bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of a Passive Osmosis-Integrated Electrolyzer for Seawater Electrolysis
Authors: Ghasemi Masoomeh , Al Murisi Mohammed , Mustain William Earl , Shimpalee Sirivatch
Published: August 2024

The requirement for extremely pure water in electrolysis, combined with the abundant presence of seawater, has prompted extensive research into the creation of direct seawater electrolysis technology for decades [1]. However, these efforts have had limited success due to other limiting issues that arise, including competition with the chloring evolution reaction, increased membrane resistance, corrosion of electrode materials and electrode scaling due to the presence of multivalent cations. To avoid these issues, seawater is typically first desalinated using reverse osmosis, but that comes with additional energy cost. Therefore, our project has proposed a new reactor that integrates passive osmosis (extracting fresh water from seawater) with electrolysis.

In this presentation, we will discuss the operation of the osmosis-integrated electrolyzer and show theoretical predictions of the osmotic pressure differential and water flux/velocity profiles under different conditions. The numerical model that will be presented was applied to three different cell designs that have been physically developed. The first cell consists of two anion exchange membranes (AEMs) with two side chambers containing KOH and a middle chamber containing Sodium Chloride (NaCl). The second cell has KOH in one outer compartment and H2SO4 in the other. The central compartment containing NaCl is separated from KOH compartment by an AEM and the H2SO4 compartment by a cation exchange membrane (CEM). The third cell eliminates the central compartment and allows the osmosis to occur outside of the cell.

The simulation results show that by increasing the concentration of KOH and H2SO4 in the side chambers for all three models, the amount of water transferred from the middle chamber, containing of NaCl to the side chambers increases. The simulation results were validated by experiments (Figure 1). In addition, the model is able to quantify the transport of ions in the system, including chloride ions through the AEM. Lastly, the mass transfer model is integrated with an electrochemical model where an anode and cathode are added to the system to consume the water that is transported through the membranes.

Reference:

[1] M. A. Khan, T. Al-Attas, S. Roy, M. M. Rahman, N. Ghaffour, V. Thangadurai, S. Larter, J. Hu, P. M. Ajayan, and M. G. Kibria, “Seawater electrolysis for hydrogen production: a solution looking for a problem?” Energy & Environmental Science, 14, 4831 (2021).

Figure 1
(Invited) Overview of Ion-Conducting Polymer Membranes and Membrane Separators for Water Electrolysis
Authors: Bae Chulsung
Published: August 2024

Traditional liquid alkaline electrolyzer uses a porous diaphragm to allow diffusion of hydroxide ion from a feed of concentrated KOH solution while separating anode and cathode and suppressing mixing of produced H2 and O2 gases. Although liquid alkaline electrolyzer is considered as a matured technology, recent renaissance of new electrode separators suggests there is significant potential for improvement in efficiency and cost reduction by lowering area specific resistance and increasing operation current density.

Ion-conducting polymers (e.g., proton or hydroxide) are used as a key component of polymer electrolyte membranes, such as acidic proton exchange membrane (PEM) and alkaline anion exchange membrane (AEM), in electrochemical energy conversion and storage technologies including water electrolyzers. For example, the state-of-the-art PEM electrolyzers have used Nafion for a PEM and ionomer catalyst binder for decades, though it is not ideal proton-conducting membrane material for those applications. Recent pressure on perfluoroalkyl substrates (PFASs) from government and environmental activist groups due to their environmental and health hazard has attracted the development of alternative polymer electrolyte membranes based on hydrocarbon polymers within electrochemical society. Compared to perfluorosulfonated Nafion, hydrocarbon ion-conducting polymers (both PEMs and AEMs) can offer advantages of flexible synthetic tunability, lower gas permeability, and importantly lower production cost.

In this tutorial, an overview of recent progress in the development of advanced porous membrane separators, PEMs and AEMs, their key membrane properties, and the state-of-the-art performance in applications of water electrolyzers will be discussed.

Figure 1
Evaluating the Impact of Cell Assembly and Operating Conditions on the Performance of Anion Exchange Membrane Electrolyzers
Authors: Amirsalehi Mahmoud , Gopi K Hari , Satjaritanun Pongsarun , Moreno Marta , Britton Benjamin , Mustain William Earl
Published: August 2024

The alkaline water electrolyzer (AWE) and proton exchange membrane water electrolyzer (PEMWE) are the two dominant commercial platforms to produce hydrogen through electrolysis. Recent efforts have focused on combining the benefits of the two technologies, leading to the creation of the anion exchange membrane water electrolyzer (AEMWE). AEMWEs operate under high pH conditions, like AWEs, enabling the use of cost-effective materials as cell components and non-noble electrocatalysts. AEMWEs also utilize the same high-performance zero-gap design PEMWEs and also have the ability to operate at high differential pressures. Therefore, AEMWEs offer the opportunity to optimize both cost and performance, out-pacing both incumbent technologies after further development.

As the “active” materials in AEMWEs, the anion exchange membranes and ionomers and the catalysts have been widely studied and a number of materials have been proposed and reported on in the literature and throughout the last several ECS meetings. However, such materials are only one piece of the overall puzzle when it comes to the operation of AEMWEs. There are several aspects of cell assembly and operation that go a long way to dictating the performance of an operating cell.

Therefore, the overarching goal of this study was to investigate several operational variables for AEMWEs with a known high-quality set of anion-exchange materials, known commercially as Aemion+™ paired with commercially available catalysts – PtNi/C at the cathode and either IrOx or NiFeOx at the anode. For cell assembly, representative variables that were changed were the type of membrane and electrode pre-treatment, gasket thickness, cell torque and membrane thickness. Operationally, temperature, current density and break-in procedure were adjusted. This talk will link each of these variables to the polarization performance and galvanostatic durability
Quantification of Hydrogen and Transition Metals in the Cathode Catalyst Layer of Anion Exchange Membrane Electrolyzer By Ion Beam Techniques
Authors: Kumaran Yamini , Chaudhary Latika S. , Gherasoiu Iulian , Moreno Jimenez Daniel Alejandro , Kim Kyoung-Yeol , Kumaran Yamini
Published: August 2024

Anion Exchange Membrane Water Electrolyzer (AEMWE) has increased interest in H2 production at low cost and high scalability. The efficiency is strongly dependent on the membrane electrode assembly (MEA) with appropriate ionomer and catalyst layers. Herein, we report AEMWE with MoNi4-MoO2 cathode catalyst layer in ionomer-free Catalyst Coated Substrate (CCS) configuration. The optimized MEA for AEMWE demonstrated the superior performance of 225 mA/cm2 at 2V with more than 48 hours of durability. The X-ray diffraction confirmed the NiMoO4 phase transformation to MoNi4-MoO2 and SEM-EDS was used to study the morphology and elemental composition of the deposited catalyst. X-ray photoelectron Spectroscopy demonstrated the dominant metallic MoO2 formed after H2/Ar annealing. Rutherford Backscattering Spectroscopy (RBS) was also employed to measure the depth composition profile of the catalyst layer exhibiting the reduction of Ni concentration in the bulk after annealing. Further, we introduce hydrogen depth profiling by Nuclear Reaction Analysis (NRA) via the resonant 1H(15N,αγ)12C reaction as a versatile method for the highly depth-resolved visualization of hydrogen(H) in the near-surface region, including transitions of hydrogen between the surface and the bulk, and between shallow interfaces of the nanostructured cathode catalyst layer. The diffusion of the H atoms was observed with a 40% atomic percent of Hydrogen after H2/Ar annealing of the catalyst for 180 minutes (about 3 hours) and decreased to 10% atomic percent of hydrogen after 24 hours of electrolyzer operation. This technique also enabled the measurement of the zero-point vibrational energy of hydrogen atoms absorbed on the surfaces of the catalyst layer. Overall, this work better explains the cathode catalyst degradation effects and hydrogen diffusion in the cathode catalyst layer responsible for voltage and mass transfer losses in AEM electrolyzers.
Investigating Water and Ion Transport in a Novel Cell Design for Seawater Electrolysis
Authors: Al Murisi Mohammed , Ghasemi Masoomeh , Ali Rashad , Yang Xiaoxuan , Bimbatti Yasmin , McCutcheon Jeffrey , Kohl Paul , Shimpalee Sirivatch , Mustain William Earl
Published: August 2024

With increasing concerns about the climate change associated with the carbon dioxide emission from utilizing traditional fuels, hydrogen has become a preferred low-carbon energy carrier. For hydrogen to truly be a clean source of energy, it must be produced from a renewable source of energy through water electrolysis. Theoretically, for each kilogram of hydrogen to be produced 9 kg of high-purity water need to be consumed, thus the enormous use of clean water for H2 production may worsen the shortage of fresh water in many parts of the world.

Owing to its abundance, seawater has received great attention in the field of hydrogen production; however, there are many challenges associated with the direct use of seawater for electrolysis. In traditional systems, the seawater is first deionized by reverse osmosis (RO) before being fed to the electrolyzer. The RO system adds complexity to the system and requires energy to be expended for the deionization. Therefore, modern systems have aimed to directly electrolyze seawater, but this comes with it own issues including electrode corrosion, scaling from the ions present in saline water, environmental concerns associated with competitive chlorine evolution reaction, and increased membrane resistance limiting the overall performance of saline water electrolysis. Several strategies have been proposed to overcome these challenges including developing selective electrocatalysts, blocking strategy, pH buffer strategy, etc.

This project sought to overcome the issues with direct seawater utilization by designing a cell that is driven by osmotic separation, but does not require an external power source. In this device, high concentration acid/base concentrations are maintained in contact with another compartment containing seawater. The acid/base reservoirs act as draw solutions, taking water passively from seawater due to their differences in osmotic pressure. This talk will focus on the cell design and operation, and include both experimental and modeling results. The rate of water transport with various cell operating configurations was quantified alongside the rate of chloride ion crossover through the anion exchange membrane. New methods for chloride mitigation were explored – including cell operating conditions, membrane design and absorption. Multiple cell configurations will be shown and strategies for reducing the cell operating voltage will be discussed.
(Invited) Comparison of Catalyst-Coated Electrodes vs. Catalyst-Coated Membranes in PEM Water Electrolysis Cells
Authors: Millet Pierre , Al Cheikh Joumada , Albacha Serge , Abdel Motagali Ali , El Rouby Waleed
Published: August 2024

The PEM (Proton-Exchange Membrane or Polymer Electrolyte Membrane) cell concept [1] is used in fuel cells and water electrolysis cells. PEM water electrolysis is a compact, efficient and flexible technology for the production of “green-hydrogen” from renewable (intermittent) energy sources. The unit cell (Figure 1) is made of several adjacent functional layers: (i) the proton-conducting polymer membrane (1); (ii) two catalysts layers (CLs) for hydrogen/oxygen evolution containing platinum group metals or PGMs (2;2’); (iii) a porous transport layer used for mass transport of reactants/products and electricity distribution (3;3’); (iv) water flow fields for water circulation (4;4’); bipolar plates (5;5’). From a practical viewpoint, the CLs can be deposited on either side of the interfaces formed between the polymer membrane and the porous transport layer: (i) on the supporting porous transport layers to form catalyst-coated electrodes which are then hot pressed against the bare membrane to form membrane – electrode assemblies; (ii) directly onto the membrane to form catalyst-coated membranes (CCM).

The aim of this paper is to evaluate the efficiency and durability of both concepts, drawing on recent advances in manufacturing techniques to reduce the loading of PGM catalysts.

[1] W.T. Grubb Jr., Batteries with Solid Ion-Exchange Electrolytes. Journal of the Electrochemical Society. 106 (1959) 275-279.

[2] C. Rozain, P. Millet, Electrochemical characterization of Polymer Electrolyte Membrane Water Electrolysis Cells, Electrochimica Acta, 131 (2014) 160-167.

Figure 1. Schematic diagram showing the cross-section of a PEM water electrolysis cell [2].

Figure 1
The Effect of PTFE Dip Coating on Enhancing the Durability and Performance of Anion Exchange Membrane Electrolyzers
Authors: Al Murisi Mohammed , Ganesan Prabhu , Mercado Hector-Colon , Mustain William Earl
Published: August 2024

Anion exchange membrane electrolyzers (AEMELs) are widely regarded as one of the most promising technologies to enable low-carbon hydrogen production. AEMELs can combine the advantages the traditional alkaline electrolyzer (AEL) and proton exchange membrane electrolyzer (PEMEL) – allowing for the use of PGM free electrodes, high operating current density, environmentally friendly materials, and compact design. Although significant progress has been made in the field of AEMELs, there is still a gap in performance compared to PEMELs that can be overcome through electrode design.

One of the most critical aspects affecting the overall performance of the AEMEC is the water management. It has a major influence on cell behavior, and specifically mass transfer at the anode side of the cell. To improve AEMEL anode water dynamics, our team modified its porous transport layer (PTLs) through the addition of controlled amounts of hydrophobic polytetrafluoroethylene (PTFE). This study investigated the effect of PTFE loading and coating method on the performance of AEMELs. Ni-based PTLs were used. Experimental results revealed that a low amount of PTFE not only enhanced the performance, but it also enhanced the catalyst layer attachment. On the other hand, higher PTFE content led to a reduction in water availability in the electrode, leading to increased mass transfer overpotentials. In summary, increasing the hydrophobicity of Ni-PTLs appears to improve AEMEC performance, with the best performing electrodes having a PTFE loading of ~1-2% (equivalent to 5-10 wt.% on carbon GDLs).
Development of Ba3TiO7-Supported IrOx Electrocatalysts for Enhanced Mass Activity in the Acidic Oxygen Evolution Reaction
Authors: Lee CHangsoo , Koo Bonjae , Lee Sechan , Kim MinJoong , Doo Gisu , Park Hyeonjung , Cho Hyunseok
Published: August 2024

Overcoming the challenge of developing highly durable and conductive support materials for Ir-based electrocatalysts in the acidic oxygen evolution reaction (OER) is difficult due to the highly corrosive conductions experienced during anodic process. In this research, we develop IrOx/Ba3TiO7 electrocatalysts, which employ Ba3TiO7 as a new support material, to minimize loading amount of iridium. We also try to fabricated Ba3TiO(7-x) support material with abundant oxygen vacancies for enhanced conductivity of the support material. As a results, the IrOx/Ba3TiO7 electrocatalysts demonstrated remarkable OER performances and enhanced mass activity compared to unsupported IrOx electrocatalysts. Through a combination of physical and chemical analyses, It was elucidated that the excellent thermodynamic stability and electrical conductivity of Ba3TiO7 effectively enhanced the mass activity of IrOx/Ba3TiO7 electrocatalysts. These finding provide further insight into new category of anode support materials for proton exchange membrane water electrolyzer.
Towards High-Performance AEM Water Electrolyzers: Transitioning from PGM to Low-PGM and PGM-Free Electrocatalysts
Authors: Amirsalehi Mahmoud , Ul Hassan Noor , Gopi K Hari , Mustain William Earl
Published: August 2024

Hydrogen, known for its high gravimetric energy density and low environmental impact, is widely regarded as a promising low-carbon energy carrier. The production of hydrogen via water electrolysis offers a valuable opportunity to efficiently utilize renewable energy resources – both as a storage and transport medium and to produce hydrogen that is a crucial feedstock for multiple industrial and manufacturing applications. Among various water electrolysis technologies, anion exchange membrane water electrolyzers (AEMWEs) are notable for their distinct and advantageous features. Their alkaline operational environment significantly reduces corrosion, allow for the possibility to use catalysts and cell component materials that are earth abundant and cost effective. Moreover, the use of anion exchange membranes (AEMs) as the electrolyte and zero-gap design enhance operational efficiency and hydrogen production rates compared to traditional alkaline electrolyzers. These benefits position AEMWEs as a compelling solution for efficient, cost-effective large-scale hydrogen production.

To date, the development of lower-cost AEMWEs has been hindered by several challenges. A critical issue is the activity and durability of catalysts, particularly those that are platinum group metal (PGM)-free. This leads many researchers and electrolyzer manufacturers to lean on PGM catalysts at both the anode and cathode. These catalysts, while effective, significantly increase the cost and complexity of the system, posing a barrier to widespread adoption and commercialization of AEMEL technology in the burgeoning hydrogen economy. PGM-free anodes have been demonstrated for the AEMWE, but there have been fewer PGM-free options for the cathode.

This study assessed the performance and durability of various low-PGM and PGM-free electrocatalysts for the oxygen evolution (OER) and hydrogen evolution (HER) reactions. We focused on Lanthanum Strontium Cobalt (LSC), Nickel Ferrite (NiFeOx), and Lead Ruthenate (PbRuOx) for the OER at the anode, and Nickel Molybdenum (NiMo), Nickel Rhenium (NiRe), and a low-PGM PtNi for the HER at the cathode. Furthermore, the performance of the NiMo HER catalyst was enhanced by optimizing the physical properties of both the catalyst powder and the electrodes. These experimental results offer crucial insights into developing PGM-free AEM water electrolyzer systems, marking a progressive step towards their commercial feasibility.
Earth-Abundant Metal Oxides as Oxygen Evolution Electrocatalysts in 1 M H2SO4
Authors: Yu Jiahao , Garcés Pineda Felipe , Galan-Mascaros Jose Ramon
Published: August 2024

Water splitting is a very hot research topic as a preferred source for green hydrogen, as a key vector to facilitate a transition into an environmentally friendly and sustainable energy economy in the mid-term. But it is still far from being economically competitive with respect to current hydrogen production technologies based on fossil fuels. One of the major economic hurdles to reduce electrolysis costs is the lack of low-cost catalysts for hydrogen evolution and, more importantly, for oxygen evolution. The water oxidation process is considered the main bottleneck in the advancement of water splitting devices, since it is the rate limiting process, and the main cause of poor long-term performance.

Most recent advances in the field of water oxidation catalysis are based on transition metal oxides, operating exclusively in alkaline electrolysis conditions. Unfortunately, these excellent oxygen evolution catalysts in basic pH ( > 13) rapidly lose their activity when the pH is lowered, and are far away from the performance exhibited by noble metals in acid solution. McCrory et al. established in 2013
1a benchmarking protocol to identify the potential of new OER electrocatalysts (and extended in 2015
2 to HER) comparing the initial activity and stability of the materials as a function of pH and showed how no other known catalysts at that time came close to the performance of IrOx-based materials.

A simple processing technique using a partially hydrophobic binder has been proved to stabilize Co oxide, resulting in electrodes able to reach high current densities (> 10 mA cm-2) at competitive overpotentials and with long term stability for acidic OER catalysis3. Following this strategy, we have been able to conduct an extensive survey of the activity and stability of monometallic, binary and ternary earth-abundant transition metal oxides during electrocatalytic OER in 1 M H2SO4. Our results confirm the general validity of the strategy in using a partially hydrophobic electrode to confer high stability to common metal oxides under these harsh conditions.

[1] C.C.L. McCrory, S. Jung, J.C. Peters, T.F. Jaramillo, Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction, J. Am. Chem. Soc. 135 (2013) 16977–16987.

[2] C.C.L. McCrory, S. Jung, I.M. Ferrer, S.M. Chatman, J.C. Peters, T.F. Jaramillo, Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices, J. Am. Chem. Soc. 137 (2015) 4347–4357.

[3] J. Yu, F.A. Garcés-Pineda, J. González-Cobos, M. Peña-Díaz, C. Rogero, S. Giménez, M.C. Spadaro, J. Arbiol, S. Barja, J.R. Galán-Mascarós, Sustainable oxygen evolution electrocatalysis in aqueous 1 M H2SO4 with earth abundant nanostructured Co3O4, Nat. Commun. 13 (2022) 4341.

Figure 1
Durability and Performance of Poly(norbornene) Anion Exchange Membrane Alkaline Electrolyzer with High Ionic Strength Anolyte
Authors: Park Habin , Li Chenyu , Kohl Paul
Published: August 2024

Anion exchange polymer electrolytes enable low-temperature alkaline water electrolysis for reliable green hydrogen production. Anion exchange membrane water electrolysis (AEMWE) with alkaline electrolytes has several advantages over the proton exchange membrane water electrolysis using acid-based polymer electrolytes. The advantages include low-cost catalysts, all hydrocarbon non-fluorinated polymer membrane, and low-cost cell components. Long-term durability of AEMWEs in high pH operation has been challenging, although there have been significant performance improvements. AEMWE operated at low hydroxide anolyte provides improved chemical stability.

In this study, an understanding of the high ionic-strength anolyte is provided along with demonstration of the AEMWE performance and durability. Anion exchange poly(norbornene) solid polymer electrolytes show high-performance, durable membrane electrode assemblies for alkaline electrolysis. Covalently bonded, self-adhesive solid polymer ionomers were used in electrodes for durable electrolysis. Hydration problem with the low pH alkaline anolyte in dry-cathode AEMWE is presented. The effect of anolyte concentration and mobile cations on the cathode electrolysis performance using a low hydroxide anolyte was investigated. High ionic strength anolyte was prepared by changing the mobile cation concentration while maintaining a constant anolyte pH. The mechanism of cathode hydration improvement through use of a high ionic strength anolyte is presented. Long-term durability with the optimal high ionic strength electrolyte is discussed.
Microwave Synthesis of New Co-Polypyrrole-Polyketone Anion Exchange Membranes
Authors: Lanero Francesco , Crivellaro Giovanni , Nale Angeloclaudio , Vezzù Keti , Di Noto Vito , Sgarbossa Paolo
Published: August 2024

Polyketones can be easily converted in a series of new polymeric anion exchange membranes (AEMs) with a stable polypyrrole-polyketone backbone structure from which the ion exchange side-groups stem [1-3]. Here we present our findings on the functionalization with two different cycloaliphatic primary amines of a commercial and inexpensive terpolymer polyketone (PK) through the Paal-Knorr chemistry. We also studied the possibility to drastically reduce the reaction time by investigating alternative and greener heating sources such as microwave heating. The molecular structure, thermal and conductive properties of the membranes were studied in order to shed light on and compare the effect of the different heating methods on the materials behavior [4], and to lead the way to their further optimization for the possible application in electrochemical devices. The obtained membranes showed a promising anion conductivity in the hydroxide form, up to 10mScm-1, and an exceptional thermal stability, about 250°C.

[1] G.Nawn, K.Vezzù, G.Cavinato, G.Pace, F.Bertasi, G.Pagot, E.Negro, V. Di Noto, Adv. Funct. Mater. 2018, 1706522

[2] N.Ataollahi, F.Girardi, E.Cappelletto, K.Vezzù, V.Di Noto, P.Scardi, E.Callone, R.Di Maggio. Journal of Applied Polymer Science. 2017, 134, 45485.

[3] A.R.Alvi, K.Vezzù, , G.Pagot, P.Sgarbossa, G.Pace, V.Di Noto, Macromolecular Chemistry & Physics. 2022, 223, 2100409.

[4] S.Bonizzoni, D.Stucchi, T.Caielli, E.Sediva, M.Mauri, P.Mustarelli, ChemElectroChem. 2023, e202201077.

Figure 1
Iridium-Based Electrocatalysts for Oxygen Evolution Reaction in Proton Exchange Membrane Water Electrolyzers
Authors: Yan Cheng , He Xiyu , Li Jing , Du Yunzhu , Yang Fan , Zhang Junliang
Published: August 2024

Proton exchange membrane water electrolyzers (PEMWEs) show the fast response to a wide electrical load range, making them compatible to couple with intermittent renewable energy systems such as wind and solar power. However, the low efficiency, instability, and high cost of anodic electrocatalysts for the oxygen evolution reaction (OER) severely hinder the widespread deployment of PEMWEs. Hitherto, iridium-based catalysts still play an irreplaceable role for their trade-off catalytic activity and stability. To meet the scarcity of iridium, reducing the iridium loading and designing low iridium-based electrocatalysts have become the mainstream. Particularly, perovskite-type oxides possess flexible compositions, enabling them ideal material platform for the optimization of catalytic performance. In this work, several materials of iridium-based perovskite-type oxides were acquired by coupling iridium with various transition elements in B-site and regulating A-site cations, which both diluted the usage of iridium and utilized the multi-metallic synergistic effect to achieve high activity and stability. Evolution of the surface structure was monitored by in-situ Raman spectroscopy to identify the active site and to uncover the catalytic mechanism. Besides, density functional theory (DFT) calculation was used as an auxiliary tool to analyze the local structure and electrochemical behavior of the electrode surface for its cost-effectiveness. Furthermore, membrane electrode assembly (MEA) based on the optimum composition was assembled to evaluate the performance of novel electrocatalysts for PEMWEs. Results of this work provide a new perspective of designing low iridium content electrocatalysts for OER in PEMWEs.

Acknowledgement

This work is funded by the National Natural Science Foundation of China (No. 22002089, 52072239).
Understanding How Porous Transport Layer Features Affect Proton Exchange Membrane Electrolyzer Performance
Authors: Hasa Bjorn , Zhu Gaohua , Aryal Utsav Raj
Published: August 2024

PEM Water electrolysis has emerged as a promising technology for the production of green hydrogen. A key component of PEM electrolyzer is the porous transport layer (PTL). The porous transport layer has numerous important roles in water electrolysis. In addition to enabling electrical conduction and water and gas transport, the PTL is necessary for maintaining excellent contact with the cell components. Cell performance is anticipated to be affected by PTL properties such as structure, composition, and thickness.

This study delves into the critical contribution of porous transport layer properties to mass transport resistance, activation losses, catalyst layer resistance, and ohmic losses. I will present our experimental framework to deconvolute the impact of PTL properties such as thickness, porosity, and microporous layer on various overpotentials. Voltage loss breakdown analysis was conducted to determine kinetic, ohmic, mass transport, and catalyst layer losses. Theoretical calculations of thermodynamic voltage typically rely on standard reaction potentials adjusted for reactant and product concentrations, operating temperature, and pressure via Nernst corrections. Ohmic voltage, which accounts for contact resistances, bulk resistances, and ohmic losses from the membrane, was determined using high-frequency impedance spectroscopy measurements. To calculate losses from OER kinetics, a Tafel fit is subsequently implemented on the HFR-free voltage. Typically, this process tends to result in residual voltage at elevated current densities, including losses arising from mass transport of water and oxygen, resistance within the catalyst layer, and impacts stemming from ionic impurities. Ionic contamination is omitted from our analysis as a result of the short duration of the experiment.

Our detailed analysis reveals that the properties of PTL can have a substantial impact on the performance of the water electrolyzer, which is crucial for enhancing the performance and durability of PEMWE. This study presents a novel framework for forecasting the performance of diverse PTL materials, which may be effectively used to drive the development and optimization of PTL for water electrolyzers.

Figure 1
Performance Optimization of Alkaline Water Electrolysis Via Catalyst Morphology Tuning and Novel Cell Design
Authors: Li Chenzhao , Stracensky Thomas , Slenker Benjamin , Gupta Ankur , Yang Zhiwei (Jv) , Xu Hui
Published: August 2024

Hydrogen is a basic energy carrier for numerous valuable industrial products. Green hydrogen produced using renewable electricity and water electrolysis is pivotal in advancing a decarbonized sustainable energy ecosystem. Two primary electrolysis technologies, alkaline water electrolysis (AWE) and polymer electrolyte membrane water electrolysis (PEMWE), have demonstrated a viable commercial perspective. AWE is particularly well-suited for large-scale deployment, especially at the gigawatt scale, due to low capital cost and long lifetime. [1]. The performance of AWE is largely determined by the effectiveness of nickel-based oxygen evolution reaction (OER) catalysts and PGM-based or PGM-free hydrogen evolution reaction (HER) catalysts. To enhance the catalyst activity and cell performance, we meticulously control morphology and chemical composition of the catalysts. Cell testing was conducted in cells of various active areas (5, 25, and 50cm2) to demonstrate the result consistency and scalability. An innovative cell design, incorporating a reference hydrogen electrode in both cathode and anode, enabled the real-time acquisition of half-cell polarization curves during tests. This configuration proved valuable information to identify performance limitations in the single cells, thus guiding effective cell design and optimization. Furthermore, a cell comprising Ni-based anode and PGM cathode demonstrated remarkable stability.

1. Schalenbach, Aleksandar R. Zeradjanin, Olga Kasian, Serhiy Cherevko, and Karl J.J. Mayrhofer, Int. J. Electrochem. Sci., 1173–1226 (2018).
Morphological and Surface Electronic Structure Design of Alloys Electrocatalyst for Alkaline HER
Authors: Hsu Chia-Chi , Nguyen Thi Xuyen , Ting Jyh-Ming
Published: August 2024

Among the various hydrogen production methods, water electrolysis provides numerous advantages, including high purity of the produced hydrogen and low carbon emission. In this context, one of the concerns is associated with the replacement, or partial replacement, of noble-metal electrocatalyst for hydrogen evolution reaction (HER) by low-cost, commercially viable ones. To achieve this objective, alloying provides a direct way to tailor the electronic structure of active site and hence is expected to effectively reduce the usage of noble metal. Furthermore, increasing the surface area through morphology design is considered a promising method for enhancing catalyst activity. Among the diverse strategies to increase the surface area, dealloying plays a unique role by generating porous structure, thereby offering advantages in terms of cost-effectiveness and controllable structure. In this study, we have synthesized various Zn-Ni based alloy electrocatalysts using a facile solvothermal method, followed by a dealloying process. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry are used to examine the morphology, composition, and electronic structure. The electrochemical performance is investigated using linear sweep voltammetry, electrochemical impedance spectroscopy, cyclic voltammetry, and electrochemical specific surface area analyses. We demonstrate that resulting HER alloy electrocatalyst exhibits a low overpotential and Tafel slope, and good stability over 200 hours.
Transition Metal Oxide/Sulfide on the Ni Foam for Electrocatalytic UOR & OER
Authors: Liu Chih-Yu , Nguyen Thi Xuyen , Ting Jyh-Ming
Published: August 2024

Water electrolysis is an important technology related to the energy conservation, is a promising technology. Currently, one of the key efforts is to improve the efficiency and reduce the cost of water electrolysis, in particular, the anodic oxygen evolution reaction (OER). Nobel-metal free OER catalyst or alternative urea oxidation reaction (UOR) is thus favored. Due to the advantages of enhance charge transfer and desirable charge redistribution, we have investigated nobel-metal free transition metal oxide/sulfide heterostructure UOR electrocatalyst. Co-Ni based metal heterostructure is synthesized using a simple two-step hydrothermal method. The resulting samples are examined using X-ray diffractometer, Scanning electron microscopy, X-ray photoelectron spectroscopy and the Inductively coupled plasma will used as the material analysis. Electrochemical performance is evaluated using linear sweep voltammetry, electrochemical impedance spectroscopy, cyclic voltammetry, and electrochemical active surface area. Moreover, the electrocatalyst is also evaluated as OER catalysts. The relation between the material characteristics and the electrochemical performance is discussed.
Exploring the Phase Transformation of Tri-Metallic Prussian Blue Analogue Pre-Catalyst for Improved Oxygen Evolution Reaction
Authors: Nguyen Thi Xuyen , Yang Kai-Hsiang , Su Yen-Hsun , Ting Jyh-Ming
Published: August 2024

The development of non-noble metal electrocatalyst with high-efficiency and clear underlying of the related reaction mechanism towards the sluggish oxygen evolution reaction (OER) is critical for large-scale hydrogen production. In this study, tri-metallic Prussian blue analogue (PBA) of FeCoNi-PBA was synthesized using a facile and low-energy consumption co-precipitation method. The FeCoNi-PBA was found to be etched by the high-pH 1 M KOH electrolyte such that under anodic applied potential during electrolysis the formation of metal (oxy)hydroxide is accelerated. Operando Raman and post-mortem characterizations reveal that the applied anodic potential promotes the phase transformation so that the PBA undergoes self-reconstruction to form metal (oxy)hydroxide embedded in a carbon matrix with fully exposed active sites. The metal (oxy)hydroxide serves as the real active sites while the carbon matrix is believed to enhance the conductivity and hydrophilicity, which facilitates the electron transfer and electrolyte diffusion to improve the OER performance. In alkaline media, FeCoNi-PBA demonstrates excellent OER performance with a low overpotential of 236 mV at 10 mA cm−2, small Tafel slope of 43.8 mV dec-1, and long-term durability.
Surface Decorated SnOx modifiers Boost Oxygen Reduction and Hydrogen Evolution Reaction Performance of Pt Nanorods
Authors: Liu Pin Yu , Chen Tsan-Yao , Bhalothia Dinesh , Chen Pochun
Published: August 2024

The development of efficient, durable and commercially competitive catalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is undoubtedly a challenging task for fuel cell technology. In this context, for the first time, we developed a bi-metallic heterogeneous nanocatalyst (NC) comprising high-density atomic SnOx-clusters anchored Pt-nanorods (denoted as SnOx@Pt) via formic acid reduction method (FAM) as a bifunctional catalyst for ORR and HER (Fig.1). The as-prepared SnOx@Pt nanorods exhibit unprecedented high mass activity (MA) of 160 mAmg-1 (Pt) at 0.85 V vs RHE in acidic ORR (0.5M HClO4), which outperformed the commercial J.M.-Pt/C (20 wt.% Pt) catalyst by 1.4 folds. Of special relevance, SnOx@Pt nanorods exhibit remarkable durability when operated up to 5000 cycles in accelerated durability test (ADT) and retain their 87% MA as that of the initial condition. Additionally, as-prepared SnOx@Pt nanorods demonstrated a notable lower overpotential (η) of 48 mV at the cathodic current density of 10 mAcm-2 and the Tafel slope of 33 mVdec -1 in acidic HER (0.5M H2SO4). These overpotential and Tafel slope values are significantly lower compared to commercial J.M.-Pt/C catalyst (η = 60 mV and Tafel slope = 38 mVdec-1). Moreover, such material retained its 100% performance in the chronoamperometric (CA) stability test up to 6h, which shows its capability in potential commercialization. The cross-referencing results of physical inspections and electrochemical analysis reveal that such a high-performance of SnOx@Pt nanorods is attributed to the local synergetic collaboration between SnOx modifiers and neighboring Pt active sites. More specifically, the SnOx modifiers promote the H-OH bond cleavage during HER, while simultaneously promotes the desorption of oxygen species on Pt surface in ORR, which later triggers the reduction reaction performances. Meanwhile, SnOx provides a shielding effect to Pt during harsh reduction conditions and thus high stability of SnOx@Pt nanorods is achieved. Of utmost importance, this study not only unveils a novel geometric design but also provides the mechanistic understanding behind the superior electrochemical properties of the unique SnOx modifiers in ORR and HER. Hence, we envision that the proposed rationale will be a forwarding step for the development of high-performance low Pt content catalysts for fuel cells with superior electrochemical properties far beyond the physical nature of transition elements.

Keywords: Oxygen reduction reaction, hydrogen evolution reaction, fuel cells, nanocatalysts, mass activity
Probing the Catalyst-Ionomer Interface during Electrochemical CO2 Reduction
Authors: Chen Zhu , Jain Pulkit , Tran Nhan Huu Huy , Fuentecilla Shane
Published: August 2024

The catalyst-ionomer interface can significantly impact the selectivity of the electrochemical CO2 reduction (CO2R) reaction. Ionomers such as Nafion are commonly used in conjunction with nanostructured CO2R catalysts in flow cells and zero-gap devices, with their presumed function being to act as a binder for the catalyst. However, recent studies have reported that ionomers such as Nafion and Sustainion can affect the reaction rate and selectivity of CO2R, and the roles of ionomer in controlling mass transfer and local pH have been hypothesized. We employed in situ Raman spectroscopy to examine CO2R intermediate and local pH on a sputtered copper (sCu) surface with and without an ionomer overlayer. We observed a difference in the potential-dependent formation of surface CO in the presence of Nafion compared to clean sCu. Using a combination of pH-sensitive probe molecules, we also determined the pH at the catalyst-ionomer interface.
(Invited) Plasmonic and Electrochemical Approaches to the Synthesis of Tailored Catalyst Materials
Authors: Personick Michelle L.
Published: August 2024

The development of novel photo- and electrocatalytic processes requires the design of catalyst materials that are specifically optimized to take advantage of these driving forces. This talk will describe approaches developed in our lab for (1) using visible light stimulus to control the structure of plasmonically responsive and hybrid materials and (2) using electrodeposition to grow shape-controlled nanostructures on electrode surfaces. In the first case, the reduction of more catalytically active metals onto plasmonically active metals requires fine control over competing reductive and oxidative chemical processes. Differentially modulating the rates of these reactions using only chemical and thermal parameters can be prohibitively challenging. However, excitation of the plasmon resonance of the growing nanoparticles using visible light can yield hybrid structures that are not accessible via standard colloidal approaches. In the second case, while particles synthesized in colloidal solution can be processed and cast onto electrodes, this adds an additional fabrication step—increasing time and cost—and faces challenges in controlling particle dispersion on the surface. Meanwhile, direct chemical reduction-based synthesis of well-defined nanoparticles on electrodes has proven difficult. We have developed an integrated electrochemical approach that enables directed synthesis of shaped nanoparticles on electrode surfaces. Our approach links metal nanoparticle synthesis with real-time monitoring of chemical changes in the reaction solution using a combination of colloidal particle synthesis, electrochemical particle synthesis, and electrochemical measurements. This provides a pathway for the directed adaptation of the extensive library of existing shaped colloidal nanoparticle syntheses to growth on a surface—something that remains a non-trivial challenge.
(Invited) Probing Spin Selective Surface Chemistry with Circularly Polarized XUV Light
Authors: Baker L. Robert , Gajapathy Harshad , Schutlze Martin
Published: August 2024

Controlling spin states of surface reaction intermediates is an important but often overlooked parameter to designing semiconductor photocatalysts to mimic nature’s best photosynthetic complexes. Extreme Ultraviolet Reflection-Absorption (XUV-RA) spectroscopy enables direct observation of surface electron dynamics by combining element, oxidation, and spin state resolution, with surface sensitivity and ultrafast time resolution. While absorption of linearly polarized XUV light can probe the local oxidation and spin states of individual elements, it is insensitive to absolute spin alignment. To enable the study of spin-selective electron dynamics at interfaces, we have recently implemented ultrafast XUV Magnetic Circular Dichroism (XUV-MCD). Employing XUV-MCD in a reflection geometry, we are now studying the ultrafast surface electron dynamics that give rise to spin polarized photocurrents in magnetic and chiral semiconductors. As an example, yttrium iron garnet (Y3Fe5O12, YIG) is a ferrimagnetic oxide with a visible band gap, consisting of two sub-lattices based on octahedrally and tetrahedrally coordinated Fe(III) centers. Ultrafast XUV measurements show that electron-phonon coupling and polaron formation rates differ significantly between octahedral and tetrahedral centers leading to very different charge carrier recombination kinetics. Circular measurements show that this difference in recombination rate gives rise to long-lived, spin-polarized charge accumulation at the YIG surface that drives spin selective water oxidation. This new ability to observe real-time spin polarization at surfaces promises to provide key design parameters for semiconductor photocatalysts capable of spin selective surface chemistry.
(Invited) How to Mitigate Excited State Polaron Formation in Transition Metal Oxide Photocatalysts
Authors: Cushing Scott K
Published: August 2024

We measure how lattice versus electronic coupling in transition metal oxide photocatalysts can mitigate photoexcited polaron formation. Despite well-aligned energetics for photocatalysis, transition metal oxide materials have limited carrier mobilities due to the formation of polarons. The coupling of photoexcited charge carriers with phonons in the crystal lattice causes carrier localization and results in transport that relies on site-to-site hopping. Models that predict polaron formation are limited to ground-state predictions, which limits the exploration of new photocatalysts. Small polaron formation rates have been measured to be independent of defects, dopants, surface treatments, and other material tuning parameters. Our transient extreme ultraviolet (XUV) measurements show the first hints about how electronic correlations can be used to counter polaron formation for increased transport. For example, in CuFeO2, we add Cu layers between FeO6 octahedra, which increases photoexcited transport compared to α-Fe2O3. In ErFeO3, where Er frustrates FeO6 octahedra, coherent Fe-Fe charge hopping due to correlated electron interactions slows polaron formation. We frame our discussion in terms of the Hubbard-Holstein Hamiltonian, which we are slowly proving can be used to guide materials design rules for non-polaronic photocatalysts using only ground-state DFT parameters.
Semi-Analytical Model for Hybrid and Redox Targeting Flow Battery Systems
Authors: Bao Jie , Chen Yunxiang , Gao Peiyuan , Saldanha Emily , Howard Amanda , Wang Wei , Sprenkle Vincent
Published: August 2024

Redox flow battery represents an economically viable energy storage technology that can integrate intermittent renewable energies from solar and wind power into existing electric grids. Besides the conventional all-liquid redox flow battery, there are two different architectures of flow batteries: hybrid and redox targeting flow batteries. Because the reactive solid phase is involved in the system, the energy storage density increases significantly. Therefore, they are considered as ones of the potential solutions for the future large-scale deployment of long-duration energy storage systems (LDES). A digital twin (DT) has been demonstrated as a promising numerical framework and platform to assist in the design, deployment, and operation of LDES. DTs usually require a fast-response model to provide an estimation of the flow battery's performance, which can be a fast-forward physics-based model or a machine learning-based regression model. Many pioneering works and our previous studies have introduced several fast-forward physics-based models for the conventional all-liquid redox flow battery in both inorganic and organic systems. In this study, a semi-analytical model, which can adapt to DTs, is proposed to provide an estimation of the performance of the hybrid and the redox targeting flow battery at different operating conditions.