Hot Electrode Research Articles

Influence of different factors on gap breakdown process with hot electrode and high temperature gas medium in low voltage circuit breaker chamber based on particle-in-cell/Monte-Carlo collision simulation

Different factors such as gas composition inside the low voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the effects of non-parallel electrode structure, gas temperature and pressure, electrode temperature, and gap distance on gap breakdown of hot electrode under high temperature gas conditions were studied, for which a particle-in-cell/Monte-Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization and other effects, and simulation studies have been conducted. The simulation results show that the increase in gap gas temperature, the decrease in air pressure, and the increase in electrode temperature will lead to the gap breakdown more easily. With the increase in the gap length, the breakdown voltage increases, but the average electric field intensity required for breakdown decreases. In the non-parallel electrode structure, the breakdown occurs first at the position with the shortest gap distance, then the cathode sheath forms and extends along the electrode surface to other areas, and finally, the entire gap breaks down.

Carbon-Coated MOF-Derived Porous SnPS3 Core-Shell Structure as Superior Anode for Sodium-Ion Batteries.

Metal thiophosphites have recently emerged as a hot electrode material system for sodium-ion batteries because of their large theoretical capacity. Nevertheless, the sluggish electrochemical reaction kinetics and drastic volume expansion induced by the low conductivity and inherent conversion-alloying reaction mechanism, require urgent resolution. Herein, a distinctive porous core-shell structure, denoted as SnPS3@C, is controllably synthesized by synchronously phosphor-sulfurizing resorcinol-formaldehyde-coated tin metal-organic framework cubes. Thanks to the 3Dporous structure, the ion diffusion kinetics are accelerated. In addition, SnPS3@C features a tough protective carbon layer, which improves the electrochemical activity and reduces the polarization. As expected, the as-prepared SnPS3@C electrode exhibits superior electrochemical performance compared to pure SnPS3, including excellent rate capability (1342.4 and 731.1mAhg-1 at 0.1 and 4Ag-1, respectively), and impressive long-term cycling stability (97.9% capacity retention after 1000 cycles at 1Ag-1). Moreover, the sodium storage mechanism is thoroughly studied by in-situ and ex-situ characterizations. This work offers an innovative approach to enhance the energy storage performance of metal thiophosphite materials through meticulous structural design, including the introduction of porous characteristics and core-shell structures.

Hot electrodes, cool reduction.

Hot electrodes, cool reduction.

Water, Not Salt, Causes Most of the Seebeck Effect of Nonisothermal Aqueous Electrolytes.

A temperature difference between two electrolyte-immersed electrodes often yields a voltage Δψ between them. This electrolyte Seebeck effect is usually explained by cations and anions flowing differently in thermal gradients. However, using molecular simulations, we found almost the same Δψ for cells filled with pure water as with aqueous alkali halides. Water layering and orientation near polarizable electrodes cause a large temperature-dependent potential drop χ there. The difference in χ of hot and cold electrodes captures most of the thermovoltage, Δψ≈χ_{hot}-χ_{cold}.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

Experimental demonstration of scalability in a cavity-free planar silicon-integrated thermoelectric device

We demonstrate the scalability of cavity-free planar integrated thermoelectric (TE) devices using silicon nanowires (Si-NWs), where miniaturizing the thermoelement by shortening the Si-NWs improves the areal power density. Shortening the Si-NW length decreases the temperature difference between the Si-NW ends and the open-circuit voltage. Meanwhile, the integrated number density of the thermoelement is increased by shortening the Si-NW length, thereby preserving the total electrical resistance. Bileg devices comprising both n- and p-type Si-NWs exhibited superior performance compared to unileg devices comprising only n-type Si-NWs. In unileg devices, the hot and cold electrodes in the adjacent thermoelements are interconnected through metal wiring, which leaks heat, resulting in a lowering of the temperature difference between the Si-NW ends. This study yields structural design guidelines for planar-integrated TE devices using Si-NWs.

Concentration gradient effect in liquid thermoelectric device composed of organic-solvent-added aqueous solution containing K4[Fe(CN)6]/K3[Fe(CN)6

A liquid thermoelectric conversion device (LTE), which has a simple device structure composed of low-cost materials, is attracting attention. Here, we investigated the additive effect of methanol (MeOH), acetone, and tetrahydrofuran (THF) on an LTE composed of a K4[Fe(CN)6]/K3[Fe(CN)6] aqueous solution. We ascribed to the enhancement of the thermal voltage V and electrochemical Seebeck coefficient α to precipitation of K4[Fe(CN)6] and resultant concentration gradient of [Fe(CN)6]3− between the hot and cold electrodes. The enhancement of V and α is quantitatively reproduced by the concentration gradient model incorporating experimentally-obtained solubility s(T) of K4[Fe(CN)6]. We further demonstrated that precipitation enhances the maximum power by as much as 152% in a MeOH-added LTE composed of 0.35 M K4[Fe(CN)6]/K3[Fe(CN)6] aqueous solution at ΔT = 10 K.

Thomson effect in thermionic refrigeration: Enhanced performance of graphene/2D-semiconductor/graphene heterostructure cooler

Two-dimensional (2D) materials and their heterostructures have been widely explored for high-performance energy conversion applications. The Thomson effect—a higher order transport process—plays an important role in thermoelectric devices, yet its effect on the performance of thermionic devices remains unknown thus far. Here, we investigate the performance of thermionic refrigeration in vertically stacked heterostructure (VHS) and laterally stitched heterointerface (LHS) composed of a graphene and a 2D semiconductor (i.e., MoS2 and WSe2) in the presence of the Thomson effect. Using a temperature-dependent Seebeck coefficient, we derived the analytical expressions of the cooling efficiency and the effective ZT. We shall show that the Thomson effect improves the coefficient of performance (COP) by up to 20%, particularly, in the case where the temperature difference between the cold and the hot electrodes is large. However, the Carnot efficiency decreases with the temperature difference. The overall COP is reduced by the Thomson effect. We calculate the COP in graphene/MoS2/graphene and graphene/WSe2/graphene VHS and LHS devices. We show that the LHS composed of WSe2 significantly outperforms the VHS and MoS2 counterpart. These findings provide an understanding of thermionic processes in the higher-order transport regime and shall offer insights into the design of novel 2D material heterostructure thermionic energy converters.

A Novel Gel Thermoelectric Chemical Cell for Harvesting Low-Grade Heat Energy.

The use of gel thermoelectric chemical cells to capture low-grade heat for conversion to electricity is an attractive approach. However, there are few studies on whether the distribution of redox species in the electrolyte has an effect on the performance of cells. Herein, this concern was discussed by constructing a novel gel thermoelectric chemical cell (Cu-C-cg). Using cellulose-like rice paper as a separator, a concentration gradient of electrolyte was carefully constructed, so that the concentration of potassium ferrocyanide gradually decreased from the hot electrode to the cold electrode while the concentration of potassium ferricyanide gradually increased. Through electrochemical measurement and analysis, it was found that the thermoelectric performance of this cell outperformed the cell without electrolyte concentration gradients. Meanwhile, this performance could be enhanced by the use of asymmetric electrodes composed of copper foil and carbon electrodes. After optimizing the conditions, the open-circuit voltage, output power, and Seebeck coefficient of the Cu-C-cg cell at 12 K temperature difference were 0.450 V, 183 μW, and 7.82 mV K-1 , respectively. This work not only provides a novel idea in gel-based cell design but also an excellent thermoelectric chemical cell.

Ignition of an ionic liquid dual-mode monopropellant using a microwave plasma torch

The blend of hydroxylammonium nitrate (HAN) and imidazole-based ionic liquid has shown good feasibility in chemical and electric dual-mode green space propulsion. As conventional catalyst-driven ignition faces challenges arising from long preheat delay and catalyst failure, this work designs a novel ignition actuator using a microwave plasma torch. The precise tuning of the ¼-λ resonant cavity and improvement in the quality factor (QF) of the microwave igniter make the device efficient and thus allow the propellant to be ignited at a power of approximately 100 W. In the present reduced test rig, the maximum fuel flow rate corresponds to 0.1 N chemical thrusters, and the plasma-assisted ignition is mainly attributed to thermal and kinetic effects. The temperature of the actuator and the plasma torch is investigated by infrared thermometry and spectral fitting of excited molecule nitrogen, respectively. First, the hot electrode tube helps evaporate water molecules and accelerate the liquid jet through rapid gas expansion. Then, the ionic liquid quickly decomposes to small species when the flow reaches the torch with a nitrogen vibrational temperature above 4000 K and rotational temperature above 2000 K. Meanwhile, the nonequilibrium plasma-excited species enhance the combustion of gaseous intermediates by direct impact dissociation, where the OH radical profile is visualized using the planar laser-induced fluorescence technique. In addition, the copper atoms released by plasma erosion are expected to exhibit a significant catalytic effect on ionic liquid decomposition, which is a critical step in controlling the overall reaction rate. It is also noted that such mild erosion does not affect the multi-start operations during the firing test that lasts for at least 30 min.

Using hydropower turbine discharge as a complementary spillway

Spillways are very important dam safety devices that can discharge large amounts of water to prevent over-topping a dam. However, spillways are expensive to build and have operational issues. This paper is a report from a test of a system capable of discharging the full turbine flow even in the absence of an external power grid absorbing the electrical power. Instead the power is dissipated in a local load. The scope of the tests is to verify the use of the discharge capacity of the turbine under continuous operation as spillway flow for emergency discharge from a Hydropower reservoir. A dumpload consisting of a hot water electrode boiler cooled by water taken from the turbine spiral case was used as a local load. The results show long-term stability of using a local load and turbine discharge as an electrical alternative to building additional traditional spillways to increase spillway capacity from a hydropower reservoir.

Thermally Chargeable Ammonium‐Ion Capacitor for Energy Storage and Low‐Grade Heat Harvesting

AbstractHarvesting heat from the low‐grade heat (below 100 °C) into electricity has the signification to enhance the utilization of energy and lower carbon emissions by a simple device. Herein we demonstrate a thermally chargeable ammonium ion capacitor (TAIC) by employing graphene‐polyimide (rGO‐PI) synthesized through polycondensation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride and ethylenediamine as cold electrode, N‐doped hollow carbon nanofibers as hot electrode to directly convert waste heat into electricity. Combining thermodiffusion effect of electrolyte with thermogalvanic effect of a redox couple (−C=O/−C−O−NH4+), as‐assembled TAIC can deliver a high output voltage of 624 mV, power density of 82 μW cm−2 and average Seebeck coefficient of 9.07 mV K−1 at temperature difference of 45 K. Meanwhile, with the introduction of polyacrylamide‐polyacrylic acid‐based gel electrolyte, the assembled flexible device can well serve in various bending states, and the power density can attain a satisfying value of 1.92 μW cm−2. This quasi‐solid‐state TAIC shows great potential as one promising candidate for high value‐added conversion from low‐grade heat into electricity as well as wearable applications.

Wearable Photo-Thermo-Electrochemical Cells (PTECs) Harvesting Solar Energy.

Solar induced thermal energy is a vital heat source supplementing body heat to realize thermo-to-electric energy supply for wearable electronics. Thermo-electrochemical cells, compared to the widely investigated thermoelectric generators, show greater potential in wearable applications due to the higher voltage output from low-grade heat and the increased option range of cheap and flexible electrode/electrolyte materials. A wearable photo-thermo-electrochemical cell (PTEC) is first fabricated here through the introduction of a polymer-based flexible photothermal film as a solar-absorber and hot electrode, followed by a systematic investigation of wearable device design. The as-prepared PTEC single device shows outstanding output voltage and current density of 15.0mV and 10.8Am-2 and 7.1mV and 8.57Am-2 , for the device employing p-type and n-type gel electrolytes, respectively. Benefiting from the equivalent performance in current density, a series connection containing 18pairs of p-n PTEC devices is effectively made, which can harvest solar energy and charge supercapacitors to above 250mV (1sun solar illumination). Meanwhile, a watch-strap shaped flexible PTEC (eight p-n pairs) that can be worn on a wrist is fabricated and the realized voltage above 150mV under light shows the potential for use in wearable applications.

Thermoelectrochemical Cells Based on Ferricyanide/Ferrocyanide/Guanidinium: Application and Challenges.

Ferricyanide/ferrocyanide/guanidinium-based thermoelectrochemical cells have been investigated under different loading conditions in this work. Compared with ferricyanide/ferrocyanide-based devices, the device with guanidinium-added electrolytes shows higher power and energy densities. We observed that the enhanced performance is not due to the ionic Seebeck effect of guanidinium but because of the configuration entropy change resulting from the selective binding of Gdm+ to Fe(CN)64-. However, the device with guanidinium-added electrolyte does not show steady-state operation. The two possible reasons include (1) the difficult diffusion of Fe(CN)63- into the crystal layer of (Gdm+)n[Fe(CN)64-] at the hot electrode and (2) the difficult precipitation of (Gdm+)n[Fe(CN)64-] formed at the cold side upon the binding of the reduced Fe(CN)64- with Gdm+. Nevertheless, the performance recovers once the device is disconnected from the external loading. Due to the high thermopower after adding guanidinium, we successfully fabricate self-powered sensors by connecting four flexible cells in series. The sensors can transfer humidity, temperature, and air pressure data wirelessly using body heat. Therefore, ferricyanide/ferrocyanide/guanidinium is a promising electrolyte material for applications of low-grade energy harvesting.

Real-Time Tunable Dynamic Range for Calibration-Free Biomolecular Measurements with a Temperature-Modulated Electrochemical Aptamer-Based Sensor in an Unprocessed Actual Sample.

The sensing technologies for monitoring molecular analytes in biological fluids with high frequency and in real time could enable a broad range of applications in personalized healthcare and clinical diagnosis. However, due to the limited dynamic range (less than 81-fold), real-time analysis of biomolecular concentration varying over multiple orders of magnitude is a severe challenge faced by this class of analytical platforms. For the first time, we describe here that temperature-modulated electrochemical aptamer-based sensors with a dynamically adjustable calibration-free detection window could enable continuous, real-time, and accurate response for the several-hundredfold target concentration changes in unprocessed actual samples. Specifically, we could regulate the electrode surface temperature of sensors to obtain the corresponding dynamic range because of the temperature-dependent affinity variations. This temperature modulation method relies on an alternate hot and cold electrode reported by our group, whose surface could actively be heated and cooled without the need for altering ambient temperature, thus likewise applying for the flowing system. We then performed dual-frequency calibration-free measurements at different interface temperatures, thus achieving an extended detection window from 25 to 2500 μM for procaine in undiluted urine, 1-500 μM for adenosine triphosphate, and 5-2000 μM for adenosine in undiluted serum. The resulting sensor architecture could drastically expand the real-time response range accessible to these continuous, reagent-less biosensors.

Carbon Particle-Doped Polymer Layers on Metals as Chemically and Mechanically Resistant Composite Electrodes for Hot Electron Electrochemistry

This paper presents a simple and inexpensive method to fabricate chemically and mechanically resistant hot electron-emitting composite electrodes on reusable substrates. In this study, the hot electron emitting composite electrodes were manufactured by doping a polymer, nylon 6,6, with few different brands of carbon particles (graphite, carbon black) and by coating metal substrates with the aforementioned composite ink layers with different carbon-polymer mass fractions. The optimal mass fractions in these composite layers allowed to fabricate composite electrodes that can inject hot electrons into aqueous electrolyte solutions and clearly generate hot electron-induced electrochemiluminescence (HECL). An aromatic terbium (III) chelate was used as a probe that is known not to be excited on the basis of traditional electrochemistry but to be efficiently electrically excited in the presence of hydrated electrons and during injection of hot electrons into aqueous solution. Thus, the presence of hot, pre-hydrated or hydrated electrons at the close vicinity of the composite electrode surface were monitored by HECL. The study shows that the extreme pH conditions could not damage the present composite electrodes. These low-cost, simplified and robust composite electrodes thus demonstrate that they can be used in HECL bioaffinity assays and other applications of hot electron electrochemistry.

Investigation of Si-based thermoelectrochemical cells (TECs) towards semiconductor fabrication and processing

Thermoelectrochemical cells (TECs) are an alternative with potential for micro-power generator applications but is rarely fabricated using semiconductor processes or micro-fabrication technology. This study initiates fabrication of a Si-based TEC cell device using micro-fabrication technology. The iodide/triiodide poly(vinyl alcohol) hydrogel polymer electrolyte, and citric acid as supporting electrolyte, is selected as the TEC material. A platinum electrode sputtered on a silicon substrate is used as the hot and cold electrode. The TEC voltage generation that is based on Soret diffusion and the Seebeck effect shows good repeatability and stability. The magnitude of the power density shows dependence on the device electrode separation and temperature difference. At 10 mm electrode separation and a temperature difference of 30 K, the Si substrate TEC is able to produce 310 µW m−2; thus, it shows high potential as a low heat waste Si-based TEC power generator.

Гибридная система, преобразующая солнечную энергию в электрическую

The article discusses a mathematical model of a hybrid system that combines photovoltaic and thermoelectric methods for converting concentrated solar energy into electrical energy. The specified mathematical model makes it possible to determine the temperatures of the photovoltaic module, as well as the temperature of the electrodes of the thermoelectric generator module. Optimal operating conditions have been determined for the hybrid system, taking into account the thermal contact resistance at the hot and cold sides of the thermoelectric generator. The simulation proceeded from the fact that only part of the absorbed solar radiation is converted into electricity due to the photoelectric effect, some part is lost due to radiation and convection from the upper surface of the photovoltaic module into the environment, and the rest is transferred to a thermoelectric generator connected to the lower part. photovoltaic module. A thermoelectric generator converts some of the thermal energy it receives from the photovoltaic module into electricity through the Seebeck effect, but most of it goes to the cooling system. The conversion of heat into electrical energy was based on the well-known Seebeck and Peltier effects. Along with these effects, such effects were taken into account as the formation of Joule heat due to the presence of electric current in the thermoelectric generator, Fourier thermal conductivity, as a consequence of the appearance of a temperature gradient in the transitions of a thermoelectric generator and Thomson heat, which arises both due to the presence of a temperature gradient, and electric current. The resulting model of the hybrid system makes it possible to study the effect of changing the temperature difference between the hot and cold electrodes of the thermoelectric generator and the resistance of the external circuit on the performance of the hybrid system. The model also allows the determination of the optimal operating conditions for the hybrid system, taking into account the thermal contact resistance on the hot and cold sides of the thermoelectric generator.

Hybrid thermoelectrochemical and concentration cells for harvesting low-grade waste heat

Thermoelectrochemical cells (TECs) are promising platforms for thermal energy conversion. However, their widespread use is limited because of their low Seebeck coefficient and low conversion efficiency. We demonstrate a hybrid thermoelectrochemical and concentration cell based on carbonate solvents with a I3−/I− redox couple (referred to as i-TCC), which outperforms the current best n-type TEC employing an aqueous Fe3+/2+ redox couple. As the temperature of the hot side of i-TCC increases above 40 °C, dimethyl carbonate solvent reacts with iodide anions to form a porous Li2CO3-matrix near the hot electrode, which sustains long-lasting iodide-concentration gradient across the cell. The thermally driven concentration difference boosts the performance of the TEC to yield a remarkably high Seebeck coefficient (+7.7 mV K−1), figure of merit (ZT = 0.114), and Carnot efficiency (5.2%) for a temperature difference of 35 °C (25 °C and 60 °C for cold and hot temperatures, respectively). i-TCC demonstrated here thus provides a new perspective in harvesting low-grade waste heat.

Double-network thermocells with extraordinary toughness and boosted power density for continuous heat harvesting

Double-network thermocells with extraordinary toughness and boosted power density for continuous heat harvesting