Understanding efficient phosphorus-functionalization of graphite for vanadium flow batteries. (20th March 2022)

• Record Type: Journal Article
• Authors: Radinger, Hannes; Hartmann, Mark; Ast, Marius; Pfisterer, Jessica; Bron, Michael; Ehrenberg, Helmut; Scheiba, Frieder
• Is Part Of: Electrochimica acta. Volume 409(2022)
• Publication Date: 2022-03-20
• Subjects: Vanadium redox flow battery -- Electrocatalytic activity -- Graphite electrode -- Phosphorus doping -- Surface functionalization; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2022.139971
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: Numerous surface treatment methods are known to enhance the electrochemical activity of graphite felt (GF), such as thermal activation or attachment of nanoparticulate catalysts. The integration of heteroatoms into the graphite lattice at the surface could be a promising technique for reliable and efficient electrode activation. However, these functionalization techniques are based on thermochemical activation, which makes it difficult to distinguish between activity effects other than foreign atom integration, such as defects and other surface groups that must be considered. In this work, we analyzed commercial and synthetic phosphorus-doped graphene and GF using different electrochemical and physicochemical techniques. Despite a high doping concentration, the activity of the commercial powder bonded to GF and coated on glassy carbon remained limited due to the low degree of graphitization and high oxygen content. Instead, a low phosphorus concentration of <1 at% combined with a high degree of graphitization increased the catalytic activity. Building on these findings, GF was rationally modified, resulting in twice the power density compared to the original material in full cell tests.