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

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Summary

Introduction

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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