Abstract
An electrochemical nanoflowers manganese oxide (MnO2) catalyst has gained much interest due to its high stability and high specific surface area. However, there are a lack of insightful studies of electrocatalyst performance in nanoflower MnO2. This study assesses the electrocatalytic performances of nanoflower structure MnO2 for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a zinc–air battery as a bifunctional electrocatalyst. The prepared catalyst was characterized in term of morphology, crystallinity, and total surface area. Cyclic voltammetry and linear sweep voltammetry were used to evaluate the electrochemical behaviors of the as-prepared nanoflower-like MnO2. The discharge performance test for zinc–air battery with a MnO2 catalyst was also conducted. The results show that the MnO2 prepared at dwell times of 2, 4 and 6 h were nanoflowers, nanoflower mixed with nanowires, and nanowires with corresponding specific surface areas of 52.4, 34.9 and 32.4 g/cm2, respectively. The nanoflower-like MnO2 catalyst exhibits a better electrocatalytic performance towards both ORR and OER compared to the nanowires. The number of electrons transferred for the MnO2 with nanoflower, nanoflower mixed with nanowires, and nanowire structures is 3.68, 3.31 and 3.00, respectively. The as-prepared MnO2 nanoflower-like structure exhibits the best discharge performance of 31% higher than the nanowires and reaches up to 30% of the theoretical discharge capacity of the zinc–air battery.
Highlights
Renewable energy sources have broadly attracted attention to supply global energy demand due to the excess utilization of petroleum-based fuels [1,2]
The nanoflower structure was produced in a dwell time of 2 h, nanoflower mixed with nanowires was produced in a dwell time of 4 h, and nanowires were produced in a dwell time of 6 h
The nanoflower-like MnO2 catalyst structure was successfully prepared by the hydrothermal method. The formation of such structure was confirmed from the SEM shows image in which the dwell times of 2, 4 and 6 h resulting in nanoflowers, nanoflower mixed with nanowires and nanowires structures, respectively
Summary
Renewable energy sources have broadly attracted attention to supply global energy demand due to the excess utilization of petroleum-based fuels [1,2]. The efficient utilization of renewable energy sources requires safe and cost-effective electricity storage systems. Zinc–air batteries are considered as the most promising alternative energy storage due to several advantages such as high theoretical specific energy density with a flat constant discharge voltage, the low reactivity of zinc, environmental safety and quick refueling with fresh zinc powder and granules. The large overpotential (∆V) between the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) reduces the life cycle and, limiting the performance of the secondary zinc–air batteries [7,8,9,10,11,12]. The development of efficient and stable bifunctional catalysts towards the OER and ORR is critical to support the technology developments
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