Calorimetric study of an electrochemical reduction

Turner, Peter; Pritchard, H. O.

doi:10.1139/v78-231

Cited by 7 publications

(2 citation statements)

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“…The history of electrochemical calorimetry illustrates that this research has generally been a neglected scientific topic despite the many possible calorimetric applications in electrochemical research [1][2][3][4][5]. An excellent test for open isoperibolic calorimetric cells is the determination of the enthalpy change for the electrolysis of heavy water (D2O).…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Miles¹

2019

Preprint

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Equations developed for isoperibolic electrochemical calorimetry were tested for the electrolysis of D2O in an open calorimetric cell. The derivatives of these equations gave correct values within the experimental error range for the important rate of change of the cell temperature with time (dT/dt). In addition, these calorimetric equations were also tested directly in determining the enthalpy change (ΔH) for the D2O electrolysis reaction. The mean experimental value at 298.15 K was ΔH = 294.4 ± 0.3 kJ/mole. This compares favorably (within 0.10%) with the literature value of ΔH = 294.600 kJ/mole. The accuracy of these ΔH measurements could be even further improved by more accurate cell voltage and cell temperature measurement. <br>

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Section: Introductionmentioning

confidence: 99%

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Miles¹

2019

Preprint

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“…When it is possible to determine the reversible heat, this provides valuable information on the change in thermodynamic state of the system. The reversible heat can for example correspond to the enthalpy changes due to the electrochemical processes [49,50] or to the entropic heat from batteries, in agreement with the temperature dependence of their open circuit voltage [51]. For supercapacitors, the reversible heat has been interpreted in different ways, as the entropic heat from the confinement of ions into the pores of the electrodes [28], or as changes in the entropic part of the grand potential energy [31,32], or as due to several entropic and enthalpic contributions because of mixing as well as electrical and steric interactions of the ions [27,33,34], or as due to nonzero potential energy of the ions in the pore; see Chapter 3.…”

Section: Introductionmentioning

confidence: 99%

Calorimetry of Capacitive Porous Carbon Electrodes in Aqueous Media

Vos¹

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Chapter 1 contains an overview of the background of this thesis. Porous carbon electrodes and their applications are introduced, followed by a discussion of the Electric Double Layer (EDL) in porous carbon electrodes. Then, experimental work on the thermodynamics of the EDL in porous electrodes is presented. This Chapter ends with a brief description of the electrochemical calorimetry setup. In Chapter 2, the electrochemical calorimetry setup is examined in more detail. The cell contained an aqueous electrolyte solution and three electrodes. The potential of the working electrode (WE) was applied with respect to the reference electrode (RE), and the current was measured between WE and counter electrode (CE). Behind the WE, a heat flux sensor (HFS) measured the heat flow coming from the WE during the (dis)charging of the EDL. The heat was calibrated on the Joule heat produced in a full charge-discharge cycle. We us the setup to measure the heat of (dis)charging the WE as a function of the potential applied to the electrode. Chapter 3 describes how the setup was used to determine the potential-dependent internal energy of porous carbon electrodes in aqueous solutions of different salts. Changes were calculated from the (electrical) work performed on the system and the heat released or absorbed by the system. The energy changes consist of two contributions, which respectively scaled linearly and quadratically with applied potential. The linear contribution was ascribed to the attraction of ions to the surface of the pores, given by the number of adsorbed ions times a fixed attraction energy per ion. The quadratic contribution was slightly smaller than expected for a parallel plate capacitor of the same capacitance, which we interpreted in terms of the average electric potential experienced by ions inside the pores. Chapter 4 demonstrated that the formula found in Chapter 3 can also explain the time-dependent heat production. The charging rate was varied by changing the amount of time taken to build up the applied potential linearly until the final potential was reached. Using four constant parameters, both the reversible and irreversible heat production rates could be explained. We verified that the reversible heat was the same regardless of the charging rate. Agreement between model and experiment was only semi-quantitative, which we attributed to a time dependence of the electric current more complicated than mono-exponential decay. In Chapter 5 we analyzed the time dependence of the current for the (dis)charging of porous carbon electrodes in 1M solutions. The rate of exponential decay of the current was initially determined by the RC time and later by a distribution of time constants, which we attributed to polydispersity of the pores. The late-time current decay was slower at cathodic than at anodic potentials, but we argued that this was not because of the different diffusion coefficients of the cations and anions, which were nearly identical for KCl. Instead, the potential-dependent dynamics were discussed in terms of the different capacitance of the electrode in the cathodic and anodic ranges, resulting from specific ion adsorption.

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Oxo‐Entity‐Controlled Diastereomer Peculiarity of Rhenium(V) Complexes ReOX₂(P~O)py [X = Cl, Br, I; P~O = (OCMe₂CMe₂O)POCMe₂CMe₂O(1–); py = pyridine]: Synthesis and Molecular and Crystal Structural Characterization

et al. 2005

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-6-15] complexes can be obtained concomitantly, while for X = I only a trans complex can be afforded. Molecular structures were characterized using NMR IR and UV/Vis spectroscopic methods with the aid of DFT computational analysis and were ultimately corroborated by the single-crystal X-ray diffraction method. These analyses revealed that the most stable diastereomers involve an O=Re(-O~P) oxo arrangement in an axial disposition reinforced with a phosphorus ligating atom mutually cis due to extensive π-bonding both for chiral cis

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Calorimetric study of an electrochemical reduction

Abstract: The aqueous trichloroacetate ion is reduced irreversibly and with unit current efficiency to the dichloroacetate ion. From the total energy release observed when this process is carried out inside a calorimeter, it is possible to deduce the enthalpy change for the reduction reaction.

Cited by 7 publications

References 3 publications

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Calorimetry of Capacitive Porous Carbon Electrodes in Aqueous Media

Oxo‐Entity‐Controlled Diastereomer Peculiarity of Rhenium(V) Complexes ReOX₂(P~O)py [X = Cl, Br, I; P~O = (OCMe₂CMe₂O)POCMe₂CMe₂O(1–); py = pyridine]: Synthesis and Molecular and Crystal Structural Characterization

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Calorimetric study of an electrochemical reduction

Abstract: The aqueous trichloroacetate ion is reduced irreversibly and with unit current efficiency to the dichloroacetate ion. From the total energy release observed when this process is carried out inside a calorimeter, it is possible to deduce the enthalpy change for the reduction reaction.

Cited by 7 publications

References 3 publications

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Electrochemical Isoperibolic Calorimetry for D2O Electrolysis

Calorimetry of Capacitive Porous Carbon Electrodes in Aqueous Media

Oxo‐Entity‐Controlled Diastereomer Peculiarity of Rhenium(V) Complexes ReOX2(P~O)py [X = Cl, Br, I; P~O = (OCMe2CMe2O)POCMe2CMe2O(1–); py = pyridine]: Synthesis and Molecular and Crystal Structural Characterization

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Oxo‐Entity‐Controlled Diastereomer Peculiarity of Rhenium(V) Complexes ReOX₂(P~O)py [X = Cl, Br, I; P~O = (OCMe₂CMe₂O)POCMe₂CMe₂O(1–); py = pyridine]: Synthesis and Molecular and Crystal Structural Characterization