@article {1143, title = {Mechanistic understanding of pH effects on the oxygen evolution reaction}, journal = {Electrochimica Acta}, volume = {405}, year = {2022}, pages = {139810}, abstract = {The oxygen-evolution reaction (OER) is pivotal in many energy-conversion technologies as it is an important counter reaction to others that convert stable chemicals to higher-value products using electrochemistry. The local microenvironment and pH for the anode OER can vary from acidic to neutral to alkaline depending on the system being explored, making definitive mechanistic insights difficult. In this paper, we couple experiments, first-principles calculations based on density functional theory, microkinetics, and transport modeling to explore the entire pH range of the OER. At low current densities, neutral pH values unexpectedly perform better than the acidic and alkaline conditions, and this trend is reversed at higher current densities (> 20~mA cm-2). Using multiscale modeling, this switch is rationalized by a change from a dual-reaction mechanism to a single rate-determining step. The model also shows how the alkaline reaction rates dominate in the middle to high pH range. Furthermore, we explore that the local pH for near-neutral conditions is much different (e.g., 2.4 at the reaction surface vs. 9 in the bulk) than the pH extremes, demonstrating the criticality that transport phenomena plays in kinetic activity.}, keywords = {Electrochemistry, Microkinetics, Oxygen evolution reaction}, issn = {0013-4686}, doi = {https://doi.org/10.1016/j.electacta.2021.139810}, url = {https://www.sciencedirect.com/science/article/pii/S0013468621020934}, author = {Julie C. Fornaciari and Lien-Chun Weng and Shaun M. Alia and Cheng Zhan and Tuan Anh Pham and Alexis T. Bell and Tadashi Ogitsu and Nemanja Danilovic and Adam Z. Weber} } @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 {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 {1158, title = {Influence of Supporting Electrolyte on Hydroxide Exchange Membrane Water Electrolysis Performance: Anolyte}, journal = {Journal of The Electrochemical Society}, volume = {168}, year = {2021}, month = {08/2021}, pages = {084512}, abstract = {Hydroxide-exchange-membrane water electrolysis (HEMWE) is an emerging hydrogen-production pathway that combines many advantages of incumbent alkaline water electrolysis (AWE) and proton-exchange-membrane water electrolysis (PEMWE). Advancement in HEMWE has been accelerated with the development of stable and conductive hydroxide exchange membranes (HEMs) and a more comprehensive understanding of alkaline gas-evolving kinetics. However, performance and durability without supporting electrolytes (SELs) remain inferior to PEMWE and AWE and little is known about the role and impact of the SELs. This study investigates the effects of SELs used as anolyte solutions in HEMWEs including cation-type, anion-type, SEL conductivity and pH, presence of carbonates and increased cation/OH- ratios on cell voltage and stability. We report our findings that (i) cell potential and high-frequency resistance did not correlate with anolyte SEL conductivity, (ii) cation-type influences cell voltage at low current densities (<50 mA cm-2) as predicted by half-cell measurements, (iii) increased cation/OH- ratio causes increased overpotentials, and (iv) carbonates are exchanged in the HEM but removed via self-purging at high current density. Overall, this study concludes that concentrated KOH is still the best SEL.}, keywords = {hydrogen production pathway, Hydroxide exchange membrane, incumbent alkaline, proton exchange membrane, supporting electrolytes, water electrolysis}, doi = {10.1149/1945-7111/ac1dcd}, url = {https://doi.org/10.1149/1945-7111/ac1dcd}, author = {Aleksandr Kiessling and Julie C. Fornaciari and Grace Anderson and Xiong Peng and Andreas Gerstmayr and Michael R. Gerhardt and Samuel McKinney and Alexey Serov and Yu Seung Kim and Barr Zulevi and Adam Z. Weber and Nemanja Danilovic} } @article {796, title = {Integrated Membrane-Electrode-Assembly Photoelectrochemical Cell under Various Feed Conditions for Solar Water Splitting}, journal = {Journal of The Electrochemical Society}, volume = {166}, year = {2019}, note = {

{\textquoteright}doi: 10.1021/acsenergylett.0c01132\n - I.Am.Hydrogen{\textquoteright} {\textquoteright}\n - jyoungstrom{\textquoteright} {\textquoteright}Jason thinks this is great.\n\ \n - jyoungstrom{\textquoteright} {\textquoteright}\n - estechel{\textquoteright}

}, pages = {H3020-H3028}, issn = {0013-4651, 1945-7111}, doi = {10.1149/2.0041905jes}, url = {http://jes.ecsdl.org/lookup/doi/10.1149/2.0041905jes}, author = {Tobias A. Kistler and David Larson and Karl Walczak and Peter Agbo and Ian D. Sharp and Adam Z. Weber and Nemanja Danilovic} } @article {1097, title = {(Invited) HydroGEN: An AWSM Energy Materials Network}, journal = {ECS Transactions}, volume = {85}, year = {2018}, month = {05/2018}, pages = {3-14}, abstract = {

The HydroGEN (https://www.h2awsm.org/) energy materials network (EMN) aims to accelerate the research and development (R\&D) of advanced water splitting (AWS) technologies for clean, sustainable hydrogen production. Announced in October 2016, the HydroGEN EMN comprises six core National Laboratories and focuses on four AWS pathways: low- and high-temperature electrolysis, photoelectrochemical, and solar thermochemical water splitting. The HydroGEN consortium offers an extensive collection of materials research capabilities for addressing R\&D challenges in discovery and design, efficacy and efficiency, durability and cost. Leveraging the HydroGEN Consortium{\textquoteright}s technical experts and broad collection of unique resource capabilities is expected to advance the maturity and technology readiness levels in each advanced water splitting technology pathway.

}, issn = {1938-6737, 1938-5862}, doi = {10.1149/08511.0003ecst}, url = {http://ecst.ecsdl.org/content/85/11/3}, author = {James W. Vickers and Huyen N. Dinh and Katie Randolph and Adam Z. Weber and Anthony H. McDaniel and Richard Boardman and Tadashi Ogitsu and Hector Colon-Mercado and David Peterson and Eric L. Miller} }