Cobalt Nanoparticles Dispersed Nitrogen-Doped Graphitic Nanospheres-Based Rechargeable High Performance Zinc−Air Batteries

Abstract

The zinc−air battery (ZAB) is an emerging rechargeable energy storage system having high energy density (1084 Wh/kg) with safe operation and low operation cost (∼$10 kW/h). Development of a durable and efficient bifunctional catalyst is the bottleneck of rechargeable ZAB technology, and here we demonstrate a hybrid catalyst system having cobalt (Co) nanoparticles dispersed graphitic spheres as an efficient catalyst at the air electrode—performing better than the benchmarked ones while constructing the ZAB cells. Co nanoparticles dispersed nitrogen-doped graphitic nanospheres (Co@NGC-NSs) were developed using a unique synthesis strategy, and it showed excellent bifunctional catalytic activity toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. The potential difference calculated with Co@NGC-NSs, considering the potential for the current density of 10 mAcm−2 for OER and current density corresponding to the half wave potential for ORR, is found to be (0.78 V) lower than that of Pt/C and IrO2 (0.87 V) system. The zinc−air cell constructed using Co@NGC-NSs shows an open circuit voltage of 1.36 V having a maximum power density of ∼52 mW cm−2 and an energy density of 876 Wh/kg, and these values are on par with the Pt/C system while much better in terms of long-term stable performance where Pt/C is found to be failing. A detailed comparison with the reported performance of other catalyst-based ZABs indicates that the Co@NGC-NSs-based ZABs has high potential as a practically viable system, where the catalyst development is also found to be simple and nonexpensive in nature.