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Reference electrode

About: Reference electrode is a research topic. Over the lifetime, 16901 publications have been published within this topic receiving 259568 citations.


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TL;DR: The results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.
Abstract: Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 micro M), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 micro mol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E(o)' =+0.37 V). The production of current in microbial fuel cell (65 mA/m(2) of electrode surface) or poised-potential (163 to 1,143 mA/m(2)) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.

2,133 citations

Book
01 Jan 2008
TL;DR: In this paper, the authors provide guidelines for experimental design, discuss the relevance of accuracy contour plots to wiring and instrumentation selection, and emphasize the importance of the Kramers-Kronig relations to data validation and analysis.
Abstract: Electrochemical impedance spectroscopy (EIS) is a powerful tool to investigate properties of materials and electrode reactions. This Primer provides a guide to the use of EIS with a comparison to other electrochemical techniques. The analysis of impedance data for reduction of ferricyanide in a KCl supporting electrolyte is used to demonstrate the error structure for impedance measurements, the use of measurement and process models, as well as the sensitivity of impedance to the evolution of electrode properties. This Primer provides guidelines for experimental design, discusses the relevance of accuracy contour plots to wiring and instrumentation selection, and emphasizes the importance of the Kramers-Kronig relations to data validation and analysis. Applications of EIS to battery performance, metal and alloy corrosion, and electrochemical biosensors are highlighted. Electrochemical impedance measurements depend on both the mechanism under investigation and extrinsic parameters, such as the electrode geometry. Experimental complications are discussed, including the influence of nonstationary behaviour at low frequencies and the need for reference electrodes. Finally, emerging trends in experimental and interpretation approaches are also described.

1,497 citations

Journal ArticleDOI
TL;DR: The iodide/triiodide redox couple has good solubility, does not absorb too much light, has a suitable redox potential, and provides rapid dye regeneration, and it is expected that overall efficiencies above 15% might be achieved if half of this internal potential loss could be gained.
Abstract: Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions. The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO2 electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes. The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO2 electrode through the recombin...

1,296 citations

Journal ArticleDOI
TL;DR: In this paper, a critical review of conversion constants amongst various reference electrodes reported in the literature reveals that in most cases the comparisons of redox potential values are far from accurate, and therefore, caution should be exercised when one is comparing the redox properties of complexes measured in CH 3 CN solutions versus different reference electrodes.

1,212 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that in principle three reference levels can be chosen to measure an absolute value of the electrode potential, and a thermodynamic analysis of the components of the emf of an elec- trochemical cell is shown.
Abstract: The document begins with the illustration of the most widespread misunderstandings in the literature about the physical meaning of absolute electrode potential. The correct expression for this quantity is then de— rived by a thermodynamic analysis of the components of the emf of an elec— trochemical cell. It is shown that in principle three reference levels can be chosen to measure an absolute value of the electrode potential. Only one of these possesses all the requisites for a meaningful comparison on a con— mon energy scale between electrochemical and physical parameters. Such a comparison is the main problem for which the adoption of a correct scale for absolute electrode potentials is a prerequisites. The document ends with the recommendation of a critically evaluated value for the absolute potential of the standard hydrogen electrode in water and in a few other protic solvents. The \"electrode potential\" is often misinterpreted as the electric potential difference between a point in the bulk of the solid conductor and a point in the bulk of the electrolyte solution (L4) (Note a). In reality, the transfer of charged particles across the electrode/electrolyte solution interface is controlled by the difference in the energy levels of the species in the two phases (at constant T and p), which includes not only electrical (electric potential difference) but also chemical (Gibbs energy difference) contributions since the two phases are compositionally dissimilar (refs. 1,2). The value of the tjq of a \"single\" electrode, e.g. one consisting of an electronic conductor in contact with an ionic conductor, is not amenable of direct experimental determination. This is because the two metallic probes from the measuring instruments, both made of the same material, e.g. a metal M1, have to be put in contact with the bulk of these two phases to pick up the signal there. This creates two additional interfaces: a M1/solution interface, and a M1/electrode metal interface. The experimental set-up can be sketched as follows: M1 SIMIMI (1) where M is the metal of the electrode under measure, S is the electrolyte solution, M1 is the metal of the \"connections\" to the measuring instrument and the prime on M indicates that this terminal differs from the other one (M1) by the electrical state only. It is expedient to replace the M1/S interface with a more specific, reproducible and stable system known as the reference electrode. It ensues that an electrode potential can only be measured against a reference system. The measured quantity is thus a relative electrode potential. For the specific example of cell (1), the measured quantity E, the electrode potential of M relative to M1 (Note b), is conventionally split into two contributions, each pertaining to one of the electrodes: EEM_EM1 (2) EM and EM1 can be expressed in their own on a potential scale referred to another reference electrode. In this respect, the hydrogen electrode is conventionally taken as the universal Note a: This quantity, known as the Galvani potential difference between M and 5, has been defined in ref. 3. Note b: In accord with the IUPAC convention on the sign of electrode potentials, all electrode potentials in this document are to be intended as \"reduction potentials\", i.e. the electrode reaction is written in the direction of the reduction (refs. 3,4). 956 Absolute electrode potential (Recommendations 1986) 957 (for solutions in protic solvents) reference electrode for which, under standard conditions, E°(H/H2) = 0 at every temperature (Note c). Since EM as measured is a relative value, it appeals to many to know what the absolute value may be: viz. , the value of EM measured with respect to a universal reference system not including any additional metal/solution interface. Actually, for the vast majority of practical electrochenilcal problems, there is no need to bring in absolute potentials . The one outstanding example where this concept is useful is the matching of semiconductor energy levels and solution energy levels . However, from a fundamental point of view, this problem comes necessarily about in every case one wants to connect the \"relative\" electrode potential to the \"absolute\" physical quantities of the given system. On a customary basis, since the electrode potential is envisaged as the electric potential drop between M and S, the cell potential difference for system (1) is usually written as the electric potential difference between the two metallic terminals: EMi M1 (3) Since three interfaces are involved in cell (1), eqn.(3) can be rewritten as: E (M{ M) + (M S) + (S Mi) (4) Comparison of eqn. (4) with eqn. (2) shows that the identification of the absolute electrode potential with (M S) is not to be reconmended because it is conceptually misleading. Since M' and M are in electronic equilibrium, then (ref. 3): (4M ) = ('/F pr/F) (5) where the right hand side of eqn. (5) expresses the difference in chemical potential of electrons in the two electrode metals. Substitution of eqn.(5) into eqn.(4) gives: E = (p ii'/F) (E'q p'/F) (6) The two exoressions in brackets do not contain quantities pertaining to the other interfaces. They can thus be defined as single electrode potentials (Note d). Since eqn. (6) has been obtained with the two electrodes assembled into a cell, it is possible that terms common to both electrodes do not appear explicitly in eqn. (6) because they cancel out ultimately. The relationship between the truly absolute electrode potential and the single electrode potential in eqn.(6) can thus be written in the form (Note e) (ref. 5): EM(abs) = EM(r) + K (7) where K is a constant depending on the \"absolute\" reference system, and

1,205 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022116
2021193
2020370
2019631
2018558