On the problem of ageing of carbon—air electrodes in alkaline electrolytes

Rolla, A.; Sadkowski, A.; Wild, Joseph; Zoltowski, Piotr

doi:10.1016/0378-7753(80)80106-6

Cited by 23 publications

(26 citation statements)

References 1 publication

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“…Figure 5a shows very positive potentials, it is reasonable to assign its degradation to irreversible oxidation of the active material, which is agreement with other authors [13,31].…”

Section: -Results and Discussionsupporting

confidence: 79%

Section: 2-electrode Preparation and Electrochemical Measurements-supporting

confidence: 78%

“…Additionally, the positive electrode increases very importantly its operating voltage (ΔV), from 0.35 in the first cycle, to 0.5 V after 7,000 cycles, while in the negative electrode this is reduced from 0.22 to only 0.07 V. This indicates that the capacitance of the positive electrode is decreasing with cycling. Considering the shift of this electrode to very positive potentials, it is reasonable to assign its degradation to irreversible oxidation of the active material, which is agreement with other authors [13,31].With the aim of studying the alterations suffered by M-AC upon cycling, the activated carbon was subjected to +0.4V vs. NHE to simulate the processes occurring in the positive electrode in a two-electrode cell after subjected to long-cycling experiments. The oxygen content determined by direct elemental analysis increased drastically, from 3.5 wt.…”

supporting

confidence: 48%

“…carboxy groups) [34], producing carbon corrosion products (CO and CO 2 ) together with oxygen [35,36]. Additionally, the evolution of CO 2 in basic media produces carbonate ions (CO 3 2-) obstructing and retarding the ions mobility in porous materials [31].…”

Section: -Results and Discussionmentioning

confidence: 99%

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Long-term cycling of carbon-based supercapacitors in aqueous media

Ruíz

Santamarı́a

Granda

et al. 2009

Electrochimica Acta

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Abstract.-The behaviour of mesophase-derived electrodes on long-duration cycling conditions was studied in 1M sulfuric acid and 6M potassium hydroxide. Variation in the specific capacitance values with the number of cycles shows a good cycling life performance in acidic media but very poor in an alkaline electrolyte. The total loss of capacitance after 7,000 cycles in acidic media is 8 % at 0.6 V and 16 % at 1 V, whereas in the basic electrolyte the reduction in the capacitance values is 72 %, even at a very small operating voltage (0.6 V). This wide range of applications related to their fast energy delivery (e.g. telecommunications systems, maintenance-free traffic lights, uninterruptible power sources, and hybrid electric vehicles among others) [1]. The storage of energy in electrochemical capacitors can arise from either electrostatic charging or from pseudocapacitative chage-discharge [2]. In the first case, electrolyte ions are accumulated at the electrode/electrolyte interface forming the socalled double layer in a similar way as in conventional capacitors. By utilizing high surface area electrodes the amount of charge stored, and consequently the capacitance of the device, is several orders of magnitude higher than that of conventional electrolytic capacitors. In the second case, pseudocapacitance arises from faradaic processes of electroactive species, such as polymeric materials [3], metal oxides [4,5] and certain functionalities at the surface of carbon materials [6,7,8].It is generally believed that pseudocapacitance in carbon materials is largely based on the redox reactions of surface quinoid functionalities, whose reduction requires protons to proceed [9,10]. Nevertheless, some other oxygenated functional groups might be electrochemically active at the working potentials of the acidic solutions, such as some pyrone groups [11,6]. Therefore, and as may be expected, faradic phenomena have a large dependence on the pH of the solution. In this sense, enormous differences in capacitance values can be found depending on the electrolyte used. For carbon materials in neutral solutions, specific capacitance values between 8-12 μF cm -2 have been reported and between 15-20 μF cm -2 in the case of acidic media [12]. Despite that its study is not so frequent, redox reactions in basic media are also possible [13]. In general terms, the presence of the so-called pseudocapacitance has been related in literature to poor cycle life [19] contrary to what occurs in organic media, where only purely charge separation occurs and good cycling stability is typically reported [20]. Investigations in this field are rarely reported, despite that the cyclability of supercapacitors is a property of mayor importance. The present work investigates the effect of the electrolyte (basic or acidic)in the long-term stability of carbon-based supercapacitors. The electro-oxidation of the activated carbon M-AC was carried out in a conventional three-electrode system. Around 100 mg of material was subjected to +0.4 V vs. NHE in a N 2 bu...

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“…Figure 5a shows very positive potentials, it is reasonable to assign its degradation to irreversible oxidation of the active material, which is agreement with other authors [13,31].…”

Section: -Results and Discussionsupporting

confidence: 79%

Section: 2-electrode Preparation and Electrochemical Measurements-supporting

confidence: 78%

supporting

confidence: 48%

Section: -Results and Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Long-term cycling of carbon-based supercapacitors in aqueous media

Ruíz

Santamarı́a

Granda

et al. 2009

Electrochimica Acta

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“…The increase of C p when increasing the voltage window can be attributed to the creation of functionalities upon cycling. It has been demonstrated by our group, as well as others, that electro-oxidation of electrode materials can occur upon cycling [28][29][30]. The newly introduced functionalities lead to a pseudocapacitance contribution as it has been evidenced in the literature and by some authors.…”

Section: 1-active Materials Characteristics-mentioning

confidence: 56%

Voltage dependence of carbon-based supercapacitors for pseudocapacitance quantification

Ruíz¹,

Roldán²,

Villar³

et al. 2013

Electrochimica Acta

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Abstract.-In order to understand the participation of electrical double layer and pseudocapacitance to the overall behavior of supercapacitors, a new approach to the analysis of the electrochemical data is proposed. Both the variation of the specific capacitance values and the dependence of these values with the operating voltage window (varying from 0-0.2 V to 0-1 V) were evaluated and used to quantify the contribution arising from each mechanism of energy storage to the total capacitance of the system. The suitability of the methodology here proposed was tested in various carbon materials (multiwalled carbon nanotubes, a carbon aerogel and two activated carbons), different both in nature and physicochemical characteristics. For all of the carbons studied, the capacitance with an exclusive faradic and non -faradic origin was quantified. Whereas some of the carbons studied showed a behavior close to an ideal Electrical Double Layer Capacitor (EDLC) with virtually no pseudocapacitance contribution (case of the carbon nanotubes), others presented up to a 40 % of pseudocapacitance contribution (case of KOH -activated carbon).

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Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

et al. 2019

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Managing the gas–liquid interface within gas‐diffusion electrodes (GDEs) is key to maintaining high product selectivities in carbon dioxide electroreduction. By screening silver‐catalyzed GDEs over a range of applied current densities, an inverse correlation was observed between carbon monoxide selectivity and the electrochemical double‐layer capacitance, a proxy for wetted electrode area. Plotting current‐dependent performance as a function of cumulative charge led to data collapse onto a single sigmoidal curve indicating that the passage of faradaic current accelerates flooding. It was hypothesized that high cathode alkalinity, driven by both initial electrolyte conditions and cathode half‐reactions, promotes carbonate formation and precipitation which, in turn, facilitates electrolyte permeation. This mechanism was reinforced by the observations that post‐test GDEs retain less hydrophobicity than pristine materials and that water‐rinsing and drying electrodes temporarily recovers peak selectivity. This knowledge offers an opportunity to design electrodes with greater carbonation tolerance to improve device longevity.

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On the problem of ageing of carbon—air electrodes in alkaline electrolytes

Cited by 23 publications

References 1 publication

Long-term cycling of carbon-based supercapacitors in aqueous media

Long-term cycling of carbon-based supercapacitors in aqueous media

Voltage dependence of carbon-based supercapacitors for pseudocapacitance quantification

Investigating Electrode Flooding in a Flowing Electrolyte, Gas‐Fed Carbon Dioxide Electrolyzer

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