bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Characterization of Microporous Layers on Porous Transport Layers for Proton Exchange Membrane Water Electrolyzers
Authors: Ouimet Ryan J. , Fortiner Serafina , Kulkarni Devashish , Zenyuk Iryna , Erb Bryan , Smeltz Andrew , Capuano Christopher 
Published: September 2023

Porous transport layers (PTLs) serve many important functions for proton exchange membrane water electrolyzers. PTLs facilitate fluid transport towards and away from the anode catalyst layer, act as a mechanical support for the membrane, and provide electrical contact with the anode catalyst layer [1]. As a result, PTLs can greatly impact cell performance. However, while there has been an effort to improve similar gas diffusion layers in PEM fuel cells, there has not been a significant effort to optimize the overall form factor and design of PTLs for PEM water electrolyzers.
One of the primary concerns about the current design of PEM water electrolyzer PTLs is how they interact with the anode catalyst layer. In order to ensure proper fluid transport through the PTL, there is significant porosity throughout the PTL including at the anode interface. The large porosity and particle sizes of the PTL can cause heterogeneous contact of the PTL and catalyst layer thus reducing the catalyst utilization. Therefore, high catalyst loadings are required to obtain acceptable performance and durability. One method to address this concern would be to develop a metal microporous layer (MPL) that can be integrated onto a PTL at the anode interface that can withstand the high potentials at the anode while maintaining sufficient fluid transport. The MPL is fabricated using smaller metal particle sizes compared to the bulk PTL, which results in smaller pores creating a more uniform surface. The uniform surface and small pore sizes of the MPL provide a much higher interfacial contact area at the anode interface compared to a traditional PTL and would allow for a more uniform contact pressure across the anode interface. Higher interfacial contact will improve catalyst utilization and facilitate the reduction in anode catalyst loading, leading to reductions in overall electrolyzer capital cost [2].
In this work, prototype PTLs with metal MPLs are developed and tuned for optimal PEM water electrolyzer cell performance. The prototype PTLs with MPLs are characterized to understand how specific properties (thickness, porosity, tortuosity, etc.) influence cell performance. Electrochemical testing shows that adding an MPL at the anode/PTL interface can allow for acceptable cell performance with 90% lower anode catalyst loading compared to when using a baseline PTL.

References

[1] X.-Z. Yuan, N. Shaigan, C. Song, M. Aujla, V. Neburchilov, J.T.H. Kwan, D. P. Wilkinson, A. Bazylak, K. Fatih. The porous transport layer in proton exchange membrane water electrolysis: perspectives on a complex component. Sustainable Energy & Fuels, 6, (2022), 1824-1853.
[2] T. Schuler, J.M. Ciccone, B. Krentcher, F. Marone, C. Peter, T.J. Schmidt, F.N. Büchi. Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis. Advanced Energy Materials, 10, (2019), 1903216
Cathode Dry Operation of Anion Exchange Membrane Water Electrolysis
Authors: Ito Hiroshi , Wang Ruixiang , Hirose Riku , Kageyama Akane , Ishida Masayoshi , Ohashi Masato 
Published: September 2023

The scale of hydrogen production from renewable energy sources is expected to increase worldwide in the future. Water electrolysis is a practical way to produce hydrogen from renewable energy sources. Water electrolyzers that use an anion exchange membrane (AEM) are expected to be new devices for hydrogen (H2) production that achieve high performance at low capital cost.
In AEM water electrolysis, “cathode dry operation” is sometimes applied. In this operation mode, water (electrolyte solution) is supplied only to the anode, not to the cathode where water is consumed in the reaction, keeping the cathode dry. In this way, relatively dry hydrogen can be extracted directly from the cathode, simplifying the hydrogen drying process. When water electrolyzers are installed in large quantities (over 1000 units), the cost of balance of plants (BOPs) is expected to account for the majority of system costs [1], and simplifying the BOPs are important for reducing system costs. However, it was observed that cathode dry operation would cause concentration overpotentials due to water diffusion through the membrane [2], which may limit the current density and membrane thickness to prevent cathode dry-out.
In this study, the effects of electrolyte composition and concentration on the water behavior in the membrane during cathodic dry operation on the electrolysis performance were quantitatively investigated.
AcknowledgementThis work was supported partly by the New Energy and Industrial Development Organization (NEDO) through the Advancement of Hydrogen Technologies and Utilization Project (P 14021). The authors wish to express their gratitude to Tokuyama Corporation for their support and helpful advice.
References
[1] Mayyas et al. Manufacturing cost analysis for proton exchange membrane water electrolyzers, NREL Technical report, NREL/TP-6A20-72740 (2019).
[2] R. Wang et al, Int. J. Hydrog. Energy, 47, 40835 (2022).
(Invited) Catalysts, Inks and Electrodes for PEM Water Electrolysis: Scalable Approach for Highly Performed Catalyst Layer Fabrication
Authors: Serov Alexey , Lyu Xiang , Creel Erin , Yu Haoran , Cullen David A. , Kariuki Nancy N. , Park Jaehyung , Myers Deborah J. , Rice Robin , Padgett Elliot , Mauger Scott A , Bender Guido , Foster Jayson , Pylypenko Svitlana 
Published: September 2023

The majority of commercially available anodic electrocatalysts for Low Temperature PEM Water Electrolyzers are based on unsupported iridium-based materials. These electrocatalysts can be amorphous or crystalline metallic, oxidic, and/or hydroxide-derived compounds. The planned worldwide installations of electrolyzers (on the order of tens of Gigawatts per year) will require manufacturing of Membrane Electrode Assemblies (MEAs) via highly scalable methods, one of which is Roll-2-Roll production (R2R) [1, 2]. In contrast to spraying techniques, R2R requires the utilization of inks with a higher content of solids, which in the case of extremely dense Ir-based materials may cause a sedimentation of suspended electrocatalysts resulting in overall ink destabilization.
In the presented work a systematic study of ink stability with commercial IrO2 catalysts over a period of 14 days was performed. During this period of time the minimal redispersion of slurries was done to mimic realistic conditions of inks aging. The inks were comprehensively characterized by rheological measurements, zeta potential, particle size distribution (Dynamic Light Scattering) and inks density. A series of decal electrodes was fabricated using Baker bar coating approach (a model of R2R production) and coatings were characterized by contact angle, X-Ray Photoelectron Spectroscopy and Transmission Electron Microscopy.
Detailed electrochemical performance analysis including the separation of voltage losses [3] via Electrochemical Impedance Spectroscopy was performed to compare MEA performance with aging time.

Acknowledgements and Statements.

The authors acknowledge financial support from M2FCT and H2NEW consortia.

References.

[1] J. Sharma, X. Lyu, T. Reshetenko, G. Polizos, K. Livingston, J. Li, D. L. Wood, A. Serov "Catalyst layer formulations for slot-die coating of PEM fuel cell electrodes" Int. Journal of Hydrogen Energy 47 (2022) 35838-3585.
[2] E. B. Creel, K. Tjiptowidjojo, J. A. Lee, K. M. Livingston, P. R. Schunk, N. S. Bell, A. Serov, D. L. Wood III "Slot-Die-Coating Operability Windows for Polymer Electrolyte Membrane Fuel Cell Cathode Catalyst Layers" J. of Colloid and Interface Science 610 (2022) 474-485.
[3] A. Dizon et. al “Advanced Voltage Break Down Analysis by Statistical Open-Source Tool Case Study Based on Polymer Electrolyte Water Electrolysis”, ECS Abstract 242 (2022)
Formation of Oxygen Vacancy Gradient TiO2 Via Photoelectrochemical-Driven “Self-Purification” Process
Authors: Kim Kwang Hee , Park Jong Hyeok 
Published: September 2023

Solar water splitting by oxide semiconductors is the most ideal strategy for clean and sustainable hydrogen production. However, the application of oxide semiconductors is limited by their poor charge separation efficiency, which results from the short diffusion length of minority carriers and bulk charge recombination. Oxygen vacancy (Vo) is a unique and crucial tool in the metal oxide semiconductor, which not only is one of the intrinsic defects but plays a significant role to modulate their optical, physical, and catalytic properties. For instance, the introduction of oxygen vacancy can suppress electron-hole recombination for efficient solar water splitting. However, it remains challenging to control oxygen vacancies due to their random formation and moving in the lattice of the nanostructure.
In this work, we present a photoelectrochemical (PEC) driven “self-purification” approach for the formation of oxygen vacancy gradient (ΔVo) by reconstructing the disorder overlayer from the TiO2 nanowire photoanode under long-term PEC operation using “self-purification” mechanism. The presence of Vo in oxygen vacancy gradient TiO2 (ΔVo-TiO2) was clearly confirmed by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) spectra. Also, high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS) analysis showed that the gradient distribution of Vo forms in ~9.5 nm-thickness range of ΔVo-TiO2.

After the “self-purification” process, the photocurrent density of ΔVo-TiO2 doubles compared to that of pristine TiO2 at the 1.23 V vs RHE. Also, we demonstrated that Vo improved the charge separation in bulk region by charge carrier dynamics with time-correlated single-photon counting (TCSPC) analysis. Furthermore, ΔVo-TiO2 exhibits ~95% charge transport efficiency, which is associated with bulk recombination. These results indicate the ~95% photon within the absorption range can be converted to charge. Lastly, we verified the electronic structure of ΔVo-TiO2 by density functional theory (DFT) calculations. ΔVo-TiO2 forms a cascade of energy gradients along the bulk region, which can polarize the charges to form a built-in electric field that thermodynamically boosts charge carrier migration and suppresses bulk charge recombination.
In conclusion, we suppose that the key role of Vo in the bulk region in a metal oxide photoanode is critical to enhancing charge separation in TiO2. Therefore, our demonstration can fully resolve the conventional efforts to establish the optimized Vo for photocatalyst and offer a feasible approach for gradient doping semiconductors synthesis.
Mechanisms for Charge Selectivity on Semiconducting Photocatalyst Particles
Authors: Kaufman Aaron James , Shen Meikun , Boettcher Shannon W. 
Published: September 2023

Overall-water splitting on photocatalysts provides a direct-unassisted path in the conversion of solar energy to chemical energy. Optoelectronic properties (absorbing incident light with long excited state lifetimes) and carrier selective contacts (transporting and transferring the desired electronic carrier to the targeted redox active species) are two key parameters that govern photocatalyst behavior. However, the advantageous small geometry of the highest achieving photocatalysts makes measurement of their carrier selective contacts difficult. Additionally, several mechanisms that enable high energy-conversion efficiencies and large gradients in free energy manifest only at the nanoscale at individual nanoparticle sites. SrTiO3 has been extensively studied and shown to split water with high quantum yields when decorated with HER and OER catalysts. SrTiO3 is used, in this work, as a model system to study mechanisms for charge selectivity on overall-water splitting photocatalyst particles.
Here, we use three sample geometries to measure local, facet, and catalyst-dependent, electrochemical driving forces and their synergistic enhancement of carrier selectivity, (single crystal planar (b), single crystal co-facet exposed planar (a), facetted nanoparticles (c) loaded with OER and HER catalysts [{Pt/CrO3, Rh/CrO3} and CoOOH respectively]). We use ex-situ conductive atomic force microscopy to individually interrogate the electrical properties of nano-scale catalyst/semiconductor junctions decorated on facet-engineered surfaces of SrTiO3. Supporting experiments of SECM and Operando AP-XPS will be used to measure the charge carrier selectivity when an electrolyte is present and connect the ex-situ characterization observations to operando conditions. In summary, these findings demonstrate the underlying mechanisms and the degree that they play, enabling directed research of photocatalyst systems under the two dominant engineering conditions, high optoelectronic properties and charge selective contacts.

Figure 1
Catalyst Support Interactions of Highly Active Nife-LDH Towards the Implementation in Photoelectrochemical and Sea-Water Based Water Splitting Technologies
Authors: Buchheister Paul Wolfgang , Gort Christopher , Klingenhof Malte , Kaiser Bernhard , Strasser Peter 
Published: September 2023

For the implementation in photoelectrochemical (PEC) and sea-water based water splitting devices it is of utmost importance to find stable substrates that do not degrade under application related potentials and illumination. While PEC devices incorporate an absorber that has to be protected from the harsh conditions in the electrolyte, the prevalence of Cl- ions in sea-water based water splitting devices leads to corrosion of most metallic substrates under application related potentials. Catalyst coated TiO2 substrates are therefore used as protection layers in PEC devices, while titanium porous transport layers show great stability in anionic exchange membrane sea-water splitting devices.
In this study we investigated the interaction between state-of-the-art NiFe-LDH as a catalyst for the OER and titanium substrates. It was shown that the activity of NiFe-LDH on bare Ti/TiOx substrates was very poor. Through the incorporation of thin metal interlayers (Au, Ni) an increase in current density by two orders of magnitude could be observed. Through detailed XPS measurements before and after electrochemical activation of the electrodes we were able to show an improved transformation of the as prepared catalyst into the highly active (oxo)hydroxide phase for the gold and nickel sputtered titanium electrodes. An accelerated stress test performed on these electrodes showed a stable behavior for most electrode assemblies, with Nickel interlayers showing great promise for PEC devices. From our experiments we exclude a pure conductivity enhancement as possible explanation, but instead propose an additional change in the local atomic and electronic structure at the metal-support and metal-catalyst interfaces.
A Conversion Type Iron Anode for High-Areal-Capacity Hybrid Redox Flow Batteries
Authors: SHI Yang , Lu Yi-Chun 
Published: September 2023

Redox flow battery (RFB) is one of the most promising technologies for energy storage owing to its advantages of high safety, high efficiency, and low cost.1 Hybrid RFBs such as Zn-based RFBs offer a much higher energy density compared to all liquid RFBs. However, they rely on metal dissolution/deposition electrodes, which suffer from severe dendrite issues and poor reversibility, especially at high areal capacity and high current density. These inherent challenges of metal electrodes preclude their practical deployment for large-scale and long-duration energy storage applications.
To break from this intrinsic limitation, in this work, we exploited a high-loading conversion electrodes to replace metal deposition electrodes to achieve high cycling stability at high areal capacity/current density for hybrid RFBs. With this strategy, using Fe3O4/Fe(OH)2 conversion negative electrode as an example coupling with ferricyanide/ferrocyanide positive electrode, we demonstrated conversion type all-iron hybrid RFBs with an unprecedented high cycling areal capacity of 126.6 mAh cm–2 at 50 mA cm–2 for 200 cycles (1000 hours) and 215 mAh cm–2 at 60 mA cm–2 for 100 cycles (700 hours) without capacity decay.2 The conversion electrode eliminates the dendrite issues and limitations on metal areal capacity, demonstrating unprecedented high cycling areal capacity and current density compared to conventional dissolution/deposition zinc metal negative electrode. We will discuss the compositional/morphological stability of the Fe3O4/Fe(OH)2 conversion iron negative electrode during the hybrid RFB operation and the techno-economic analysis of developed conversion type all-iron hybrid RFB for practical applications.

Acknowledgment:

The work described herein was supported by a grant from the Research Grant Council (RGC) of the Hong Kong Special Administrative Region, China (project no. C1002-21G).

Reference:

(1) Yao, Y. X.; Lei, J. F.; Shi, Y.; Ai, F.; Lu, Y. C. Assessment methods and performance metrics for redox flow batteries. Nat. Energy
2021,
6 (6), 582.
(2) Shi, Y.; Wang, Z.; Yao, Y.; Wang, W.; Lu, Y.-C. High-Areal-Capacity Conversion Type Iron-Based Hybrid Redox Flow Batteries. Energy Environ. Sci.
2021, 10.1039/D1EE02258J.
Development of Cost-Effective Membranes for Redox-Flow Batteries
Authors: Yang Guang , Lehmann Michelle , Self Ethan , Sacci Robert L , Saito Tomonori , Nanda Jagjit 
Published: September 2023

Developing long-duration energy storage (LDES) systems is key to promoting the penetration of intermittent energy storage, such as solar and wind into the electric grid. DOE’s Long Duration Storage Shot establishes a target to reduce the cost of grid-scale energy storage by 90% for systems with durations of >10 hours. Non-aqueous RFBs (non-aqueous RFB) using earth-abundant materials are promising to fulfill this target. A key bottleneck to keeping RFB from market penetration is the lack of high-performance and cost-effective membranes. Membranes represent the most critical component in non-aqueous RFB, and they are decisive to the cell stack performance and cost. For example, the ionic conductivity of the membrane determines the power density of the RFBs, while ion selectivity and solvent uptake govern non-aqueous RFB cycle life. Herein, we will present recent progress in our team on the membrane development for the non-aqueous flow batteries.
The ionic conductivity - mechanical strength tradeoff is a long-standing challenge for all polymer electrolyte development. In a redox flow battery, solvent uptake promotes membrane ionic conductivity but decreases its storage modulus due to the increased polymer chain relaxation. Two strategies are found effective to alleviate such a tradeoff i) selective plasticization of the ion-conductive block such as poly(ethylene oxide) (PEO) in a polystyrene (PS)− PEO−PS block copolymer (SEO) electroconductivity by glyme-type of solvent, and ii) enhancement of the membrane mechanical strength by creating hydrogen and ionic bonds between the polymer matrix and the inorganic scaffold. Mitigating redox-active species crossover poses another challenge in membrane design. We show that the cation exchanged single ion conducting membrane can effectively decrease the crossover of the polysulfide species in a Na metal – polysulfide hybrid flow battery, which promotes the RFB capacity retention, Columbia efficiency, and cycle life benchmarked to a commercial porous membrane.

Acknowledgment

This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program led by Dr. Imre Gyuk, in the Office of Electricity.
Higher Energy Density Mediated Lithium-Sulfur Flow Batteries
Authors: Meyerson Melissa L , Maraschky Adam M. , Small Leo J. 
Published: September 2023

There is a need for safe, reliable, high-capacity storage for long duration energy storage. The low cost and high specific capacity of sulfur make Li-S batteries ideal for this purpose. However, sulfur has poor electrical conductivity and Li-S batteries are prone to polysulfide shuttling that decreases the battery life. Additionally, lithium metal cannot be cycled at high rates or dendritic growth is produced. We have previously addressed the issues with the S by combining aspects of a static Li-S battery with aspects of a redox targeting system and flow battery. With this system we demonstrated that fundamental Li-S chemistry and novel SEI engineering strategies can be adapted to the hybrid redox flow battery architecture, obviating the need for ion-selective membranes or flowing carbon additives, and offering a potential pathway for inexpensive, scalable, and safe MWh scale Li-S energy storage. Here we present two key improvements to the system: (i) scaled up sulfur loading from 2.5 mgs cm-2 to over 50 mgs cm-2 (increasing energy density), and (ii) increased current density from 0.5 mA cm-2 to 10 mA cm-2 (increasing power density). Additionally, we are able to assemble the battery in the discharged state, improving the safety and decreasing manufacturing costs.
To implement these improvements, we address the limitations due to the formation of dendrites on the Li metal anode. We first tested high surface area scaffolds in Swagelok cells to examine the effect of the increased effective surface area and seeding with lithiophilic materials like ZnO on Li metal deposition independent of the flow cell or S chemistry. Using a high effective surface area scaffold enabled increasing the applied current density from 0.5 mA cm-2 to 10 mA cm-2, increasing the cycling rate by 20x. Furthermore, the addition of a lithiophilic seed layer decreases the nucleation overpotential and encourages uniform Li electrodeposition. A tailored flow field also increases the uniformity of Li deposition on the anode by enhancing the uniformity of the catholyte flow velocity. These modifications are first evaluated separately and then combined in a mediated Li-S flow battery where cycling rate and capacity retention are compared against a traditional planar Li anode and open flow field.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Studying Crack Formation in Catalyst Layer Films for Proton Exchange Membrane Fuel Cells
Authors: Liu Jiawei , Plymill Austin , Blackburn Scott , Park Andrew M , Litster Shawn 
Published: September 2023

The performance and durability of proton exchange membrane fuel cells (PEMFCs) can be affected by cracks formed in catalyst layers (CLs). While previous research has shown that CLs prepared with pre-commercial high oxygen permeability ionomer (HOPI) are more efficient and durable, they can lead to significantly more cracking features than CLs prepared with traditional perfluorosulfonic acid (PFSA) ionomer. Therefore, it is important to reduce cracking to further improve cathode performance, durability, and film quality. With this goal in mind, we analyzed ink drying and crack formation during the wet-film coating process via imaging with an optical microscope fixed above a film applicator. Transient quantitative crack growth studies were performed to evaluate the dynamic nature of the process. Alongside that, the crack density of post-coating films was quantified at higher resolutions using a compound microscope. Ink composition, Pt-based catalysts and relative humidity of drying environment were varied in order to understand which combinations resulted in fewer cracks.
This material is based upon work supported by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Fuel Cell Technologies Office, Award Number DE-EE0008822.