Reference Electrodes for Aqueous Solutions

Spitzer, Petra; Wunderli, Samuel; Maksymiuk, Krzysztof; Michalska, Agata; Kisiel, Anna; Galus, Zb́igniew; Tauber, Günter

doi:10.1007/978-3-642-36188-3_5

Cited by 17 publications

(15 citation statements)

References 145 publications

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“…An Ag/AgCl (3 M KCl) electrode (Metrohm A.G.) was used as reference electrode and a Pt-wire electrode as counter-electrode. All the potential values were calculated versus Ag/AgCl, using the reference value + 0.21 V versus SHE at 20 °C [ 56 ].…”

Section: Methodsmentioning

confidence: 99%

Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction

et al. 2021

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The oxygen reduction reaction (ORR) is the rate-limiting reaction in the cathode side of fuel cells. In the quest for alternatives to Pt-electrodes as cathodes in ORR, appropriate transition metal oxide-based electrocatalysts are needed. In the present work, we have synthesized Co3O4 and CoO/Co3O4 nanostructures using flame spray pyrolysis (FSP), as electrocatalysts for ORR in acidic and alkaline media. A detailed study of the effect of (Co-oxide)/Pt ratio on ORR efficiency shows that the present FSP-made Co-oxides are able to perform ORR at very low-Pt loading, 0.4% of total metal content. In acid medium, an electrode with (5.2% Pt + 4.8% Co3O4), achieved the highest ORR performance (Jmax = 8.31 mA/cm2, E1/2 = 0.66 V). In alkaline medium, superior performance and stability have been achieved by an electrode with (0.4%Pt + 9.6% (CoO/Co3O4)) with ORR activity (Jmax = 3.5 mA/cm2, E1/2 = 0.08 V). Using XRD, XPS, Raman and TEM data, we discuss the structural and electronic aspects of the FSP-made Co-oxide catalysts in relation to the ORR performance. Cyclic voltammetry data indicate that the ORR process involves active sites associated with Co3+ cations at the cobalt oxide surface. Technology-wise, the present work demonstrates that the developed FSP-protocols, constitutes a novel scalable process for production of co-oxides appropriate for oxygen reduction reaction electrodes.

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Section: Methodsmentioning

confidence: 99%

Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction

et al. 2021

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“…The most meaningful RE to study ORR with respect to fuel cells is the RHE, which is a hydrogen electrode immersed in the same electrolyte and at 1 bar H 2 partial pressure. 6 Thus, we applied an external RHE and calibrated it separately relative to an internal RHE, as its determination in situ 7,8 is not practical in pressurized cells. Application of the calibrated external RE was tested for studying ORR in conc.…”

Section: 5mentioning

confidence: 99%

Design and Application of External Reference Electrode for Kinetic Studies at Elevated Temperatures and Pressures

Fleige

Wiberg

Arenz

2017

J. Electrochem. Soc.

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We present the design and application of an external reference electrode (RE) system for kinetic studies of the oxygen reduction reaction (ORR), the cathode process in high temperature proton exchange membrane fuel cells (HT-PEMFCs), at elevated temperatures and pressures inside an autoclave. The RE system comprises a solid ion-conducting junction based on Nafion tubing. External RE was a reversible hydrogen electrode (RHE) calibrated reproducibly relative to an internal RHE with an uncertainty <±5 mV over the temperature range of 25-170 • C. Functionality of the RE system was tested by measuring ORR in concentrated H 3 PO 4 relative to a calibrated external RHE. Thus, we are confident that the development is a useful and versatile tool for kinetic studies at elevated temperatures and pressures. Fast and reliable testing of fuel cell catalysts at relevant conditions is of high importance for academia and industry alike. Recently, we introduced an elevated pressure and temperature rotating disk electrode (RDE) system that allows electrocatalytic measurements under well-defined mass transport conditions 1,2 . The setup comprised an internal silver wire RE that enabled a stable determination of the reference potential, but the obtained calibration relative to an internal RHE lacked the required accuracy (< ± 5 mV) for accurate kinetic measurements. We therefore avoided in our previous work the determination of absolute kinetic rates of the ORR at elevated temperature and pressure. An approach to more reliable reference potentials in pressurized cells is to use external RE configurations.3 Recently, external RE systems for fuel cells with solid ion-conducting junctions based on Nafion tubing or the PBI/H 3 PO 4 polymer were published. 4,5Here we present the design and test of an external RE system with solid junction specifically developed for pressurized electrochemical cells. The most meaningful RE to study ORR with respect to fuel cells is the RHE, which is a hydrogen electrode immersed in the same electrolyte and at 1 bar H 2 partial pressure. 6 Thus, we applied an external RHE and calibrated it separately relative to an internal RHE, as its determination in situ 7,8 is not practical in pressurized cells. Application of the calibrated external RE was tested for studying ORR in conc. H 3 PO 4 at elevated temperatures. Such conditions are highly relevant for high temperature proton exchange membrane fuel cells (HT-PEMFC), but usually not accessible to RDE studies due to the low oxygen solubility in the electrolyte. The results demonstrate that our development enables meaningful kinetic studies in pressurized cells and thereby overcomes the significant accuracy issues related to internal REs operated at elevated temperatures. ExperimentalThe electrolyte used in this study was 85 wt% H 3 PO 4 (Suprapur, Merck). The gases used were supplied from gas cylinders (Air Liquide, Denmark) and had a purity of at least 99.995%. The electrochemical cell was placed inside an autoclave as described previously.

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“…The correctness of measurements is determined by the stability of its potential. A classic and most commonly used RE is a silver/silver chloride electrode [24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Encapsulation of Ag/AgCl/Clinto strong hardening polymers such as polyvinyl chloride [51,52] or poly (n-butyl acrylate) [53][54][55] is described in recent studies. SSREs described in [26,[31][32][33]35] keep the potential constant in a solution containing [Fe(CN) 6 ] 3-/4-, but protective polymer layers, in some cases, create a barrier for the penetration of substances generating the analytical signal to the measuring surface. Additionally, the complexity of such electrodes' manufacturing makes their mass use unlikely.…”

Section: Introductionmentioning

confidence: 99%

Silver Chloride/Ferricyanide-Based Quasi-Reference Electrode for Potentiometric Sensing Applications

2020

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Processes’ occurring at the Ag/AgCl/Cl–, ([Fe(CN)6]3–/4–) ions interface study results are presented. Conditions are selected for the mixed salts’ precipitate formation on the silver surface. It has been shown that the potential of a silver screen-printed electrode (AgSPE) coated with a mixed precipitate containing silver chloride/ferricyanide is stable in the presence of [Fe(CN)6]3–/4–. The electrode can serve as a quasi-reference electrode (QRE) in electrochemical measurements in media containing ions [Fe(CN)6]3−/4−. The electrode is formed during polarization of AgSPE (0.325 V vs. Ag/AgCl/KCl, 3.5 M) in a solution containing chloride- and ferri/ferrocyanides ions. The results of the obtained QRE study by potentiometry, scanning electron microscopy and cyclic voltammetry are presented. The proposed QRE was used in a sensor system to evaluate the antioxidant activity (AOA) of solutions by hybrid potentiometric method (HPM). The results of AOA assessment of fruit juices and biofluids obtained using new QRE and commercial Ag/AgCl RE with separated spaces do not differ.

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Reference Electrodes for Aqueous Solutions

Cited by 17 publications

References 145 publications

Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction

Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction

Design and Application of External Reference Electrode for Kinetic Studies at Elevated Temperatures and Pressures

Silver Chloride/Ferricyanide-Based Quasi-Reference Electrode for Potentiometric Sensing Applications

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