The Role of Oxygenic Groups and sp 3 Carbon Hybridization in Activated Graphite Electrodes for Vanadium Redox Flow Batteries
Ali Hassana b c d e, Asnake Sahele Hailef g, Théodore Tzedakisc, Heine Anton Hansenb e, Piotr de Silvab e✉
- aChemical Engineering Department MNS University of Engineering and Technology QasimPur Colony, BCG Chowk Multan Punjab Pakistan
- bDepartment of Energy Conversion and Storage Technical University of Denmark 2800 Kgs. Lyngby Denmark
- cLaboratoire de Génie Chimique UMR CNRS 5503 Université de Toulouse UT-III-Paul Sabatier 118 Route de Narbonne 31062 Toulouse France
- dChemical Engineering Department, MNS University of Engineering and Technology, QasimPur Colony, BCG Chowk, Multan, Punjab, Pakistan
- eDepartment of Energy Conversion and Storage, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- fCenter for Environmental Science College of Natural and Computational Sciences Addis Ababa University P.O. Box 1176 Addis Ababa Ethiopia
- gCenter for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University, P.O. Box, 1176 Addis Ababa, Ethiopia
- ✉Corresponding author
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Abstract
Abstract Graphite felt is a widely used electrode material for vanadium redox flow batteries. Electrode activation leads to the functionalization of the graphite surface with epoxy, OH, C=O, and COOH oxygenic groups and changes the carbon surface morphology and electronic structure, thereby improving the electrode's electroactivity relative to the untreated graphite. In this study, density functional theory (DFT) calculations are conducted to evaluate functionalization's contribution towards the positive half‐cell reaction of the vanadium redox flow battery. The DFT calculations show that oxygenic groups improve the graphite felt's affinity towards the VO 2+ /VO 2 + redox couple in the following order: C=O>COOH>OH> basal plane. Projected density‐of‐states (PDOS) calculations show that these groups increase the electrode's sp 3 hybridization in the same order, indicating that the increase in sp 3 hybridization is responsible for the improved electroactivity, whereas the oxygenic groups’ presence is responsible for this sp 3 increment. These insights can aid the selection of activation processes and optimization of their parameters.
TL;DRIt is concluded that the increase in the sp3 hybridization is responsible for the improved electroactivity, while the oxygenic groups' presence is responsibleFor the better selection of activation processes and optimization of their parameters. (Semantic Scholar)