Optimization of Transfer Processes in a Solid Polymer Electrolyte Fuel Cell

Abstract

ev, Kalinnikov, Porembskii, Sister, Fateev, Rusanov. Recently, in the context of solving environmental and energy problems, interest in widely using solid polymer electrolyte fuel cells for both transportation and stationary applications has significantly increased. Although there are a lot of developments in fuel cells of this type, it is necessary to perform integrated optimization of the bipolar plate-gas-diffusion layer-electrocatalytic layer-membrane system taking into account the parameters of each of the components. For example, a significant problem is to optimize the sizes of channels and projecting current-carrying elements of the bipolar plate, as well as the thickness and porosity of the gasdiffusion layer. Previously [1, 2], we developed a twodimensional diffusion model of mass transfer in a solid polymer electrolyte fuel cell. Within this model, it was shown that, at operating current densities, diffusion limitations may arise in the gas-diffusion layer. In this work, we continue to study this problem for gas-diffusion layers of different composition and structure with allowance for the ohmic loss and the sizes of the channels and projecting current-carrying elements of the bipolar plate. Figure 1 presents all characteristic regions of a solid polymer electrolyte fuel cell. These regions, numbered 1 -8 , are considered in the model separately and are coupled to each other by boundary conditions. The model comprises the following processes: the transport of the reactant and water in the channels of the bipolar plate, the gas-diffusion layer, the electrocatalytic layer, and the membrane; the proton current in the membrane and the electrocatalytic layer; the electron current in the electrocatalytic layer, the gas-diffusion layer, and the projecting current-carrying elements of the bipolar plate; and the heat transfer in all the components indicated. MATHEMATICAL MODELThe model is formulated under the following basic assumptions: the gas in the channels of the bipolar plate is ideal and flows at a constant pressure; the longitudinal component (along the z axis) of the gas velocity in the gas-diffusion layer is zero; the total pressure in the cathodic and anodic zones is the same; all the mass transfer processes occur at constant pressure; the catalytic layer thickness is negligible; and the contacting surfaces of the bipolar plate and the gas-diffusion layer have equal temperatures and are equipotential.The mass transfer in the channels of the bipolar plate and the gas-diffusion layer was described by the Stefan-Maxwell equation. The gas flow distribution in the channels was characterized by the Navier-Stokes equation for a quasi-stationary flow. The proton current in the membrane and the electrocatalytic layer was calculated by the Nernst-Planck equation. The thermal processes were described by the corresponding heat transfer equations.According to the problem under consideration in this work, let us dwell in greater detail on the transport of the reactant and electrons in the gas-diffusion layer. ...

Effects of operating parameters on the performance of a high-pressure proton exchange membrane electrolyzer

“…High-purity hydrogen generation is possible with PEM electrolyzers up to 99.999% [6]. PEM electrolyzers can operate at higher current ranges and thus allow compact structures compared with other hydrogen production methods [7]. The high-pressure hydrogen production provides direct storage to the high-pressure tanks, eliminating the noisy and the energy consuming mechanical hydrogen compressors.…”