Proton Current Density Research Articles

Investigation on Effect of Reducing Cathode Pt-Loading on Ohmic Overpotential in Catalyst Layer

To reduce the use of precious metals in polymer electrolyte fuel cells (PEFCs), it is necessary not only to develop high activity catalysts but also to design optimal membrane-electrode-assembly (MEA) structure. In the past two decades, it becomes well known that oxygen transport resistance near the catalyst surface is a critical issue when reducing cathode catalyst loading due to concentration of oxygen flux on a small catalyst surface area [1-3]. On the other hand, as well as the case of oxygen flux, small catalyst surface area also increases proton current density near the catalyst particles, which can cause larger overpotential due to proton migration (ohmic overpotential). This is likely to be more important for recent-trend catalyst layer structure which avoids direct coating of ionomer on the catalyst to improve catalyst activity, e.g., employing porous carbon for the catalyst support [4-5]. Such a structure of catalyst layer can cause large resistance especially at a low humidity condition where no proton conduction path through water film exists. In this study, we investigated the effect of reducing catalyst loading on ohmic overpotential in catalyst layers to discuss the impact of local proton resistance quantitatively.MEA samples were fabricated by a pulse spray method using commercial catalyst supported on porous carbon and solid carbon (TEC10E50E and TEC10V30E, TANAKA Kikinzoku Kogyo K.K.), respectively. Nafion D2020 was employed as an ionomer, and ionomer-carbon weight ratio (I/C) was varied. For each specification, MEAs with different Pt-loading on cathode were prepared with the value of ~0.05 mgPt/cm2 and ~0.2 mgPt/cm2, respectively. GORE-SELECT Membrane M788.12 was employed as a membrane. Humidity dependence of the cell performance was evaluated at a cell temperature of 80°C. To evaluate ohmic overpotential within the catalyst layer, the performance was evaluated varying oxygen partial pressure (p O2). Structures of catalyst layers were analyzed using a scanning electron microscope and a transmission electron microscope.Some of the evaluation results are shown below. Figure 1 shows the humidity dependence of the performance of the MEAs with different cathode catalyst loading at a high p O2 condition of 100 kPa, where the oxygen concentration overpotential can be ignored in a wide current density range. The performance of the low Pt-loading MEA shows large humidity dependence. One of the reasons of this is humidity dependence of the catalyst activity reflecting the humidity dependence of the electrochemical surface area. Additionally, the apparent Tafel slope is larger at lower humidity, which indicates the contribution of the ohmic overpotential at such a low current density. Figure 2 shows the performance at various p O2, where the current density is normalized by p O2. Assuming a reaction order equal to 1 for the oxygen reduction reaction, this p O2-normalized current should be identical at a certain electrode potential for the variation of p O2 when the proton resistance is enough small and spatial reaction-distribution within the catalyst layer can be assumed homogeneous. For the high humidity performance of solid carbon MEA presented in Fig. 2 (c), the p O2 normalized performance is almost identical for all the p O2 conditions, which supports that ohmic overpotential is not significant in this current density range. On the other hand, at the relative humidity of 40%, the normalized performance shows large deviations, which reflect the proton resistance contribution, for all of the samples. The low Pt-loading samples show relatively larger deviations, especially for the porous carbon MEA, which indicates the effect of the local proton resistance. Origin of these proton resistance will be discussed in conjunction with the structures of the catalyst support and catalyst layer.The results suggest that the local proton resistance in the vicinity of the catalyst particles causes overpotential large enough to suppress the cell performance. To investigate local proton transport character of developed catalyst, it should be useful to evaluate Pt-loading dependence of the ohmic overpotential.

Numerical Analysis of Humidification Condition Effects on Protonic Ceramic Fuel Cell Performance Considering Concentration Overpotential

Protonic ceramic fuel cells (PCFCs) show relatively high performance at intermediate temperature range (400–600 °C) due to high proton conductivity in electrolyte. However, besides proton, other charges such as electron hole and oxygen vacancy can also be conductive in PCFCs. Especially, the hole conductivity will induce a hole current leakage so that current efficiency and power density will decrease. Besides the operating temperature, the conductivities of proton and hole are also strongly affected by the partial pressures of steam and oxygen in the PCFC [1,2]. Higher steam partial pressure leads higher proton conductivity, so that a higher power density can be expected. However, other influences such as concentration overpotential may be non-negligible. Furthermore, the proton and hole current density are affected by defect concentrations differences between two surfaces of the electrolyte membrane. Numerical simulation method is powerful tool for dealing with the complicated conditions in a PCFC mentioned above.In the present study, the influences of steam partial pressure on a BaZr0.8Yb0.2O3− δ (BZYb20) electrolyte are investigated. Specifically, to reveal the currents induced by the electrostatic potential and gas concentrations, Nernst-Planck model is selected. To relatively obviously reveal the steam concentration influences on the PCFC performances, low (3%) and high (69%) humidification conditions of H2 fuel gas are adopted. The results in Fig. 1(a) and 1(b) show the simulation and experimental current-voltage characteristics under 3% and 69% humidification conditions, respectively. The green solid and dotted lines are external and proton current densities considering concentration overpotential influence, respectively. The blue lines express external current density when no concentration overpotential in the numerical model. The red circles are the measured data. At low steam partial pressure, the simulation results well reproduced the experimental data without concentration overpotential consideration. However, an obvious deviation was found between simulation and experimental results when neglecting concentration overpotential in the simulation model. The performances such as open circuit voltage (OCV) and hole current leakage (difference between proton and external current density) are influenced by the steam partial pressure.

Effect of cooling surface temperature difference on the performance of high-temperature PEMFCs

Internal temperature distribution of the high-temperature proton exchange membrane fuel cell (HT-PEMFC) is affected by the cooling temperature, heat generation and reactant gas flow. Reasonable temperature control is helpful to improve the fuel cell performance and durability. In this work, a three-dimensional model that couples the reactant flows, species transport, heat transfer, charge transfer, and electrochemical reaction, was developed to simulate the HT-PEMFC operation. A solid mechanics model was established to analyze the stress distribution of the fuel cell. The polarization curves, distributions of temperature, membrane proton conductivity, current density and stress are investigated for different cooling surface temperature. Furthermore, the effect of assembly temperature on the stress of phosphoric acid-doped polybenzimidazole (PBI) membrane is discussed. Results reveals that the peak power density and uniformity of current density decrease with the increase of cooling surface temperature difference. The peak power density decreases by 9.14% when the temperature difference increases from 0 K to 40 K. The cooling surface temperature difference of less than 10 K and the voltage range in 0.5–0.7 V can achieve better current density uniformity and smaller current density change rate. In addition, the membrane in fuel cell has the highest stress, and increasing the assembly temperature is helpful to reduce the membrane stress. When the assembly temperature increases from 293.15 K to 343.15 K, the max and min compressive stresses in membrane in-plane decrease from 39.436 MPa to 31.416 MPa–24.934 MPa and 17.369 MPa at the temperature difference of 30 K, which decreases by 36.77% and 44.7%, respectively.

Ultra-high dose rate dosimetry for pre-clinical experiments with mm-small proton fields

PurposeTo characterize an experimental setup for ultra-high dose rate (UHDR) proton irradiations, and to address the challenges of dosimetry in millimetre-small pencil proton beams. MethodsAt the PSI Gantry 1, high-energy transmission pencil beams can be delivered to biological samples and detectors up to a maximum local dose rate of ∼9000 Gy/s. In the presented setup, a Faraday cup is used to measure the delivered number of protons up to ultra-high dose rates. The response of transmission ion-chambers, as well as of different field detectors, was characterized over a wide range of dose rates using the Faraday cup as reference. ResultsThe reproducibility of the delivered proton charge was better than 1 % in the proposed experimental setup. EBT3 films, Al2O3:C optically stimulated luminescence detectors and a PTW microDiamond were used to validate the predicted dose. Transmission ionization chambers showed significant volume ion-recombination (>30 % in the tested conditions) which can be parametrized as a function of the maximum proton current density. Over the considered range, EBT3 films, inorganic scintillator-based screens and the PTW microDiamond were demonstrated to be dose rate independent within ±3 %, ±1.8 % and ±1 %, respectively. ConclusionsFaraday cups are versatile dosimetry instruments that can be used for dose estimation, field detector characterization and on-line dose verification for pre-clinical experiments in UHDR proton pencil beams. Among the tested detectors, the commercial PTW microDiamond was found to be a suitable option to measure real time the dosimetric properties of narrow pencil proton beams for dose rates up to 2.2 kGy/s.

Investigation of resistive magnetic field generation by intense proton beams in dense plasmas

Current and future applications of intense proton sources abound, including radiography, cancer therapy, warm dense matter generation, and inertial confinement fusion. With increasingly efficient acceleration and focusing mechanisms, proton current densities may soon approach and exceed 1010 A/cm2, e.g., via intense laser drivers. Simulations have previously shown that in this current density regime, beam-induced field generation plays a significant role in beam transport through dense plasmas. Here, we present a theoretical model for the generation of resistive magnetic fields by intense proton beam transport through solid density plasmas. The theoretical evolution of the magnetic field profile is calculated using an analytic model for aluminum resistivity, heat capacity, and stopping power, applicable from cold matter to hot plasma. The effects of various beam and material parameters on the field are investigated and explained for both monoenergetic and Maxwellian proton beams. For a proton beam with Maxwellian temperature 5 MeV and total energy 10 J, the model calculates resistive magnetic fields up to 150 T in aluminum. The calculated field profiles from several beam cases are compared with 2D hybrid particle-in-cell simulations, with good agreement found in magnitude and time scale.

Sandwich assembly of sulfonated poly (ether sulfone) with sulfonated multiwalled carbon nanotubes as an efficient architecture for enhanced electrolyte performance in H 2 / O 2 fuel cells

Proton exchange membrane (PEM) for H2/O2 fuel cell are made as sandwich assembly of sulfonated poly(ether sulfone) (SPES) with sulfonic acid functionalized multiwalled carbon nanotubes (SMWCNT). The SMWCNT occupies at the middle layer enhances the interfacial interplay and interconnects the nano-phase separation via hydrogen bond between the sulfonic acid of SPES and SMWCNT. The sandwich structure improves the integration of hydrophilic and hydrophobic layers of SPES and SMWCNT, that obliviously enhance the tensile and mechanical property of the membrane. Thus promotes the continuous proton conducting channels through the sandwiched morphology by using the proton hopping mechanism. The 1.5 wt% of SMWCNT in SPES (G3) offers high proton conductivity, current and power density values at 80°C under 100% RH, which are 72.0 × 10−3 S cm−1, 778.26 mA cm−2 and 173.29 mW cm−2, respectively. Within addition to remarkable durability, the OCV degradation is about 0.02 V after 15 hours of durability test and H2 permeability of 2.14 barrer. The excellent thermal stability of 91.2 wt% at 150°C and the Young's modulus of 2208 ± 110 MPa was attained by the G3, which strongly suggest that the promising nature of PEM.

Numerical Analysis of the Local Current Efficiency Distribution in a Protonic Ceramic Fuel Cell Considering Gas Concentration Distributions

Protonic ceramic fuel cells (PCFCs) are expected as highly efficient energy conversion devices due to the high proton conductivity at relatively lower operating temperature (400 ºC~600 ºC) compared to solid oxide fuel cells (SOFCs). The water steam is generated at air side so that there is less fuel dilution at fuel side. Therefore, PCFCs could operate with higher fuel utilization. However, besides the main proton conductivity, some other chargers including electron holes, oxygen ions, and electrons can also be conductive in PCFCs leading a performance decrement. Especially, the electron hole conductivity cannot be neglected inducing a decrease of current efficiency under some operating conditions. The conductivities in PCFCs are not only affected by the operating temperature, but the gas concentrations also strongly influence their values [1]. The conductivities of proton and hole are respectively show positive relationship to steam and oxygen concentrations [2-3]. These properties of PCFCs cause complex for investigating the performances.In this study, the defect transports in a PCFC electrolyte with BaZr0.8Yb0.2O3-δ (BZYb20) material were numerical solved with a quasi-two-dimensional Nernst-Planck-Poisson (NPP) model and the effect of gas concentration on the cell performance was discussed. For the NPP model calculation algorithm, the Nernst-Planck equation (or flux continuity equation) and the Poisson equation are successively solved by finite difference method (FDM) until convergence criteria are obtained with the defect concentration boundary conditions. The defect concentrations at electrolyte membrane surfaces (boundary conditions of NPP model) are derived by equilibrium assumptions of the reactions such as hydration and oxidation reactions. The charge neutrality condition is also added to the boundary conditions for the exact solutions [4]. Subsequently, the local defects (i.e., proton and electron hole) concentrations are revealed, so that the local current efficiency distribution in the PCFC can be revealed.The utilizations of fuel and oxygen are set at 80% and 30%, respectively. The vapor concentration at anode and cathode side are assumed as 3%. The electrolyte thickness is 8 μm in the present study. A constant temperature distribution is assumed in the numerical model. An example result under co-flow gas supply including proton current density and current efficiency distributions is shown in the following figure. The proton current density along fuel flow direction is found to increase from inlet to outlet. The reason can be considered as the influences of water steam distributions. The water steam concentration (or partial pressure) at both fuel and air side increase from inlet to outlet. The current efficiency at downstream are higher than that of upstream. This is contributed by the increase of oxygen in gas flow direction. Moreover, the influences of gas flow direction on cell performances have also been investigated. Acknowledgements This research is primarily based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) Grand Number JPNP20003, Japan. We also extend out special thanks to members of AIST Solid State Ionics Materials Group for useful information and discussions. References Li, et al ., Int. J. Hydrogen Energy, 45 (2020), 34139-149.Okuyama, et al ., Int. J. Hydrogen Energy, 39 (2014), 20829-36.Somekawa T, et al ., Int. J. Hydrogen Energy, 41 (2016), 17539-47.Vøllestad E, et al ., Int. J. Electrochem Soc, 161 (2014), F114-24. Figure 1

Interaction of Liquid Lead Bismuth and Materials in Spallation Target

Material choices for liquid lead bismuth spallation target are some of austenitic stainless steel, ferrite martensitic steel and cold-worked austenitic stainless steel. In order to ensure materials resistance to irradiation and corrosion as well as compatibility with lead bismuth, it is appropriate to lower the incident proton current density and the process temperature, in which temperature range engineering design can control to work, especially in ADS (Accelerator-Driven nuclear transmutation System) concept. The lower limit temperature is determined from the physical melting temperature and the engineering efficiency of the steam generator involved in process control. The material related issues for liquid lead bismuth are mass loss by impinging secondary flow, wettability at the device interface for ultrasonic waves application, detachable control of the slag in the flowing system, stabilized electrical resistance between the material and the liquid lead bismuth interface. Electromagnetic fluid analyses show how flow rate relates electrical resistivity of flow channel material.

Comparative Investigation of Electronic Leakage in Proton-Conducting Ceramics for High-Temperature Water Electrolysis

The electronic conduction within proton-conducting ceramics represents a significant problem for the efficiency of hydrogen production through water electrolysis at high or intermediate temperatures. The doped barium-cerium-zirconate oxides, which have been successfully used for fuel cell applications, however, show electronic leakage when used in water electrolysis that ultimately lowers the Faradaic efficiency of hydrogen production. In this work, the defect chemistry of proton-conducting ceramics was used to evaluate the proton, hole, and electron conductivity from the total conductivity of BaCe0.7Zr0.1Y0.1Yb0.1O3-δ, BaCe0.4Zr0.4Y0.1Yb0.1O3-δ and BaZr0.8Y0.2O3-δ ceramics studied under different steam and oxygen partial pressures. The intrinsic electronic leakage was then related to the Ohmic potential, steam and oxygen partial pressures and temperature. The proton and electronic current densities were calculated from transport equations and then used to estimate the electronic leakage at the specified electrolysis conditions. The comparison of these three materials revealed that the rational material design and optimization of operating conditions can mitigate electronic leakage in electrolytes, which promotes the fast and efficient hydrogen production by proton-conducting solid oxide electrolysis cells.

Cross-Linked SPEEK–PEG–APTEOS-Modified CaTiO3 Perovskites for Efficient Acid–Base Cation-Exchange Membrane Fuel Cell

Nanocomposite membranes are synthesized by the combination of sulfonated poly(ether ether ketone) (SPEEK), poly(ethylene glycol) (PEG), and 3-aminopropyl triethoxysilane (APTEOS)-modified CaTiO3. From thermogravimetric analysis (TGA) and mechanical and Arrhenius studies, it is seen that the covalent cross-linking of PEG with SPEEK exhibits a lower weight loss (91.84 wt %) at 120 °C than SPEEK (88.19 wt %). Moreover, higher activation energy (Ea) and tensile stress values are obtained in the order of 26.23 kJ/mol and 23.32 MPa, respectively. The APTEOS-modified CaTiO3 nanoparticles impregnated into the SPEEK/PEG membrane cause the acid–base proton hopping mechanism (HSO3/NH2) and induce a more compact structure. The nanocomposite membranes possess exceptional proton conductivity, thermal, oxidative, and physicochemical properties than SPEEK. Further, 6 wt % functionalized CaTiO3 in the SPEEK/PEG membrane manifests the highest values of proton conductivity, current density, and power density at 80 °C in 100% RH of 65.32 mS cm–1, 403 mA cm–2, and 90 mW cm–2 with an open-circuit voltage (OCV) of 0.90 V, respectively. This membrane retains 95.37 wt % original weight during 3 h of the Fenton test.

Molecular Basis of Voltage-Gated Proton Channel's Intracellular Trafficking

Voltage-gated proton channel (HV1) presents a physiological role of great importance to phagocytosis and sub sequential death of microorganisms in phagocytic cells, such as neutrophils and microglia. Recently various studies describe the contribution of this channel in a higher malignity of tumors and its proliferation. Additionally, HV1 channels have been related to augmented tissue damage in cerebral stroke. Even though these pathological processes have been associated with a higher superficial expression of HV1 channels, little is known about how their abundance in the plasma membrane is regulated. Thus, by combining molecular approaches, in this work we have studied the molecular mechanisms of HV1 channel's intracellular trafficking, associating modifications in its C-terminal domain with its intracellular localization. Therefore, full length human voltage-gated proton channel (hHV1 WT) was fused with the fluorescent protein mCherry and site-directed mutagenesis were made in order to delete the C-terminal domain completely (V220X) or partially (I242X and I256X). Electrophysiological recordings of CHO-K1 cells transfected with hHV1 WT and the C-terminal truncated mutants showed that only the V220X mutant significantly reduced the proton current density. Thus, suggesting that the surface expression of this mutant is compromised. High-resolution microscopy analysis of hHV1 WT intracellular localization through co-transfection with 8 different intracellular organelles markers fused with EGFP resulted in a marked co-localization with Rab11, which is present in recycling endossomes. Furthermore, acute treatment of hHV1 WT transfected CHO-K1 cells with microtubule and actin disruptive agents, nocodazole and cytochalasin D respectively, diminished the proton current density significantly. Overall these results indicate an association of hHV1 WT with recycling endosomes, a key role of both cytoskeletal components and of the C-terminal domain in hHV1 forward trafficking.

The Influence of Proton Irradiation on Properties of Glass with ITO Coating

Changes in the surface morphology and optical properties of the samples of K208 glass with an ITO film are studied after the effect of protons with an energy of 20 keV and a dose of 0.2–1.0 mC/cm2 at a proton current density of 9 nA/cm2. It is shown experimentally that the presence of the ITO film affects the character of morphology changing and is the main reason for the degradation of the sample optical properties at the proton irradiation.

Advanced nanocomposite membranes based on sulfonated polyethersulfone: influence of nanoparticles on PEMFC performance

Two types of innovative new nanocomposite membranes based on sulfonated polyether sulfone (SPES) containing LaCrO3 and TiO2 nanoparticles were prepared in the present study and studied for their possible employment in proton exchange membrane (PEM) fuel cells. The nanocomposite membranes demonstrated high thermal and mechanical stability compared with pure SPES membrane due to the presence of TiO2 and LaCrO3 nanoparticles. The SPES–LaCrO3 nanocomposite membranes displayed high proton conductivity and fuel cell performance compared to SPES–TiO2 nanocomposite membranes due to fast proton transfer of LaCrO3 nanoparticles, which acted as water trap due to rotational motion of the proton in their perovskites structure. The proton conductivity and current density (at 0.5 V) at 80 °C were obtained 82 mS/cm and 0.92 A/cm2, respectively, for the SPES–LaCrO3 nanocomposite membranes containing 1 wt% of LaCrO3 nanoparticles. According to the obtained results from this study, the SPES–LaCrO3 nanocomposite membranes are promising membranes for PEM fuel cells.

Влияние протонного облучения на свойства стекла с покрытием ITO

Changes in the surface morphology and optical properties of K208 glass samples with an ITO film as a result of exposure to 20-keV protons at a dose of 0.2–1.0 mC/cm2 and a proton current density of 9 nA/cm2 were studied. It has been experimentally shown that the presence of an ITO film affects the nature of the change in morphology and is the main cause of the degradation of the optical properties of samples during proton irradiation.

Proton Transfer Can Occur at High Rates through Single-Layer Graphene in Nafion | Graphene | Nafion Sandwich Structures

Hydrogen pump cells fabricated from Nafion membranes and Pt-on-carbon electrodes were used to measure rates of proton transfer across single-layer graphene embedded in Nafion | graphene | Nafion sandwich structures. Single-layer graphene prepared by chemical vapor deposition onto copper foil was sandwiched between Nafion membranes by a series of hot-pressing steps coupled with chemical etching to remove the copper. Proton current densities in excess of 1 A / cm2 were observed for proton transfer across the graphene at cell bias voltages less than 200 mV. Confocal Raman spectroscopy measurements of the Nafion / graphene sandwich structures are consistent with single-layer graphene having very few structural defects embedded between Nafion membranes. Ion-transfer rates for lithium, sodium, potassium, and other cations were also measured and found to be much lower than rates for proton transfer, in most cases by many orders of magnitude. Two-layer and few-layer (3-5 layer) graphene sandwich structures were also studied and found to give proton currents much lower than single-layer graphene. Proton currents are described in terms of an area-normalized resistance following correction for all other contributions to series resistance in the cells. Resistances are then analyzed in terms of a rate constant for proton self-exchange across graphene. Figure 1

Proton acceleration in two-species targets irradiated by an ultra-intense femtosecond laser pulse

This paper presents results of two-dimensional particle-in-cell simulations of proton acceleration at the interactions of a 130 fs, linearly polarized laser pulse of intensity from the range 1021 –1023 W/cm2, predicted for the ELI (Extreme Light Infrastructure) lasers, with thin hydrocarbon (CH) or hydride (ErH3) targets. It is shown that for the targets of the areal density σ > 0.1 mg/cm2 and laser intensities below 1022 W/cm2 a higher efficiency of proton acceleration is achieved for hydride targets. However for the highest, ultra-relativistic laser intensities (~ 1023 W/cm2) considerably higher proton energies and proton beam intensities are achieved for thin (σ ≤ 0.1 mg/cm2) CH targets. In this case, at short distances from the irradiated CH target (< 50 um), the generated proton pulses are very short (< 20 fs), and the proton beam intensities and the proton current densities reach extremely high values, > 1021 W/cm2 and > 1012 A/cm2, respectively, which are much higher than those attainable in conventional accelerators. Such proton beams can open the door for new areas of research in nuclear physics and high energy-density physics as well as can be useful for materials research.

Approximate analytical solution to MHM equations for PEM fuel cell cathode performance

We report approximate analytical solutions for the shapes of the overpotential, oxygen concentration and proton current density through the depth of a PEM fuel cell cathode and for the cathode polarization curve. The solution is obtained by applying a homotopy analysis method to the standard macrohomogeneous equations for the electrode performance. For typical cell parameters, the solutions are valid up to the cell current density on the order of ≃ 500mAcm−2.

Synthesis and characterization of hybrid composite membranes and their properties: Single cell performances based on carbon black catalyst/proton-conducting hybrid composite membrane for H2/O2 fuel cells

In this study, a class of less expensive non-platinum catalyst (carbon black catalyst) and proton-conducting hybrid composite membranes based on polyvinylpyrrolidone (PVP) were introduced. Properties and performances of the new materials as proton exchange membrane for use in fuel cells operating at low temperatures were investigated to reduce the costs. A maximum conductivity value of 0.4Scm−1 was obtained at 100°C with excellent thermal and mechanical stability of the membranes. This is the first time such a high proton conductivity value has been achieved for SiWA/MPTMS/SiO2/GA/PVP hybrid composite membrane. A maximum current density of ~700mAcm−2 for the membrane-electrode-assemble (MEA), consisting of Carbon black based catalyst and hybrid composite membrane was obtained at 80°C and 100% relative humidity. To the best of my knowledge, no reports have been published using the same non-Pt catalyst with hybrid composite membrane electrolyte providing high current density at low temperatures. In this paper, two systems that present high proton conductivity and current density at relatively low temperatures by the combination of hybrid composite membrane and non-platinum catalyst (Carbon black catalyst).

A GLOBAL MAGNETIC TOPOLOGY MODEL FOR MAGNETIC CLOUDS. IV.

ABSTRACT In the first paper of this series, we introduced a global topology model for the study of magnetic clouds (MCs), fitting it to the experimental magnetic field components and obtaining, for example, the orientation of the axis of the MCs in the interplanetary medium. In the third paper, we extended the model to include theoretical hydrostatic plasma pressure, also incorporating it in the fitting procedure. The present work is complementary to the previous ones, now incorporating the proton current density as deduced from the continuity equation. In particular, we are interested in the component of the proton current density parallel to the magnetic field lines of the MC, , because the perpendicular component is expected to have information similar to the plasma pressure. Under all of these conditions, our fitting procedure now involves simultaneous analysis of the three components of the magnetic field, the trace of the plasma pressure, and the parallel proton current density. This provides us with more information about the physical mechanisms taking place inside MCs, thus helping us to understand the propagation and evolution of these structures in the interplanetary medium.

Properties of Hermean plasma belt: Numerical simulations and comparison with MESSENGER data

AbstractUsing a global hybrid model and test particle simulations we present a detailed analysis of the Hermean plasma belt structure. We investigate characteristic properties of quasi‐trapped particle population characteristics and its behavior under different orientations of the interplanetary magnetic field. The plasma belt region is constantly supplied with solar wind protons via magnetospheric flanks and tail current sheet region. Protons inside the plasma belt region are quasi‐trapped in the magnetic field of Mercury and perform westward drift along the planet. This region is well separated by a magnetic shell and has higher average temperatures and lower bulk proton current densities than the surrounding area. On the dayside the population exhibits loss cone distribution function matching the theoretical loss cone angle. The simulation results are in good agreement with in situ observations of MESSENGER's (MErcury Surface Space ENvironment GEochemistry, and Ranging) MAG and FIPS instruments.