Electrochemical Stabilities

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Electrochemical stabilities refer to the ability of a material or system to maintain its chemical and physical properties under electrochemical conditions, particularly during oxidation and reduction reactions. This stability is crucial for the performance and longevity of electrochemical devices, such as batteries and fuel cells, influencing their efficiency and safety.

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Application of carbon materials in redox flow batteries

by Mohd Ali Hashim

2023, Journal of Power Sources

h i g h l i g h t s A comprehensive coverage on carbon materials used in redox flow batteries is given. The influence of nanotechnology and graphene is discussed in detail. The importance of studying RFB degradation mechanisms is... more

Fig. 1. A schematic representation of the most popular RFB system undergoing research to date (all-vanadium). The figure has been adapted from Ref. [9], copyright Elsevier.

Fig. 2. (a) Diagram of a RFB cell with MEA (membrane-electrode assembly) elements and bipolar plates with parallel-channel layout for flow-by distribution;(b) RFB stacks with side fluid feedings—series of about 100 cells with active areas as large as 0.4 x 0.4 m are usual [4] (with permission from Elsevier).

Fig. 3. Cell potential against time during charge/discharge cycles at a current density of 40 mA cm~? for a PSB mono-polar test cell with AC-polyolefin pressed plates as electrode materials | 1,6,66] (with permission from Elsevier). Fig. 3 illustrates the overall cell voltage ofa mono-polar PSB with AC/polyolefin pressed electrodes divided by a Nafion® 115 membrane containing 5 mol dm? NaBr as anolyte and

Fig. 4. Average potential profiles for a packed-bed electrode RFB with a range of separator materials. Taken from Sawyer and co-workers [113], with permission from Springer.

Fig. 5. RFB potential vs. time for a cell with RVC positive and negative electrodes separated by a 4 mm inter-electrode gap in 1.5 mol dm~? Pb(CH3S03), + 0.9 mol dm~? CH3S03H + 1 g dm? Ni(II) + 1 g dm? Na ligninsulfonate [6,126] (with permission from Elsevier). Mean linear flow rate of 10 cm s~! was employed. Due to the large volumetric surface areas, typically 240— 400 cm? cm~? and 5—70 cm? cm~? for the CF [116] and the RVC foam | 117], respectively, three-dimensional carbon-based materials have been employed in various RFB systems [6]. RVC electrodes have also been employed in ZBB [117] and soluble Pb/H2SO,4 RFBs [16]. The porosity of this material is useful in retaining the solid complex of bromide during charging of a ZBB system [118], while the rough surface of the scraped RVC in the soluble Pb/H2SO,4 RFB allows sticky deposits to be formed within the compressed foam structure | 16].

Fig. 6. Potential against time plots for 1-6 and 79-84 charge/discharge cycles at 20 mA cm~? during 15 min charge of the soluble Pb/H2SO, REB. The cell consisted of a Ni foam negative electrode and an RVC positive electrode with 4 mm of inter-electrode gap in 15 mol dm-? Pb(CH3S03)2 + 0.9 mol dm-? CH3SO03H + 1 g dm? Ni(II) + 1 gdm~? Na ligninsulfonate. Mean linear flow rate of electrolyte was 10 cms" 1. Open circuit potential Vo.c, shown in the figure, was 1.86 V [6]. Taken from Hazza et al. [126], copyright Elsevier. Some manufacturers are currently employing polymer-filled expanded graphite board products, however, these materials happen to be very fragile and more expensive than the “conducting plastic” composites [2]. As they tend to be cumbersome to handle in large sizes, some stack developers have preferred to design and manufacture smaller stacks with electrode areas less than 1000 cm? and output power less than 7 kW. Each scalable system integrates energy storage and power management in 175 kW

Fig. 7. Interior view of Innogy’s 12 MW Regenesys™ plant at Little Barford in the UK. Figure was reproduced with kind permission from the Department for Business, Innovation and Skills, Government of U.K. and the ECS [2]. The PSB system was tested with carbon cloth [15] but not in as much detail as for VRBs [13,30,77,81,97,133,134]. Details of cell

Fig. 8. Charging and discharging time against number of cycles for a 2.5 M V-bromide RFB using C material bonded to conductive plastic sheets separated by a Nafion® 112 cationic membrane. The charge/discharge current density was 20 mA cm~? and the cell operated at 20 °C. Obtained from Weber et al. [5] with permission from Springer.

Fig. 9. Charge/discharge performance of carbon plastic electrodes in the VRB at 35 °C {50} (copyright ECS).

Fig. 10. CV obtained at a GC electrode in 1 M VOSO,—2 M H2SO,j solution; scan rates: (1) 100, (2) 200, (3) 300, (4) 400, and (5) 500 mV s~!. Reproduced from Yang et al. [22], copyright ACS as well as from Fang et al. [151], copyright Springer.

Fig. 11. SEM image and charge/discharge curves for CNT grown GFs employed in VRBs. Obtained from Wang et al. [89], with permission from ACS.

CF = carbon felt; GFA = graphite soft felt application (manufactured by SGL); GF = graphite felt; RVC = reticulated vitreous carbon; PVA = polyvinyl acetate; PVDF = polyvinylidene-difluoride; HDPE = high density polyethylene. Carbon electrode materials used for RFB applications are summarised below. NG: not given. Adapted from Leung et al. [6], copyright RSC. Table 1

ko = heterogeneous electrode rate constant; D = diffusion coefficient of electro- active species (in this case vanadium). Standard rate constants (ko) and diffusion constants (D) of V?*/V2+ and VO3 VO**reactions on various electrodes [30] (with permission from ACS).

* [Ru(bpy)3](BF4)2 = tris(2,2’-bipyridine) Ru (II) tetrafluoroborate; Tiron = 4,5-dihydroxy-1,3-benzenedisulfonic acid, disodium salt monohydrate; Ni(bpy)3/Fe(bpy)3 = Ni and Fe tris(2,2’-bipyridine); TEMPO = 2,2,6,€ tetramethyl-1-piperidinyloxy; Ethaline = deep eutectic solvent formed from the hydrogen bond of choline chloride and ethylene glycol.

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Electrochemical synthesis and characterization of conducting copolymers of biphenyl with pyrrole

by Despina Triantou

2022, Journal of Applied Polymer Science

The electrochemical oxidation of anodic metal (zinc or cadmium) in acetonitrile solution of the potentially chelating Schiff base N,N-(dithiodiethylenebis(aminylydenemethylydene)bis(1,2-phenylene)ditosylamide (H 2 L) afforded stable... more

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Growth and Eletrochemical Stability of Compact Tantalum Oxides Obtained in Different Electrolytes for Biomedical Applications

by Ricardo Namur and

2016

Tantalum has been cited to have many biomaterial applications, exhibiting biocompatibility and outstanding corrosion resistance. Tantalum may be covered with tantalum oxide using the electrochemical process of anodic oxidation. The oxide... more

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