Temperature dependence of the electrode potential of a cobalt-based redox couple in ionic liquid electrolytes for thermal energy harvesting

2016 ◽  
Vol 190 ◽  
pp. 205-218 ◽  
Author(s):  
Jiangjing He ◽  
Danah Al-Masri ◽  
Douglas R. MacFarlane ◽  
Jennifer M. Pringle
Keyword(s):  
Ionic Liquids ◽  
Waste Heat ◽  
Thermal Response ◽  
Thermodynamic Quantity ◽  
Redox System ◽  
Cell Performance ◽  
Redox Couple ◽  
Seebeck Coefficients ◽  
A Cell ◽  
Current Densities

Increasing the application of technologies for harvesting waste heat could make a significant contribution to sustainable energy production. Thermoelectrochemical cells are one such emerging technology, where the thermal response of a redox couple in an electrolyte is used to generate a potential difference across a cell when a temperature gradient exists. The unique physical properties of ionic liquids make them ideal for application as electrolytes in these devices. One of the keys to utilizing these media in efficient thermoelectrochemical cells is achieving high Seebeck coefficients, Se: the thermodynamic quantity that determines the magnitude of the voltage achieved per unit temperature difference. Here, we report the Se and cell performance of a cobalt-based redox couple in a range of different ionic liquids, to investigate the influence of the nature of the IL on the thermodynamics and cell performance of the redox system. The results reported include the highest Se to-date for an IL-based electrolyte. The effect of diluting the different ILs with propylene carbonate is also reported, which results in a significant increase in the output powers and current densities of the device.

scholarly journals Hydrogels Containing the Ferri/Ferrocyanide Redox Couple and Ionic Liquids for Thermocells

2019 ◽  
Vol 72 (2) ◽  
pp. 112 ◽  
Author(s):  
Matthew Russo ◽  
Holly Warren ◽  
Geoffrey M. Spinks ◽  
Douglas R. MacFarlane ◽  
Jennifer M. Pringle
Keyword(s):  
Mechanical Properties ◽  
Ionic Liquids ◽  
Solid State ◽  
Waste Heat ◽  
New Technology ◽  
Redox Couple ◽  
Low Grade ◽  
Aqueous Electrolytes ◽  
Hydrogel Network ◽  
Water Based

Thermoelectrochemical cells are a promising new technology for harvesting low-grade waste heat. The operation of these cells relies on a redox couple within an electrolyte, which is most commonly water-based, and improvement of these materials is a key aspect of the advancement of this technology. Here, we report the gelation of aqueous electrolytes containing the K3Fe(CN)6/K4Fe(CN)6 redox couple using a range of different polymers, including polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (Cmc), polyacrylamide (PAAm), and two commercial polyurethane-based polymers: HydroMed D640 and HydroSlip C. These polymers produce quasi-solid-state electrolytes with sufficient mechanical properties to prevent leakage, and allow improved device flexibility and safety. Furthermore, the incorporation of various ionic liquids within the optimized hydrogel network is investigated as a route to enhance the electrochemical and mechanical properties and thermal energy harvesting performance of the hydrogels.

The Effect of Solvent on the Seebeck Coefficient and Thermocell Performance of Cobalt Bipyridyl and Iron Ferri/Ferrocyanide Redox Couples

2019 ◽  
Vol 72 (9) ◽  
pp. 709 ◽  
Author(s):  
Abuzar Taheri ◽  
Douglas R. MacFarlane ◽  
Cristina Pozo-Gonzalo ◽  
Jennifer M. Pringle
Keyword(s):  
Organic Solvent ◽  
Seebeck Coefficient ◽  
Mixed Solvent ◽  
Waste Heat ◽  
Redox Couple ◽  
Seebeck Coefficients ◽  
Effect Of Solvent ◽  
Redox Couples ◽  
Ligand Interactions ◽  
Solvent Systems

The conversion of thermal energy to electricity using thermoelectrochemical cells (thermocells) is a developing approach to harvesting waste heat. The performance of a thermocell is highly dependent on the solvent used in the electrolyte, but the interplay of the various solvent effects is not yet well understood. Here, using the redox couples [Co(bpy)3][BF4]2/3 (bpy=2,2′-bipyridyl) and (Et4N)3/(NH4)4Fe(CN)6, which have been designed to allow dissolution in different solvent systems (aqueous, non-aqueous, and mixed solvent), the effect of solvent on the Seebeck coefficient (Se) and cell performance was studied. The highest Se for a cobalt-based redox couple measured thus far is reported. Different trends in the Seebeck coefficients of the two redox couples as a function of the ratio of organic solvent to water were observed. The cobalt redox couple produced a more positive Se in organic solvent than in water, whereas addition of water to organic solvent resulted in a more negative Se for Fe(CN)6 3−/4−. UV-vis and IR investigations of the redox couples indicate that Se is affected by changes in solvent–ligand interactions in the different solvent systems.

scholarly journals The Effect of Cell Compression and Cathode Pressure on Hydrogen Crossover in PEM Water Electrolysis

2021 ◽  
Author(s):  
Agate Martin ◽  
Patrick Trinke ◽  
Markus Stähler ◽  
Andrea Stähler ◽  
Fabian Scheepers ◽  
...  
Keyword(s):  
Mass Transport ◽  
Cell Voltage ◽  
Water Electrolysis ◽  
Material Design ◽  
Operating Conditions ◽  
Cell Performance ◽  
Membrane Electrode ◽  
Current Densities ◽  
Hydrogen Crossover ◽  
The Impact

Abstract Hydrogen crossover poses a crucial issue for polymer electrolyte membrane (PEM) water electrolysers in terms of safe operation and efficiency losses, especially at increased hydrogen pressures. Besides the impact of external operating conditions, the structural properties of the materials also influence the mass transport within the cell. In this study, we provide an analysis of the effect of elevated cathode pressures (up to 15 bar) in addition to increased compression of the membrane electrode assembly on hydrogen crossover and the cell performance, using thin Nafion 212 membranes and current densities up to 3.6 A cm-2. It is shown that a higher compression leads to increased mass transport overpotentials, although the overall cell performance is improved due to the decreased ohmic losses. The mass transport limitations also become visible in enhanced anodic hydrogen contents with increasing compression at high current densities. Moreover, increases in cathode pressure are amplifying the compression effect on hydrogen crossover and mass transport losses. The results indicate that the cell voltage should not be the only criterion for optimizing the system design, but that the material design has to be considered for the reduction of hydrogen crossover in PEM water electrolysis.

Electrochemistry of Neodymium in Phosphonium Ionic Liquids: The Influence of Cation, Water Content, and Mixed Anions

2020 ◽  
Vol 73 (11) ◽  
pp. 1080
Author(s):  
Laura Sanchez-Cupido ◽  
Jennifer M. Pringle ◽  
Amal Siriwardana ◽  
Cristina Pozo-Gonzalo ◽  
Maria Forsyth
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Electrochemical Behaviour ◽  
Critical Metals ◽  
Deposition Mechanism ◽  
Reduction Processes ◽  
Constant Potential ◽  
Current Densities ◽  
Environmentally Friendly Approach ◽  
Phosphonium Ionic Liquids

Electrodeposition using ionic liquids has emerged as an environmentally friendly approach to recover critical metals, such a neodymium. The investigation of ionic liquid chemistries and compositions is an important part of the move towards efficient neodymium recovery from end-of-life products that needs further research. Thus, in this paper we have investigated a series of phosphonium ionic liquids as potential electrolytic media. Anions such as bis(trifluoromethylsulfonyl)imide (TFSI), dicyanamide (DCA), and triflate (TfO) have been investigated, in combination with short- and long-alkyl-chain phosphonium cations. The work here suggests that [TFSI]– is one of the most promising anions for successful deposition of Nd and that water plays an important role. In contrast, electrochemical behaviour was significantly hindered in the case of DCA ionic liquid, most likely owing to strong coordination between [DCA]– and Nd3+. Mixtures of anions, [TfO]– and [TFSI]–, have also been investigated in this work, resulting in two reduction processes that could be related to a different deposition mechanism involving two steps, as observed in the case of dysprosium or, alternatively, different coordination environments that have distinct deposition potentials. Additionally, we investigated the influence of electrode substrates – glassy carbon and copper. Cu electrodes resulted in the largest current densities and thus were used for subsequent electrodeposition at constant potential. These findings are valuable for optimising the deposition of Nd in order to develop more efficient and inexpensive recycling technologies for rare earth metals.

Spray-on thermoelectric energy harvester

MRS Advances ◽  
2018 ◽  
Vol 4 (15) ◽  
pp. 851-855 ◽  
Author(s):  
Robert E. Peale ◽  
Seth Calhoun ◽  
Nagendra Dhakal ◽  
Isaiah O. Oladeji ◽  
Francisco J. González
Keyword(s):  
Thin Films ◽  
Power Generation ◽  
Energy Harvester ◽  
Waste Heat ◽  
Spray Deposition ◽  
Electrical Energy ◽  
Seebeck Coefficients ◽  
Thermoelectric Energy ◽  
P Type ◽  
Energy From Waste

AbstractThermoelectric (TE) thin films have promise for harvesting electrical energy from waste heat. We demonstrate TE materials and thermocouples deposited by aqueous spray deposition on glass. The n-type material was CdO doped with Mn and Sn. Two p-type materials were investigated, namely PbS with co-growth of CdS and doped with Na and Na2CoO4. Seebeck coefficients, resistivity, and power generation for thermocouples were characterized.

Electrode Kinetics of Oxygen/Superoxide Ion Redox Couple in Some Amide-Type Ionic Liquids

2013 ◽  
Vol 50 (11) ◽  
pp. 159-166 ◽  
Author(s):  
T. Nakagawa ◽  
Y. Katayama ◽  
T. Miura
Keyword(s):  
Ionic Liquids ◽  
Redox Couple ◽  
Electrode Kinetics ◽  
Superoxide Ion ◽  
Kinetics Of

Magneto-Seebeck tunneling on the atomic scale

Science ◽  
2019 ◽  
Vol 363 (6431) ◽  
pp. 1065-1067 ◽  
Author(s):  
Cody Friesen ◽  
Hermann Osterhage ◽  
Johannes Friedlein ◽  
Anika Schlenhoff ◽  
Roland Wiesendanger ◽  
...  
Keyword(s):  
Waste Heat ◽  
Magnetic Tunnel Junction ◽  
Thermal Control ◽  
Atomic Scale ◽  
Polarized Electrons ◽  
Seebeck Coefficients ◽  
Spin Polarized ◽  
Close Proximity ◽  
Fundamental Process ◽  
Spin Texture

The tunneling of spin-polarized electrons across a magnetic tunnel junction driven by a temperature gradient is a fundamental process for the thermal control of electron spin transport. We experimentally investigated the atomic-scale details of this magneto-Seebeck tunneling by placing a magnetic probe tip in close proximity to a magnetic sample at cryogenic temperature, with a vacuum as the tunneling barrier. Heating the tip and measuring the thermopower of the junction while scanning across the spin texture of the sample lead to spin-resolved Seebeck coefficients that can be mapped at atomic-scale lateral resolution. We propose a spin detector for spintronics applications that is driven solely by waste heat, using magneto-Seebeck tunneling to convert spin information into a voltage that can be used for further data processing.

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