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Superior Electrocatalytic Activity of a Robust Carbon‐Felt Electrode with Oxygen‐Rich Phosphate Groups for All‐Vanadium Redox Flow Batteries
Author(s) -
Kim Ki Jae,
Lee Heon Seong,
Kim Jeonghun,
Park MinSik,
Kim Jung Ho,
Kim YoungJun,
SkyllasKazacos Maria
Publication year - 2016
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201600106
Subject(s) - redox , overpotential , inorganic chemistry , chemistry , vanadium , electrochemistry , carbon fibers , oxygen evolution , catalysis , oxygen , electrode , materials science , organic chemistry , composite number , composite material
Abstract 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 (NH 4 PF 6 ), 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 VO 2+ /VO 2 + (in the catholyte) and V 3+ /V 2+ (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 V 3+ /V 2+ 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.