@article {1149, title = {Spatially resolved performance and degradation in a perfluorinated anion exchange membrane fuel cell}, journal = {Electrochimica Acta}, volume = {406}, year = {2022}, pages = {139812}, abstract = {Anion exchange membrane fuel cells may enable future operation with non-precious metal-based catalysts. These systems have a delicate sensitivity to operating conditions such as humidification levels and the presence of CO2 in the air oxidant stream. We present spatially resolved in-situ performance results that shed light on phenomena that are unique to anion exchange membrane fuel cells. For cell construction, a highly conductive perfluorinated anion exchange polymer was used as the membrane and the material in powder form as the ionomer. Experiments were conducted to investigate the effects of humidification, fuel/oxidant concentration, and carbonation effects on the performance and its distribution in the cell. The results indicated that (i) dry conditions at the cathode have a stronger effect than at the anode on overall cell performance, (ii) performance significantly suffered when humidification was below 90\%, (iii) fuel and oxidant dilution effects lead mass-transport losses and were stronger than flow rate effects, (iv) CO2 in the cathode feed stream creates an equilibration disparity between the inlet and outlet sections and CO2 purging is affected by flooding conditions, and (v) after >500~h of operation, performance deteriorates predominantly at the inlet.}, keywords = {2+1D fuel cell model, Anion Exchange membranes, Cathode dry-out, CO poisoning, Fuel cell durability, Mass transport limitations, Segmented fuel cell}, issn = {0013-4686}, doi = {https://doi.org/10.1016/j.electacta.2021.139812}, url = {https://www.sciencedirect.com/science/article/pii/S0013468621020958}, author = {Ashutosh G. Divekar and Michael R. Gerhardt and Christopher M. Antunes and Luigi Osmieri and Ami C. Yang-Neyerlin and Adam Z. Weber and Bryan S. Pivovar and Guido Bender and Andrew M. Herring} } @article {1151, title = {A comprehensive modeling method for proton exchange membrane electrolyzer development}, journal = {International Journal of Hydrogen Energy}, volume = {46}, year = {2021}, note = {Special issue on the 2nd International Symposium on Hydrogen Energy and Energy Technologies (HEET 2019)}, pages = {17627-17643}, abstract = {Hydrogen attracts significant interests as an effective energy carrier that can be derived from renewable sources. Hydrogen production using a proton-exchange membrane (PEM) electrolyzer can efficiently convert renewable power via water splitting in wide scales{\textemdash}from large, centralized generation to on-site production. Mathematical models with multiple scales and fidelities facilitate the continuing improvements of PEM electrolyzer development to improve performance, cost, and reliability. The model scopes and methods are presented in this paper, which also introduces a comprehensive PEM electrolysis modeling tool based on computational fluid dynamics (CFD) software, ANSYS/Fluent. The modeling tool incorporates electrochemical model of a PEM electrolysis cell to simulate the performance of coupled thermal-fluid, species transport, and electrochemical processes in a product-scale cell or stack by leveraging the powerful meshing generation and CFD solver of ANSYS/Fluent. The thermal-fluid modeling includes liquid water/gas two-phase flow and simulates a PEM electrolysis cell by using Fluent user-defined functions as add-on modules accounting for PEM-specific species transport and electrochemical processes. The modeling outcomes expediate PEM electrolyzer scaling up from basic material development and laboratory testing.}, keywords = {Electrochemical modeling, Hydrogen production, Low temperature electrolysis water splitting, Proton exchange membrane electrolysis cell}, issn = {0360-3199}, doi = {https://doi.org/10.1016/j.ijhydene.2021.02.170}, url = {https://www.sciencedirect.com/science/article/pii/S0360319921007448}, author = {Zhiwen Ma and Liam Witteman and Jacob A. Wrubel and Guido Bender} } @article {1155, title = {Elucidating the Role of Hydroxide Electrolyte on Anion-Exchange-Membrane Water Electrolyzer Performance}, journal = {Journal of The Electrochemical Society}, volume = {168}, year = {2021}, month = {05/2021}, pages = {054522}, abstract = {Many solid-state devices, especially those requiring anion conduction, often add a supporting electrolyte to enable efficient operation. The prototypical case is that of anion-exchange-membrane water electrolyzers (AEMWEs), where addition of an alkali metal solution improves performance. However, the specific mechanism of this performance improvement is currently unknown. This work investigates the functionality of the alkali metal solution in AEMWEs using experiments and mathematical models. The results show that additional hydroxide plays a key role not only in ohmic resistance of the membrane and catalyst layer but also in the reaction kinetics. The modeling suggests that the added liquid electrolyte creates an additional electrochemical interface with the electrocatalyst that provides ion-transport pathways and distributes product gas bubbles; the total effective electrochemical active surface area in the cell with 1 M KOH is 5 times higher than that of the cell with DI water. In the cell with 1 M KOH, more than 80\% of the reaction current is associate with the liquid electrolyte. These results indicate the importance of high pH of electrolyte and catalyst/electrolyte interface in AEMWEs. The understanding of the functionality of the alkali metal solution presented in this study should help guide the design and optimization of AEMWEs.}, keywords = {alkali metal solutions, anion-exchange-membrane water electrolyzers, Energy Sciences, energy storage, liquid electrolyte, solid-state devices}, issn = {0013-4651}, doi = {10.1149/1945-7111/ac0019}, author = {Jiangjin Liu and Zhenye Kang and Dongguo Li and Magnolia Pak and Shaun M. Alia and Cy Fujimoto and Guido Bender and Yu Seung Kim and Adam Z. Weber} } @article {1067, title = {Investigation of porous transport layer parameters for proton exchange membrane water electrolysis}, year = {2019}, abstract = {
  1. Presentation
  2. Investigation of porous transport layer parameters for proton exchange membrane water electrolysis
  3. Presenter
    Zhenye Kang
  4. Contributor
    Shaun M. Alia
  5. Contributor
    James L. Young
  6. Contributor
    Guido Bender
  7. LTE
  8. 2019
  9. Hilton Atlanta, Atlanta, GA, USA
  10. 236th ECS Meeting
  11. http://ma.ecsdl.org/content/MA2019-02/37/1747.short
  12. 11/6/2019, 10:47:45 AM
  13. 12/6/2019, 1:28:14 PM
Abstract
Published on October 17th, 2019 Hydrogen production through proton exchange membrane water electrolysis (PEMWE) is regarded as a very promising technology that offers a highly efficient and robust path to store electrical energy in form of hydrogen and further enables the integration of renewable energy into the electrical grid 1-3. The total cell voltage of a single PEM water electrolyzer cell is composed of the open circuit voltage, activation overpotential, diffusion overpotential, and ohmic loss overpotential 4. The total voltage of the cell can be expressed as Eq(1) 5. V=V_OCV+V_act+V_ohm+V_diff (1) Where V_OCV is the Nernst potential which is also called the reversible voltage and can be calculated from the Nernst equation or Gibbs free energy, V_act is the activation overpotential due to the electrochemical reaction and it represents the overpotential to drive the electron transfer and electrochemical reaction kinetics as described by the Butler-Volmer model, V_ohm is the ohmic overpotential caused by the resistances of the electronic/ionic components and interfacial contact resistances, and V_diff is the diffusion overpotential related to mass transport. Porous transport layers (PTLs) are key components in PEMWE. They facilitate mass transport, thermal and electrical conduction, and are required to sustain a good contact with adjacent components 6-8. It is expected that various PTLs with different structures and wettability exhibit nonidentical performance in PEMWE. In this study, a general model is established to investigate the PTL parameters of four inherently different PTLs, including non-treated Toray paper, PTFE treated Toray paper, sintered titanium particles and Ti felt. SEM images highlighting the structures of these PTL materials are shown in Figure 1. The materials, which differed in thickness, porosity, material and composition were evaluated with identical MEAs over a range of operating conditions for model validation. The resulting data indicate that the hydrophobic additives in the Toray paper will decrease the PEMWE performance due to increased mass transport loss and ohmic loss. Ti felt with similar thickness and porosity as non-treated Toray paper showed slightly reduced performance due to its higher ohmic loss. Sintered Ti particle PTLs exhibit much higher ohmic resistance than Ti felt and nontreated Toray paper, which may be attributed to its significantly larger thickness and/or an increased contact resistance. The experimental data was employed to validate the MATLAB/Simulink model which enables the simulation of the contribution of each overpotential. The model was used to successfully describe the effects of PTFE loading on PEMWE performance, as shown in Figure 2. The hydrophobic treatment resulted, as expected, in detrimental performance effects. The diffusion loss of a 20\% PTFE treated Toray paper is significantly higher than that of the nontreated PTLs (Figure 2). The modeling results also indicate that the change of the wettability of the PTLs by hydrophobic additives/agents, impacted not only the diffusion loss significantly, but also affected the ohmic loss and activation loss. This was specifically detrimental to PEMWE cell performance when operating at high current densities. The model that was validated in this study can be used to predict the effects of key PTL parameters and utilized to optimize PEMWE performance.
}, url = {http://ma.ecsdl.org/content/MA2019-02/37/1747.short}, author = {Zhenye Kang and Shaun M. Alia and James L. Young and Guido Bender} } @article {1069, title = {Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers}, journal = {Electrochemistry Communications}, volume = {97}, year = {2018}, month = {12/2018}, pages = {96-99}, abstract = {

Published on December 1st, 2018. Titanium-based porous transport layers (PTL) used in polymer electrolyte membrane (PEM) water electrolyzers suffer from surface passivation (titanium oxidation), which increases the interface resistance between the PTL and electrode. For long-term operation, PTLs are typically coated with considerable amounts of platinum or gold to ensure reasonable performance profiles over time. Moreover, it is well known that the oxide forms of platinum and gold are not stable under electrolysis conditions. In this study, an easy and scalable method is introduced to protect the titanium PTL from passivation by sputtering very thin layers of iridium onto commercially-available titanium PTLs. The iridium layer reduces the overall ohmic resistance of the PTL/catalyst layer interface and improves the cell{\textquoteright}s performance to that achieved with carbon-based PTLs. The coating process homogeneously deposited iridium throughout the inner structure of the PTL. The findings of this study may lead to the use of iridium as a protective layer for titanium PTLs, potentially enable operation at increased cell voltages and lead to increased electrolyzer durability.

}, issn = {1388-2481}, doi = {10.1016/j.elecom.2018.10.021}, url = {http://www.sciencedirect.com/science/article/pii/S1388248118302741}, author = {Chang Liu and Marcelo Carmo and Guido Bender and Andreas Everwand and Thomas Lickert and James L. Young and Tom Smolinka and Detlef Stolten and Werner Lehnert} }