZnO was synthesized by high temperature annealing of a mixture of alginic acid, zinc chloride and urea, where nitrogen doping in starbon and the formation of Zn-Nx functionalities play an important role in the electrochemical property studies. Remarkably, NS/ZnO composite exhibited onset potential (Eonset) around 1.11 V with substantial half wave potential (E1/2) of 1.02 V vs RHE for ORR. Thus, it showed a high shift to positive voltage compared to commercial Pt/C by 140 mV vs RHE with durability up to 15,000 potential cycles. NS/ZnO composite was also tested for methanol tolerance and was found to be highly selective towards ORR over methanol oxidation reaction (MOR) unlike the commercial Pt/C catalyst. Detailed structural analysis of the composite revealed that ZnO nanostructures and Zn-Nx sites at the interface formed due to interaction of ZnO with N-doped starbon are the key factors responsible for its catalytic performance towards ORR and the stability. Thus, NS/ZnO composite could find potential applications in energy conversion and storage devices.