Superior Electrocatalytic Activity of a Robust Carbon-Felt Electrode with Oxygen-Rich Phosphate Groups for All-Vanadium Redox Flow Batteries

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• 作者：Dr. Ki Jae Kim ; Heon Seong Lee ; Dr. Jeonghun Kim ; Dr. Min-Sik Park ; Prof. Jung Ho Kim ; Dr. Young-Jun Kim and Prof. Maria Skyllas-Kazacos
• 刊名：ChemSusChem
• 出版年：2016
• 出版时间：June 8, 2016
• 年：2016
• 卷：9
• 期：11
• 页码：1329-1338
• 全文大小：2249K
• ISSN：1864-564X

文摘

A newly prepared type of carbon felt with oxygen-rich phosphate groups is proposed as a promising electrode with good stability for all-vanadium redox flow batteries (VRFBs). Through direct surface modification with ammonium hexafluorophosphate (NH₄PF₆), phosphorus can be successfully incorporated onto the surface of the carbon felt by forming phosphate functional groups with −OH chemical moieties that exhibit good hydrophilicity. The electrochemical reactivity of the carbon felt toward the redox reactions of VO²⁺/VO₂⁺ (in the catholyte) and V³⁺/V²⁺ (in the anolyte) can be effectively improved owing to the superior catalytic effects of the oxygen-rich phosphate groups. Furthermore, undesirable hydrogen evolution can be suppressed by minimizing the overpotential for the V³⁺/V²⁺ redox reaction in the anolyte of the VRFB. Cell-cycling tests with the catalyzed electrodes show improved energy efficiencies of 88.2 and 87.2 % in the 1^st and 20^th cycles compared with 83.0 and 81.1 %, respectively, for the pristine electrodes at a constant current density of 32 mA cm⁻². These improvements are mainly attributed to the faster charge transfer allowed by the integration of the oxygen-rich phosphate groups on the carbon-felt electrode.