Abstract
The constantly growing demand for active, durable, and low-cost electrocatalysts usable in energy storage devices, such as supercapacitors or electrodes in metal-air batteries, has triggered the rapid development of heteroatom-doped carbon materials, which would, among other things, exhibit high catalytic activity in the oxygen reduction reaction (ORR). In this article, a method of synthesizing nitrogen-doped graphene is proposed. Few-layered graphene sheets (FL-graphene) were prepared by electrochemical exfoliation of commercial graphite in a Na2SO4 electrolyte with added calcium carbonate as a separator of newly-exfoliated FL-graphene sheets. Exfoliated FL-graphene was impregnated with a suspension of green algae used as a nitrogen carrier. Impregnated FL-graphene was carbonized at a high temperature under the flow of nitrogen. The N-doped FL-graphene was characterized through instrumental methods: high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical performance was determined using cyclic voltamperometry and linear sweep voltamperometry to check catalytic activity in ORR. The N-doped electroexfoliated FL-graphene obeyed the four-electron transfer pathways, leading us to further test these materials as electrode components in rechargeable zinc-air batteries. The obtained results for Zn-air batteries are very important for future development of industry, because the proposed graphene electrode materials do not contain any heavy and noble metals in their composition.
Highlights
The oxygen reduction reaction (ORR) is important in many energy conversion and storage technologies, including fuel cells, metal-air batteries, and solar-based energy harvesting systems [1,2].Today’s applied energy storage technology is dominated by Li-based batteries, typically exploiting intercalation technology
Graphite particles worked in a way similar to that of the platinum surface, i.e., gas evolved at the graphite, enabling its splitting into less associated graphene structures
Efficiently working electrode materials were developed that could be used in Zn-air batteries with success
Summary
The oxygen reduction reaction (ORR) is important in many energy conversion and storage technologies, including fuel cells, metal-air batteries, and solar-based energy harvesting systems [1,2]. Today’s applied energy storage technology is dominated by Li-based batteries, typically exploiting intercalation technology. Their real energy density is limited to 1000 Wh kg−1.
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