Abstract
In this work, we performed density functional theory (DFT) analysis of nitrogen (N)- and boron (B)-doped graphene, and N,B-co-doped graphene as potential catalysts for rechargeable non-aqueous sodium–air batteries. Four steps of an NaO2 growth and depletion mechanism model were implemented to study the effects of B- and N-doped and co-doped graphene on the reaction pathways, overpotentials, and equilibrium potentials. The DFT results revealed that two-boron- and three-nitrogen (pyridinic)-doped graphene exhibited plausible reaction pathways at the lowest overpotentials, especially during the charging process (approximately 200 mV), thus, significantly improving the oxygen reduction and oxidation reactions of pristine graphene. In addition, pyridinic nitrogen-doped graphene meaningfully increased the equilibrium potential by approximately 0.30 eV compared to the other graphene-based materials considered in this study. This detailed DFT study provides valuable data that can be used for the successful development of low-cost and efficient graphene-based catalysts for sodium–air battery systems operating with non-aqueous electrolyte.
Highlights
In an attempt to make batteries viable for use in future transportation, there has been signi cant research and development of rechargeable metal–air batteries (Li, Na– and Zn–O2/air batteries).[1,2,3,4,5,6,7] A sodium–air battery (Na–O2) consists of sodium metal as the anode and an air/oxygen cathode in which environmental oxygen can be used
When N and B atoms were co-doped and separated by the carbon, more electrons were transferred, indicating that more active sites are created around the doped atoms and more optimal oxygen reduction reaction (ORR) performance can be compared with b-NBG structure (Table 2); see Fig. S2h.† As a result, s-NBG is a better catalyst than single-atom doped structures (NG and boron-doped graphene (BG)) for the ORR process in the presence of protons.[75,76]
It was con rmed that both single- and double-boron-atom-doped graphene exhibited too low dis/charge overpotentials, indicating high catalytic activities towards both the ORR and oxygen evolution reaction (OER) processes compared to other doped graphene samples
Summary
A non-aqueous sodium–air battery system can be constructed by combining a porous carbon material as an air/. N,B-co-doped graphene structures with separated and bonded sites were considered in this study This detailed computational investigation on heteroatom (B and N)-doped and co-doped graphene will increase our understanding of the NaO2 growth and depletion (ORR/ OER) processes in rechargeable non-aqueous Na–O2 batteries and will provide clues regarding the design of novel doped graphene-based catalysts for rechargeable non-aqueous sodium–air batteries
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