Highly porous WO 3 /CNTs-graphite film as a novel and low-cost positive electrode for vanadium redox flow battery
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ORIGINAL PAPER
Highly porous WO3/CNTs-graphite film as a novel and low-cost positive electrode for vanadium redox flow battery Masoud Faraji 1 & Roya Khalilzadeh Soltanahmadi 1 & Soudabeh Seyfi 1 & Borhan Mostafavi Bavani 1 & Hossein Mohammadzadeh Aydisheh 1 Received: 10 December 2019 / Revised: 20 May 2020 / Accepted: 24 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, novel and low-cost tungsten oxide/carbon nanotubes-graphite-polyvinyl chloride (WO3/CNTs-graphitePVC) film with porous 3D network structure and excellent mechanical strength is introduced as an appropriate positive electrode for vanadium redox flow battery (VRFB). The porous WO3/CNTs-graphite-PVC film was easily obtained via uniform adding of Zn nanoparticles (ZnNPs) into bulk structure of CNTs-graphite-PVC composite and then treatment in H2SO4 solution for dissolving of ZnNPs and finally electrodeposition of WO3. Electrochemical investigations revealed an excellent electrocatalytic performance towards the [VO]2+/[VO2]+ redox reaction for the porous WO3/CNTs-graphite-PVC film in contrast to porous CNTs-graphite-PVC, porous WO3/graphite-PVC, and non-porous WO3/CNTs-graphite-PVC films. The excellent electrochemical activity of porous WO3/CNTs-graphitePVC film comes from its high porosity and synergistic effect between CNTs with high electrical conductivity and WO3 with high electrocatalytic nature. Keywords Vanadium redox flow battery . Positive electrode . Porous structure . Graphite
Introduction In recent years, vanadium redox flow battery (VRFB) has taken great attentions as a promising electrochemical storage device for large-scale energy application due to its significant properties such as relatively low maintenance cost, large capacity, long cycle life, and simple monitoring system [1–3]. In a VRFB, the energy is chemically stored in electrolytes, consisting of the positive part corresponding to [VO]2+/[VO2]+ redox reaction and the negative part ascribed to [V]3+/[V]+2 redox reaction (Eqs. 1 and 2) [4–6].
Cathode : VO2 þ H2 O
Charge → ←
VOþ 2 þ 2Hþ þ e
E 0 ¼ 1:00 V
Discharge
ð1Þ Anode : V 3þ þ e
Charge → ←
V 2þ
E0 ¼ −0:26 V
Discharge
ð2Þ
* Masoud Faraji [email protected] 1
Electrochemistry Research Laboratory, Department of Physical Chemistry, Chemistry Faculty, Urmia University, Urmia, Iran
Generally, carbon-based electrodes have been widely used as positive and negative electrodes in the practical application of VRFBs [7, 8]. It has been known that charge transfer kinetic for [VO]2+/[VO2]+ redox reaction in positive electrodes is slower than that of [V]3+/[V]+2 in negative electrodes, leading to decrease power density of VRFB [9, 10]. So, fabrication of positive electrodes with high electrochemical performance has great importance for VRFBs. Among various carbon-based
J Solid State Electrochem
electrodes, graphite has been introduced as a valid positive electrode in VRFBs due to its wide operation potential range, high stability in acidic environment, good conductivity, and
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