Examinando por Autor "Lang, Jack Todd"

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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.