Examinando por Autor "Zenyuk, Iryna V."

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Boosting the performance of polymer electrolyte membrane fuel cells with porous flow fields: Pros and cons
(Elsevier, 2025-03-01) García-Salaberri, Pablo A.; Perego, Andrea; Wu, Rui; Zenyuk, Iryna V.
The design of the cathode flow field plays a relevant role in the performance of proton exchange membrane fuel cells (PEMFC). Recently, porous flow fields have emerged as an alternative to conventional rib/channel flow fields (e.g., serpentine flow field) in an attempt to increase PEMFC performance. In this work, we aim to shed light on pros and cons of both bipolar plate types by analyzing transport through porous and rib/channel flow fields using experimental and numerical work. The experimental polarization curves and oxygen transport resistance data of a cathode porous flow field are used to validate the numerical model. Then, a comprehensive parametric study of the model is presented, involving both operating and constructive parameters. The results show that the main advantages of porous flow fields are: (𝑖) the improvement of oxygen transport, (𝑖𝑖) the decrease of flooding in the cathode MEA, and (𝑖𝑖𝑖) the increase of the distribution homogeneity in the in-plane direction of physical parameters (e.g., current density and temperature). In contrast, the main disadvantages are: (𝑖) the potential effect of electrical contact resistances between porous surfaces, and (𝑖𝑖) the decrease of the water removal drag force in the cathode channel. The above two issues can be mitigated using: (𝑖) thinly manufactured foams and/or increasing the assembly compression, and (𝑖𝑖) hybrid porous flow fields that incorporate a rib/channel pattern with fine pore-size porous ribs.
Examining the mass transport resistance of porous transport layers at the rib/channel scale in polymer electrolyte membrane water electrolyzers: Modeling and design
(Elsevier, 2025-07) García-Salaberri , Pablo A.; Lang, Jack Todd; Chang , Hung-Ming; Firas, Nausir; Shazhad, Hasan; Zenyuk, Iryna V.
The porous transport layer (PTL) plays a relevant role in the efficiency of polymer electrolyte membrane water electrolyzers (PEMWE). Extraction of good design guidelines for this porous component is necessary for efficient water/oxygen transport. In this regard, numerical modeling provides a versatile tool to examine large parameter set and determine optimal PTL conditions to be verified experimentally. Here, a hybrid model is presented to analyze two-phase transport of oxygen and water in the anode PTL of a PEMWE. Oxygen capillary transport is modeled with a multi-cluster invasion-percolation algorithm, while water convective transport is modeled with a continuum formulation that incorporates the blockage of gas saturation. The model is validated against in-operando X-ray computed tomography data of the oxygen saturation distribution at the rib/channel scale. Subsequently, a comprehensive parametric analysis is presented, considering the following variables: (𝑖) PTL slenderness ratio, (𝑖𝑖) flow-field open area fraction, (𝑖𝑖𝑖) PTL isotropy, (𝑖𝑣) PTL average pore radius, and (𝑣) PTL pore-size heterogeneity. Among other conclusions, the results show that the water transport resistance under the rib can lead to non-negligible mass transport losses at high current density. Water transport from the channel to the catalyst layer can be promoted by: (𝑖) the use of PTLs with a slenderness ratio, defined as the PTL thickness to rib half-width ratio, around 0.5, (𝑖𝑖) the increase of the flow-field open area fraction, (𝑖𝑖𝑖) the design of highly anisotropic PTLs with a relatively large pore radius between 𝑟𝑝 ∼ 10 − 40 μm, and (𝑖𝑣) increasing the homogeneity of the PTL microstructure
The critical role of the anode porous transport layer/catalyst layer interface of polymer electrolyte membrane water electrolyzers: A parametric analysis
(Elsevier, 2025-04-01) García-Salaberri, Pablo A.; Chang , Hung-Ming; Lang, Jack Todd; Firas, Nausir; Shazhad , Hasan; Morimoto, Yu; Zenyuk, Iryna V.
Reducing the dependency of proton exchange membrane water electrolyzers (PEMWE) on precious metals, such as iridium (Ir), is necessary to develop a widespread green hydrogen system. This challenge requires a careful design of the interface between the anode porous transport layer (PTL) and the catalyst layer (CL). A comprehensive numerical analysis of relevant parameters that govern the behavior of the anode PTL/CL interface is presented. Calculations are also combined with an experimental characterization of the thickness and electrical conductivity of an unsupported CL as a function of Ir loading. The results show that the in-plane electrical resistance at the anode PTL/CL interface plays a critical role in cell performance. Reaching an acceptable electrical resistance at low Ir loading (𝐿Ir ≃ 0.1 mgIr , cm−2) can be accomplished through the incorporation of a micrometer-sized microporous layer (MPL) onto the PTL or the preparation of bimodal CLs with a secondary conductive phase. Further reduction of the Ir loading to the ultra-low regime (𝐿Ir ≲ 0.1 mgIr , cm−2) may require the use of nanometer-sized MPLs with unsupported CLs or micrometer-sized MPLs with bimodal CLs. Furthermore, the decline of the volume reactive area at ultra-low Ir loading needs a maximization of the exchange current density and the specific electrochemical surface area, and a decrease of the catalyst oxygen coverage factor in the anode CL.