Theoretical performance of a hydrogen-bromine rechargeable SPE fuel cell

doi:10.1016/0378-7753(88)80035-1

Journal of Power Sources

Volume 22, Issues 3–4, March–April 1988, Pages 423-440

https://doi.org/10.1016/0378-7753(88)80035-1 Get rights and content

Abstract

A mathematical model was formulated to describe the performance of a hydrogen-bromine fuel cell. Porous electrode theory was applied to the carbon felt

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Cited by (43)

Mass transport limitations in concentrated aqueous electrolyte solutions: Theoretical and experimental study of the hydrogen–bromine flow battery electrolyte
2023, Electrochimica Acta
Modelling and simulation is a powerful tool to support the development of novel flow cells such as electrolysers and flow batteries. Electrolytes employed in such cells often consist of aqueous solutions of highly concentrated solutes at elevated temperatures. Such conditions pose numerous challenges in conventional model parametrisation because of non-ideal behaviour of the electrolytes. The aim of this work is to study mass transport of electroactive species in highly-concentrated media.
We selected the hydrogen–bromine flow battery posolyte, HBr (aq) and Br₂, as an exemplary flow battery electrolyte and we leveraged chronoamperometric techniques involving ultramicroelectrodes to study diffusion and migration of bromide and bromine at high concentration and temperature. We successfully simulated the current densities of HBr/Br₂ redox reactions in solutions up to 8 mol L^–1 using advanced mass transport theory which agreed well with the results obtained with ultramicroelectrodes.
While uncharged species transport (Br₂) can be credibly modelled using conventional theories such as Fick’s law, charged species (Br^–) require special treatment as the diffusion coefficient vary with concentration up to 50 % with respect to the limiting value at infinite dilution. The transport of charged species without added supporting electrolyte occurs via both migration and diffusion and the contribution of migration current may be up to 50 % of the total current. At HBr concentration $>$ 0.6 mol L^–1 migration appears to be suppressed due to the “self-screening” effect of the electrolyte.
Proper experimental electrolyte characterisation under operating conditions similar to the actual flow cell applications is indispensable to establish predictive models and digital twins of electrochemical devices. Straightforward transfer of concepts known in electro-analytical chemistry to flow cells modelling may lead to erroneous simulations or model overfitting.
Exploring the thermodynamics of the bromine electrode in concentrated solutions for improved parametrisation of hydrogen–bromine flow battery models
2021, Journal of Power Sources
Thermodynamic properties of the bromine electrode in an exemplary hydrogen–bromine flow battery (HBFB) are investigated in detail. Open-circuit potential (OCP) measurements of HBRB electrolytes in a liquid junction-free setup and electrolyte Raman spectra are employed to estimate polybromides speciation. An improved mathematical description of the bromine electrode OCP versus state of charge is provided.
This paper addresses the phenomenon of polybromides formation at concentrations up to 7.7 mol L^-1 HBr and 3.85 mol L^-1 Br₂ and their significant impact on the OCP. The model takes into account tri-, penta- and heptabromides formation, precisely modelled electrolyte activity coefficients (up to 11-molal HBr), electrolyte density, and temperature. It is elucidated that the polybromide formation constants found in literature treating dilute electrolytes are substantially too low. Newly determined equilibrium constants, applicable over a wider concentration range are provided for 25 and 43 °C together with their standard enthalpy changes. The model is successfully validated in an independent experiment using a real, pilot-scale HBFB.
It is concluded that the usage of a simple Nernst-like equation to calculate the OCP of flow battery electrodes containing concentrated electrolytes leads to erroneous results.
Study of bromine species crossover in H<inf>2</inf>/Br<inf>2</inf> redox flow batteries
2017, International Journal of Hydrogen Energy
Citation Excerpt :
As compared to the experimental works, relatively few modeling and simulation works of H2/Br2 RFBs can be found in the literature [10–12]. Savinell and Fritts [10] developed a one-dimensional (1-D) H2/Br2 RFB model along the cell thickness direction, accounting for the electrochemical reactions of H2/Br2 and the resultant proton and bromide transport through porous components. Later, they conducted detailed analysis of hydrogen electrode properties such as platinum (Pt) particle size, Pt loading, and porosity.
A three-dimensional (3-D) model for H₂/Br₂ redox flow batteries (RFBs) is developed by rigorously accounting for the redox reactions of hydrogen and bromine species, and the resulting species and charge transport through various cell components. First, the H₂/Br₂ RFB model is experimentally validated against the discharge and charge voltage curves measured over a wide range of current densities up to 1.4 A cm⁻². In general, the model predictions compare well with the experimental data, and they further reveal key electrochemical and transport phenomena inside the cell. Particular emphasis is placed on analyzing the crossover of bromine species through the membrane at detailed levels where the model calculates electro-osmotic and diffusive fluxes of bromine species across the membrane; the relative magnitudes are compared under various charging and discharging stages. In addition, a parametric study is carried out to examine the effects of two key design variables on cell performance and crossover behavior, i.e., the thicknesses of the membrane and bromine porous media. This full 3-D H₂/Br₂ RFB model can be applied to realistic large-scale cell geometry for grid-scale energy storage applications and directly utilized to determine the optimal design and operating conditions for H₂/Br₂ RFBs.
Nafion/PVDF nanofiber composite membranes for regenerative hydrogen/bromine fuel cells
2015, Journal of Membrane Science
Nanofiber composite proton exchange membranes were fabricated and their properties measured, for possible use in a regenerative hydrogen/bromine fuel cell. The membranes were prepared from dual nanofiber mats, composed of Nafion^® perfluorosulfonic acid (PFSA) ionomer for proton transport and polyvinylidene fluoride (PVDF) for mechanical reinforcement. Two composite membranes structures containing Nafion volume fractions ranging from 0.30 to 0.65 were investigated: (1) Nafion nanofibers embedded in a PVDF matrix (N(fibers)/PVDF) and (2) PVDF nanofibers embedded in a Nafion matrix (N/PVDF(fibers)). The in-plane conductivity for films equilibrated in water and 2.0 M HBr scaled linearly with Nafion volume fraction for both morphologies. The through-plane proton conductivity of N(fibers)/PVDF membranes in water was lower than that of N/PVDF(fibers) films with the same Nafion content for films with less than 55 vol% Nafion, e.g., 0.03 S/cm for N(fibers)/PVDF membrane vs. 0.04 S/cm for N/PVDF(fibers) membrane at 40 vol% Nafion. N(fibers)/PVDF membranes exhibited excellent Br₂/ ${Br}_{3}^{-}$ barrier properties with a reasonable membrane resistance, e.g., a N(fibers)/PVDF membrane with 40 vol% Nafion and a thickness of 48 µm had the same area-specific-resistance as Nafion^® 115 (0.13 Ω cm²) but its steady-state Br₂/ ${Br}_{3}^{-}$ crossover flux was 3.0 times lower than that of Nafion 115 (1.43×10⁻⁹ mol/s/cm² vs. 4.28×10⁻⁹ mol/s/cm²).
The characterization of graphite felt electrode with surface modification for H<inf>2</inf>/Br<inf>2</inf> fuel cell
2013, Journal of Power Sources
Citation Excerpt :
Therefore, large-scale electrical energy storage systems are required to cope with the variable generation of electricity. H2/Br2 fuel cell is being considered for affordable grid-scale and intermittent renewable electricity storage due to the high electric-to-electric efficiency (>90% at 108 mA cm−2) because of fast electrochemical reaction kinetics of both the hydrogen and bromine electrodes [3–6]. The H2/Br2 fuel cell consists of a bromine electrode and a hydrogen electrode with a proton-conducting membrane between them.
Graphite felt is used as the bromine electrode in H₂/Br₂ fuel cell, which is surface modified by acidic oxidation and thermal oxidation for improving cell performance. The structure, composition, electrochemical properties and performances of the modified electrodes are characterized with X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electrochemistry impedance spectroscopy and single cell polarization curves. The maximum power densities are improved from the original 0.51 to 0.62 and 0.69 W cm⁻² after acidic oxidized at 80 °C for 8 h and thermal oxidized at 500 °C for 5 h, respectively. The performance improvement may be attributed to the increase in oxygen-containing functional groups and surface area which could increase the electrochemical catalytic activity and thus decrease the charge transfer resistance. However, the ohmic resistance and charge transfer resistance increase after superabundant oxidation, which causes badly deteriorates in cell performance.
IrO<inf>2</inf> coated TiO<inf>2</inf> nanopore arrays electrode for SPE HBr electrolysis
2013, Journal of Electroanalytical Chemistry
IrO₂ nanoparticles coated TiO₂ nanopore arrays (IrO₂/TNPs) electrode has been successfully synthesized by depositing IrO₂ on the surface of size-controllable TiO₂ nanopore arrays (TNPs), which were fabricated by using anodic oxidation of pure titanium meshes in electrolyte solutions. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), liner sweep voltammetry (LSV), SPE cell polarization curves and electrochemistry impedance spectroscopy (EIS) were adopted to characterize their structures, properties and performances. The IrO₂/TNPs electrode has ordered microstructure and more porous surface morphology than that of IrO₂/Ti electrode. The electrochemical tests showed that IrO₂/TNPs electrode exhibited higher catalytic activity than IrO₂/Ti electrode. And the cell voltage can be as low as 1.16 V at 1000 mA cm⁻² and 70 °C, which is 90 mV lower than that of the cell with IrO₂/Ti electrode (1.25 V). The increase in performance is attributed to the ordered microstructure and porous surface which decrease the interface contact resistance and charge transfer resistance.

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