A physicochemical model of a water electrolyzer with a polymer electrolyte membrane (PEM) was developed, taking into account the electrochemical dissolution of an anodic iridium catalyst. The dependencies of the rates of iridium loss and electrolysis voltage increase upon the current density were calculated in order to analyze the effect of the iridium dissolution on degradation of the electrolysis cell (EC) performance. As an estimated characteristic of the techno-economic costs of the electrolysis process, the amount of iridium loss from the anode catalyst layer (as a result of electrochemical dissolution) in the course of the generation of 1 kg of hydrogen was calculated. Data were analyzed and a number of regularities of the iridium dissolution and its influence on the rate of degradation of the EC performance were found. In particular, the most efficient ECs in terms of electrolysis voltage (energy consumption for gas production) are, simultaneously, the most unstable (prone to performance degradation) in relation to the iridium dissolution process. An aim of current requirements for water electrolyzers includes reducing the specific consumption of iridium required for hydrogen generation. & COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Various regimes of gas-liquid flows in porous transport layers/current collectors and their effect on the performance of a model electrolysis cell based on a polymer electrolyte membrane (PEM) are described, based on mathematical simulation. The latter is based on the utilization of a standard description of the two-phase transfer of liquid water, water vapor, and noncondensable gasses in porous media. Numerical calculation with usage of model developed for porous transport layers of an electrolysis cell allowed the determination of the optimal operational parameters for the basic components of the electrolysis cell in dependence of their parameters. Operating conditions causing critical modes of mass transport were identified as well. This study reports of the results of a numerical analysis and discuss consequences for the components of the PEM-based electrolysis cell selection and on its electrical characteristics. (c) 2021 Elsevier Ltd. All rights reserved.

In this paper, we implement the most rigorous approach to the mathematical description of two-phase transfer processes in liquid water, water vapor, and non-condensable gases (hydrogen and oxygen) in gas-diffusion electrodes/current collectors of water electrolyzers based on a polymer electrolyte membrane. The solution to this problem allowed the following to be determined: various movement modes of gas–liquid flows and their effects on electrolyzer performance; optimal parameters of gas-diffusion electrodes (thickness, porosity, permeability, wetting angle), depending on the required operating mode of the electrolyzer (current density, temperature, pressure); and possible reasons for the incorrect operation of the electrolyzer.

The paper deals with the nonequilibrium poroelectroelastic theory (PEET) for polymer electrolytes (PE) under the conditions of water electrolysis with a view of further use in the theoretical description of mass transfer processes in layers of a membrane–electrode assembly. Moreover, this paper presents a review and analysis of the models of electrochemical and mass-transfer processes in electrolyzers, and analyzes problems associated with their physicochemical description. The authors came to the conclusion that it was necessary to use models of water sorption and PE swelling. It was further concluded that the existing PEET may be most suitable to be modified for use under nonequilibrium conditions during electrolysis. The fundamental equation for pressure balance of the classical equilibrium PEET for PE was considered. A modification of the PEET was carried out in order to use it under nonequilibrium conditions of water electrolysis for the purpose of further modeling of mass transfer processes. Based on experimental data available in open sources, the authors studied properties and features of the elastic forces in PEs, and then refined the dependencies of the elastic forces in PE on swelling and temperature. Taking into account the existing experimental data on the permeability of gases in a PE and the swelling property of a PE when in a contact with liquid water, parameters of the nonequilibrium PEET were obtained for the conditions of water electrolysis.

The comparative study of electrocatalysts synthesized by chemical reduction and pulsed magnetron-ion sputtering for polymer electrolyte membrane electrochemical systems are presented.Various carbon nanomaterials were used as supports of Pt nanoparticles: carbon black, nanotubes, nanofibers and reduced graphene oxide.The electrochemical studies of the obtained electrocatalysts as well as their testing in the fuel cell membrane-electrode assembly were carried out.The influence of supports morphology and the deposition approach of Pt nanoparticles on the electrochemically active surface area and activity of electrocatalysts, as well as the prospects of the magnetron-ion sputtering approach for electrocatalysts synthesis were studied and discussed.

The Monte Carlo simulation method is used to carry out numerical modelling of the polymer electrolyte membrane fuel cell (PEMFC) catalyst layer with a random catalyst particles distribution in a polymer matrix. The approaches of mass transport and electrochemical kinetics are applied for estimation of potential distribution and current generation in the catalyst layer. It is shown that large particles of the catalyst support (agglomerates of nanofibers) provide percolation for electron transport at a lower concentration in comparison with compact catalyst support particles (i.e. Vulcan XC-72R). Mixtures of such supports also have a lower percolation threshold. It gives the possibility to increase polymer concentration, stabilise water balance and decrease ohmic losses for ion transport in the catalyst layer. The numerical estimations demonstrate the possibility of precious metal loading reduction up to 30% and the increase of performance (current density) up to 20% just due to addition of carbon nanofibers in the catalyst layers. In the experimental study we reached an increase of PEMFC current density for about 10% when we used the Vulcan XC-72R supported Pt catalyst together with the Pt catalysts on nanofibres

The paper considers a non-equilibrium poroelectroelastic theory of a polymer electrolyte under the conditions of water electrolysis with the purpose of further use for a theoretical description of mass transfer processes in l ayers of a membrane-electrode assembly. Moreover, this paper carries out the review and analysis of the models of electro- chemical and mass-exchange processes in the electrolyzers, and analyzes the problems of their physicochemical description. We make a conclusion about the need to use models of water sorption and scaling of polymer electrolyte and analyze the models of water sorption and swelling of the polymer electrolyte. It is concluded that the existing poroelectroelastic theory is the most suitable for its modification for use in non-equilibrium conditions during elec- trolysis. The basic equation of the balance of pressures of the classical equilibrium poroelectroelastic theory for polymer electrolyte is considered. A modification of the poroelectroelastic theory has been carried out in order to its use in non-equilibrium conditions of water electrolysis for the purpose of further modeling of mass transfer processes. Based on experimental data available in open sources, the paper makes an analysis of the properties and features of elastic forces in the polymer electrolyte, and then refines the dependencies of the elastic forces in the polymer electro- lyte from the swelling and temperature. Taking into account the existing experimental data on the permeability of gases in a polymer electrolyte and the feature of swelling of the polymer electrolyte in a contact with liquid water, parameters of the non-equilibrium poroelectroelastic theory have been obtained for the water electrolysis conditions.

Electrochemical process of atmospheric oxygen concentration in a modified electrolytic cell with a solid polymeric electrolyte and cathode depolarized by atmospheric oxygen was experimentally studied. The influence exerted by various factors (catalyst hydrophobicity, temperature, pressure, and air supply rate) on the process efficiency was examined. It was shown that the energy consumption for obtaining high-purity oxygen in this process can be reduced by 50–75% as compared with obtaining oxygen by electrolysis of water. The highest activity was observed for Pt40V catalyst (40 wt % Pt on Vulcan XC-72 carbon black) containing 10 wt % fluoroplastic.

This paper describes a numerical and experimental analysis of the optimum loadings of noble metals (Pt, Ir) in electrocatalytic layers of the polymer electrolyte membrane (PEM) water electrolysis cells. Based on the obtained results, the Pt loading of ca. 0.4 mg/cm(2) (or 1 mg/cm(2) of Pt/C with 40 wt. % of Pt) and ca. 2.5 mg/cm(2) of IrO2 loading could be recommended. The developed mathematical model has shown that these optimum values are derived from the interference of activation and ohmic losses in the electrocatalytic layers. The membrane-electrode assembly (MEA) with these noble metal contents does not exhibit significant catalytic layer degradation within 4000 h of operation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This paper is devoted to the numerical optimization of the geometry of some key cell components (flow-field channels, current transfer ribs of bipolar plates, gas diffusion electrodes) of high-temperature PEM fuel cells using H3PO4-doped Poly Benzimidazole (PBI) as solid polymer electrolyte. Some design specifications as well as optimum values of key operating parameters are proposed to increase the efficiency of such fuel cells. For this purpose physicochemical model and corresponding novel effective technique for solving of 2D transport equation have been developed. Results of the numerical analysis of dependence of fuel cell performances upon the geometry of cathodic and anodic flow-field channels, operating temperature and gas diffusion electrode parameters are provided. In particular, it was demonstrated that optimum relative width of current-transfer rib (i.e. the ratio between width of rib divided to sum of widths of rib and channel) is determined mainly by competition between diffusion and current conductivity in a gas diffusion electrode and is approximately equal to 0.30–0.35 for the parameters of cell components used in this study.

Composition and structure of proton-exchange membrane (PEM) fuel cell catalytic layers were investigated. The maximum FC efficiency was observed at the polymer content in a layer 25-30 vol.% at work on air and 30-35 vol. % at work on oxygen. At a variation of quantity of catalytic composition the maximum current density have been received at layer load 1.75 mg/sm2, thus decrease in it value in 2 times leads to falling of current density only on 10%.

Electrochemical hydrogen pumps are electrochemical devices which are used for hydrogen purification and pressurization purposes. In such cells, gaseous hydrogen is oxidized at the anode and released at the cathode. Results presented in this paper are related to the characterization and optimization of a proton-exchange membrane (PEM) hydrogen pump using electrochemical impedance spectroscopy (EIS). Only the case of hydrogen purification is considered here. Current–voltage characteristics have been measured. The kinetics and efficiency of the cell have been investigated using EIS. The roles played by the cell structure (in particular by the ion-exchange polymer content in the electro-catalytic layers) and by different operating parameters (the cell temperature, the relative humidity and the partial pressure of hydrogen) on the overall process efficiency have been evaluated and are discussed.

This paper is devoted to the modeling and numerical optimization of proton-exchange membrane (PEM) water electrolysers for operation at elevated pressures (up to 130 bars). The model takes into account different geometrical parameters of the PEM cell, the kinetics of the hydrogen and oxygen evolution reactions, the electro-osmotic drag of water molecules, the permselectivity of the solid polymer electrolyte and associated gas cross-over phenomena. The role of various operating parameters (such as pressure, temperature, current density, flow rate of water) on cell efficiency, faradaic yield and heat produced during water electrolysis is evaluated and discussed. The model is also used for the purpose of optimizing the performances of PEM cells. In particular, optimal values of some critical operating parameters (current density, rate of water supplied to the anodes) are recommended.

This paper is devoted to the numerical optimization of the dimensions of channels and current transfer ribs of bipolar plates as well as the thickness and porosity of gas diffusion layers. A mathematical model of the transfer processes in a PEM fuel cell has been developed for this purpose. The results are compared with experimental data. Recommendations of the values of operating parameters and some design requirements to increase PEM fuel cell efficiency are suggested.

At present time proton exchange membrane fuel cells are being intensively developed for vehicular, portable, stationary and other applications. However some fuel cell components such as gas diffusion layer and bipolar plate need an optimization. Both experimental methods and the mathematical models developed for this purpose by the authors are presented for review in this article.

Математическое моделирование процессов переноса в топливном элементе с твердым полимерным электролитом The physical-chemical model of fuel cell with proton exchange membrane (PEM) is described in the article. Model has shown that there is an optimum for width of channels and prominent current transfer elements of bipolar plate depending on parameters of gas diffusion layer. Experiments have been provided for verification of model, these experiments have qualitatively confirmed results of calculations. On the basis of the developed model, in view of concrete parameters and operation mode of fuel cell, optimum values of bipolar plate and gas diffusion layer parameters were recommended at which efficiency of PEM fuel cell will be maximal.

A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally.