bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation on Two-Phase Flow-Electrochemical Reaction Coupling in PEM Water Electrolyzers Porous Transport Layer Under High Operating Pressures
Authors: Yang Qiu , Zhang Ruiming , Sui Pang-Chieh
Published: August 2024

Proton exchange membrane water electrolyzers (PEMWEs) operated at high pressures have advantages such as lower energy consumption, reduced noise, and absence of component slippage. They have a more robust potential for commercial applications than other electrolyzers. The transport characteristics of two-phase flow within the porous transport layer (PTL) and channels are not well understood, especially under high-pressure conditions. The gas bubbles generated in the catalyst layer (CL) pass through the PTL and reach the flow channel. However, oxygen evolution reaction in the anode CL may be limited if these bubbles block the pathway of liquid water, causing reactant starvation. The interaction between electrochemical reactions and gas bubbles thus directly impacts a PEMWE's efficiency. This study aims to investigate the coupling between the two-phase flow and electrochemical reactions under high-pressure conditions.

A two-dimensional (2D) CFD model was developed to simulate the bubbly flow through a reconstructed PTL. The volume of fluid (VOF) method was employed to capture bubble growth, movement, and detachment, as illustrated in Figure 1. The coupling of bubble transport and electrochemical reactions was achieved through the application of a weighted averaging method. A cross-section of a stochastically reconstructed titanium felt model was generated as the computational domain; see Fig. 1(a). The computation domain consists of a liquid water channel, a PTL, and a simplified CL interface at the bottom. The CL's reaction rate is modeled as a function of local bubble coverage on the CL interface. Transient simulations of the two-phase flow of the PEMWE anode side were carried out for pressures ranging from 1 bar to 200 bar. The simulation results elucidate the flow characteristics of liquid water in the PTL under high-pressure conditions and quantitatively reveal the coupling between two-phase flow and electrochemical reactions. The behavior of the two-phase flow in PEMWE is found to be sensitive to operating pressure. As the operating pressure increases, the size of bubbles generated on the CL interface decreases, resulting in a higher permeability of liquid water than that under low pressures. When the flow rate of liquid water in the channel is sufficiently high, bubbles do not fully develop and are rapidly removed from the domain. This phenomenon significantly shifts the two-phase flow regime within the channels,. Furthermore, the activation overpotential is substantially reduced under high-pressure conditions. The present study demonstrates a numerical simulation tool for high-pressure PEMWE. A future study of a full 3D PTL model is currently underway.

Figure 1
(Invited) On the Importance of the Catalyst- and Porous Transport Layer Interface on Pewe Performance
Authors: Buechi Felix N. , Weber Carl Cesar , Schuler Tobias , Wrubel Jacob A , Bender Guido
Published: August 2024

The need to develop polymer electrolyte water electrolyzers with minimum amounts of precious materials, in particular those from the platinum metal group, but conserving high performance needs development and optimization of many materials and components.

The interface between the catalyst- and porous transport layers (PTL) is in this respect particularly important as it seems to have a strong influence on the current density distribution, the IrO2 catalyst utilization and it’s mass activity. All of these parameters should be optimized.

The presentation reviews the effects of PTL structures on the decisive limitations, explains improvements and tries to make a look into the future.
Benchmark and Roadmap for Low Temperature Water Electrolysis for Green H2 Production and Applications
Authors: Xu Hui
Published: August 2024

Water electrolysis has attracted world-wide attention due to its ability to produce green hydrogen when coupled with renewable electricity. Green hydrogen is a viable solution to decarbonizing a variety of industries including fertilizer, metal production, petrochemical, and synthetic fuels. There are three major low temperature water electrolysis technologies, alkaline water electrolyzer (AWE), proton exchange membrane water electrolyzer (PEMWE), and anion exchange membrane water electrolyzer (AEMWE). This work will first provide the status of these three technologies in terms of operating conditions, lifetime, and capital cost. Subsequently, the challenges and constraints for these technologies will be discussed in the scenarios of large-scale manufacturing and integration with intermittent renewables. More efforts will be made to illustrate the trajectory of the next-gen water electrolysis technologies, which feature at ultralow PGM or PGM-free catalysts, thin membranes with reduced hydrogen crossover, high-current high-power operation, long lifetime, and remarkable cost reduction. The work will also address the challenges of automated MEA fabrication and stack manufacturing at scale. Finally, a real example of renewable wind turbine integrated with water electrolyzer to produce green hydrogen and subsequently green ammonia will be demonstrated.
Understanding in-Plane Movement of Iridium in Proton Exchange Membrane Electrolyzer after Accelerated Stress Test
Authors: Ebrahimpour tolouei Nadia , Chabot Florian , Zhu Gaohua , Zenyuk Iryna
Published: August 2024

In the rapidly evolving field of clean energy, proton exchange membrane water electrolyzers (PEMWEs) stand at the forefront, heralding a new era of sustainable hydrogen fuel production. PEMWEs need to operate for at least 10 years and material degradation is a challenge that needs to be overcome. Here we use H2NEW accelerated stress (AST) protocol to degrade 5 cm2 PEMWE cell having low iridium loadings on the anode side. Using X-ray fluorescence (XRF) mapping, we first assessed the iridium distribution at the beginning of life (BOL) of the electrolyzer cell and then afterwards at the end of life (EOL). Regular electrical characterization with specific time intervals was conducted, such as collection of polarization curves, electrochemical impedance spectroscopy and cyclic voltammetry. Identical location was selected for iridium mapping. To complement XRF mapping, we also conducted X-ray diffraction (XRD) studies at the BOL and at the EOL. XRD reveals the crystalline structure and phase transitions of iridium, crucial for understanding how iridium’s atomic arrangement adapts to operational stresses. This comprehensive approach, combining XRF and XRD, aims to provide a multifaceted view of iridium’s behavior, distribution, and structural changes from the BOL to EOL. This research aims to unravel the behavior of iridium after AST, particularly whether it migrates into the ionomer, moves to the cathode, or undergoes other transformational shifts.

Figure 1.micro-XRF map of iridium distribution on the anode of the PEMWE at the BOL. The map is 2 mm x 2 mm.

Figure 1
Insights into Ir-Based Trimetallic Nano-Catalyst for Acidic Water Electrolysis
Authors: Tesfaye Robel Mehari , Chuang Po-Ya Abel , Karmakar Ayon
Published: August 2024

In the pursuit of a sustainable and environmentally friendly energy future, water electrolyzers emerge as indispensable players in the landscape of renewable energy storage. At the core of their significance lies the ability to convert surplus renewable energy, such as solar or wind power, into hydrogen - a clean and versatile energy carrier. Through the process of electrolysis, water molecules are split into hydrogen (via Hydrogen evolution reaction, HER) and oxygen (via Oxygen evolution reaction, OER) using electricity, typically derived from renewable sources. However, current hydrogen production is still heavily relying on fossil fuels, with natural gas reforming as the primary source. Despite its high cost, iridium oxide (IrO2) is the most commonly used catalyst for the sluggish OER. Combining Ir with other non-noble metals is one strategy to reduce Ir loading, while maintaining and even increasing catalyst activity. Bimetallic alloying of Iridium-based nanomaterials has the potential to enhance its intrinsic catalytic properties towards acidic OER than that of the single element doped catalyst. The mechanisms include providing more reaction active sites, tuning the electronic structure of the matrix, and synergistic effects that promote the catalytic reaction by facilitating the formation and stabilization of active oxygen intermediates. Although many transition metals, such as Ni, Co, Fe, Mn, W, Sn, Nb, and Ti, have been doped into Ir to from bimetallic and trimetallic catalyst structures, no studies have explored the fundamental relationship between dopant and catalyst activity. This work systematically investigates the effect of doping Iridium-Cobalt matrix with a third, fourth-period transition metals including Mn, Cr, Fe, Co, Ni and Cu, towards acidic OER activity. A facile one pot chemical reduction synthesis is used to synthesize the trimetallic nanomaterials. Half-cell measurements are conducted to evaluate the electrochemical performance and stability of the catalysts. Lastly, physio-chemical methods are used to characterize the composition and structure of the catalysts. At the ECS meeting, we will share our results to provide new insight into structure-function relationships of our bimetallic-doped Ir catalysts.
(Invited) Understanding the Effect of Cell Assembly and Operation on AEM Electrolyzer Performance and Durability
Authors: Amirsalehi Mahmoud , Gopi K Hari , Mustain William Earl
Published: August 2024

Water electrolysis to produce hydrogen is gaining significant attention due to a significant decrease in the cost of renewable energy sources such as solar, wind, and tidal etc. Among the existing water electrolysis technologies, anion exchange membrane water electrolysis has recently emerged due to its potential advantages over proton exchange membrane electrolysis and traditional alkaline electrolysis. Anion exchange membrane electrolyzers (AEMELs) can allow for the use of PGM-free electrocatalysts and low-cost component materials due to its less corrosive alkaline environment while also enabling electrochemical H2 compression.

An overwhelming majority of the research that is going on related to AEMELs is the synthesis of advanced functional nanomaterials – e.g. new catalysts and membranes. Though these are critically important components of the cell, their function is supported by a multitude of other factors. For example, it is well-known that water and gas transport in the electrodes is highly dictated by the porous transport layers. The electrode fabrication technique controls the electrode morphology. The synthesis method for the catalyst determines its porosity and structure. The cell gasketing controls compression. The operating current density and temperature affect stress at the material and electrode level, and dictate other properties such as exchange current, ionic conductivity, water uptake, diffusivities, etc. Many of these properties are less reported and will be the subject of this presentation.

This presentation will focus on understanding how various decisions that are made regarding electrode fabrication, cell assembly and cell operation affect the operating voltage and voltage stability of AEM electrolyzers. The goal of this talk is to combine electrochemical and physical characterization data to develop a series of guiding principles for AEMEL operation that can be used across polymer chemistries and catalyst selection.
Interface Engineering of Transition Metal-Based Heterostructure Electrocatalysts for Enhanced Hydrogen Evolution Reaction
Authors: He Rong , Luo Hongmei , Zhou Meng
Published: August 2024

Electrochemical water splitting to produce clean hydrogen plays a significant role in the development of the hydrogen economy. The rational design of highly efficient and inexpensive electrocatalysts is critical for improving water electrolysis efficiency. Herein, we report the fabrication of heterostructure monometallic, bimetallic, and trimetallic sulfides on Ni foam (NF) as porous self-supported electrodes for hydrogen evolution reaction (HER) via an energy-saving electrodeposition process. Molybdenum-cobalt-nickel sulfide electrode (MoCoNiS@NF) only requires a low overpotential of 114 mV to produce a current density of 10 mA cm-2 for HER, compared with nickel sulfides (NiS@NF, 142 mV) and cobalt-nickel sulfides (CoNiS@NF, 129 mV). The desirable HER performance of MoCoNiS@NF results from the synergistic effect of heterostructure interfaces of multi-metal sulfides, providing high intrinsic catalytic activity and a large amount of catalytic active sites. Electrochemical impedance spectroscopy and Tafel slope analysis proved the fast reaction kinetics of MoCoNiS@NF toward HER. Our present work provides valuable insights into the working mechanisms behind the HER catalytic process and new perspectives for the future design of cost-effective electrocatalysts for HER.
(Invited) A Hybrid Electrochemical and Catalytic Compression System for Direct Generation of High-Pressure Hydrogen at 350 Atmospheric Pressure
Authors: Xiang Chengxiang("CX")
Published: August 2024

Hydrogen is becoming the center piece in the global de-carbonatization efforts in multiple industrial sectors. Gaseous hydrogen at high pressures in gas tanks is the most common approach for H2 storage, transportation and hydrogen refueling for fuel cell vehicles. Gaseous hydrogen at high pressures is also heavily used in the Haber process for ammonia production and hydro-cracking of heavy petroleum. In the long term, low-cost high pressure H2 will also play a critical role in the future long-duration grid storage for deep decarbonization and improved resilience.

In this talk, I will share some recent development on a hybrid electrochemical/catalytic approach for direct generation of high-pressure H2 in collaboration with Pacific Northwest National Laboratory (PNNL). The hybrid system oxidizes water to oxygen at the anode, reduces V3+ to V2+ at the cathode, and stores proton in the catholyte during the “electrochemical charging” step. We demonstrated that the charged catholyte is then capable of generating H2 at >350 bar in the subsequent “catalytic discharging” step without any additional energy input. This concept leverages the electrochemical Nernst potential difference between the redox couple (V2+/3+) and the hydrogen evolution reaction and delivers a unique system that is capable of generating H2 at demand and at high pressure without any mechanical or electrochemical compression. We estimate a cost of <$0.19/kg-H2 for compression, representing >80% of the cost reduction compared to the traditional multi-stage compressor approach.
(Invited) Selective Glucose Conversion into Gluconic Acid By Dye-Sensitized Photoelectrochemical Cell
Authors: Qamar Muhammad Zain , Kang Hyeong Cheol , Asiam Francis , Sadiq Muhammad , Lee Jae-Joon
Published: August 2024

Gluconic acid, one of the valuable products of oxidized glucose projected to soon hit a market value of US$1.9 billion is currently produced using relatively expensive electrochemical, environmentally unsafe chemical or thermal selective oxidation methods to meet market demand. Dye-sensitized photoelectrochemical cells (DSPECs) which has effectively been utilized for selective biomass conversion into other valuable products (alongside hydrogen evolution) is a cheaper, greener and safer alternative unexplored in this field. Herein, we explore this green technology for selective oxidation of glucose into gluconic acid in an aqueous system, employing metal-free organic dye (E)-3-(5-(4-(bis(2',4'-dibutoxy-[1,1'-biphenyl]-4-yl) amino) phenyl) thiophen-2-yl)-2-cyanoacrylic acid (D35) with organic catalyst (4-Acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl) ACT at 0 V vs NHE. Photophysical details revealed the occurrence of intermolecular electron transfer between D35 and ACT under 1 sun illumination (100 mW/cm²). Enhanced generation of the strongly oxidizing reactive oxoammonium species, ACT+, by the photoanode drives the conversion of glucose into gluconic acid. The photoanode assembly employed exhibited remarkable stability, sustaining a continuous operation for 3 days and 88% selectivity for gluconic acid at pH 7. The aqueous phase stability, selectivity, neutral environment and ambient operation of the setup indicates it potential for biomass conversion and hydrogen production towards commercialization purposes.
Application of Fe3O4@MoS2 & Co@MoS2 for Electrocatalytic Nitrogen Reduction Reaction Under the Magnetic Field
Authors: Wang Shao-Che , Wang Shao-Che , Ho Chia-Chen , Li Shao-Sian
Published: August 2024

Ammonia, one of the most essential raw ingredient for fertilizers, pharmaceuticals and neutralization. However, the widespread production of ammonia heavily depends on the Haber-Bosch process, which entails substantial use of fossil fuels due to the demanding reaction conditions involving high pressure and temperature. Consequently, finding a sustainable method for synthesizing ammonia becomes crucial in addressing environmental pollution and mitigating energy crises.

In order to improve the efficiency of ammonia production, using materials with high catalytic activity is an important factor. Traditional noble metals are recognized as the best catalytic materials. Nevertheless, the high cost and rarity of noble metals make their development and application has haven limited a lot. In recent years, two-dimensional materials attracted the attention of scientists in the field of catalysis. Among them, Molybdenum disulfide has a unique crystal structure and properties. Therefore, we aim to create a heterostructure by doping Co or incorporating Fe3O4 into MoS2, resulting in a material with either paramagnetic or ferromagnetic properties. We intend to observe the electrochemical performance of these materials under an applied magnetic field to further substantiate the influence of the magnetic field on electrocatalytic performance.

Eventually, we successfully improved the performance of Nitrogen Reduction Reaction under the magnetic field. In the test of electrochemical performance at -0.04V (vs. RHE), we successfully increased the Faradaic efficiency of Fe3O4@1T-MoS2 from 32.67 to 37.16. Simultaneously, we elevated the Faradaic efficiency of Co@1T-MoS2 from 22% to 35%. From the result, we further confirmed that with the adding of magnetic field our catalyst can reach a better NRR performance.

key word: nitrogen reduction reaction, Fe3O4@1T-MoS2, Cobalt-doped 1T phase molybdenum disulfide, magnetic field
(Invited) Evolution of Single Atom Catalysts during CO2 Electrocatalytic Reduction
Authors: Roldan Cuenya Beatriz
Published: August 2024

The re-utilization of CO2 via its electrocatalytic reduction (CO2RR) into value-added chemicals and fuels is a promising avenue to minimize the impact of existing technologies on the climate change. This requires the development of low cost, efficient, selective and durable electrocatalysts based of their rational understanding. Moreover, it should be considered that even morphologically and chemically well-defined pre-catalysts can be susceptible to drastic modifications under operation, especially when the reaction conditions themselves change dynamically.

This talk will address the transformations that Metal-N-C catalysts (M=Cu, Ni, Co, Fe, Sn, Zn) experience during static and pulsed CO2RR using operando quick X-ray absorption spectroscopy (XAS) and Raman spectroscopy. In particular, I will illustrate the astonishing behaviordisplayed by Cu-N-C catalystsduring CO2RR, featuring reversible transformations from single atom sites towards Cu nanoparticles. The switchable nature of these species that can be achieved by applying different potential pulses holds the key for the on-demand control of the distribution of the CO2RR products and thus, a wide-spread adoption of this process.

Moreover, I will elucidate the nature of the ligands forming under CO2RR at singly dispersed Ni sites in Ni-N-C catalysts, which are currently drawing great attention for their high performances in the CO formation. This will be achieved by a synergistic combination of conventional XAS, high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) spectroscopy, and X-ray emission spectroscopy (XES) coupled with unsupervised and supervised machine learning methodologies and density functional theory.

Overall, my lecture will feature the importance of operando characterization of electrocatalysts in order to unveil structure/composition-reactivity correlations during CO2RR.
(Invited) Upconverted Hot Electrons from Semiconductor Nanocrystals for Enhancing Photocatalysis
Authors: Son Dong Hee
Published: August 2024

The exciton-to-hot electron upconversion phenomenon in Mn-doped semiconductor quantum dots (QDs) produces highly energetic hot electrons. These electrons have an average energy just a fraction of 1 eV below the vacuum level, with a subpopulation of hot electrons existing above the vacuum level. This hot electron upconversion process is similar to photon upconversion in lanthanide-doped nanoparticles. However, the final state here is a highly excited hot electron in the conduction band of the host QDs, not a state emitting higher-energy photons. These upconverted hot electrons can be harnessed to carry out thermodynamically and kinetically challenging reduction reactions, benefiting from their high excess kinetic energy and long-range transfer capability. The presentation will discuss recent demonstrations of the benefits of these upconverted hot electrons in various photocatalytic reduction and redox-neutral reactions. Additionally, the development of new materials for more efficient hot electron upconversion and the potential to broaden the application of these energetic hot electrons beyond photocatalysis will be discussed.
Development of Organic Positive Electrodes for Rechargeable Aqueous Zinc-Ion Batteries for Stationary Energy Storage Systems
Authors: Ibarra Espinoza Alejandra , Baker Thomas James , Sanders Kevin J. , Gourley Storm William D , Liu Zeyuan , Adams Brian D , Goward Gillian R. , Higgins Drew
Published: August 2024

The rising concern towards the amount of anthropogenic carbon emissions and their effects on the environment has motivated the transition away from fossil fuels. The implementation of renewable energy sources has promoted the decarbonization of the power sector, but the variability of wind and solar energy necessitates the parallel deployment of high-performance energy storage infrastructure to ensure a reliable on-demand supply of green electricity to the grid. To this end, aqueous rechargeable zinc-ion batteries (ZIBs) are a promising new option for stationary energy storage owing to their high safety and low cost, when compared to established storage technologies like lithium-ion batteries. However, ZIBs are still limited by several technological challenges that hinder their uptake for commercial energy storage installations. In particular, the positive electrode materials, mostly comprised of metal oxides, are restraining the energy density and stability of the batteries and are yet under investigation. Low cost, long cycle life, and natural abundance are required properties of materials used in batteries for stationary energy storage. The search for materials with these properties has motivated the investigation of alternatives to metal oxides. One group of materials attracting considerable research attention is organic compounds which offer advantages like their natural abundance and high theoretical capacities. In this work, we developed an organic positive electrode for ZIBs using carbonyl groups as redox-active centers to provide energy storage capacity at round-trip energy efficiencies that are higher than the conventionally utilized manganese oxide electrodes. Furthermore, we investigated the effects of the conductive carbon additive on the deliverable capacity of the battery and elucidated the charge storage mechanism of this positive electrode material through detailed characterization. The results indicated that both Zn2+ and H+ are involved in the energy storage process of this organic electrode material. In addition to studying the energy storage process, degradation mechanisms were identified through nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Both dissolution of the reduced form of the active material from the electrode and the formation of unwanted decomposition products are important contributors to the capacity fade of the battery. The technological and scientific insights provided in this presentation will thereby contribute towards the development of high-performance and naturally abundant electrode materials for the next generation of ZIBs to enable clean energy grid storage.
(Energy Technology Division Research Award) New Materials vs. Reaction Engineering in Anion Exchange Membrane Fuel Cells
Authors: Mustain William Earl
Published: August 2024

In recent years, the desire to design, create and/or discover advanced functional nanomaterials has changed the way that faculty members and graduate students approach engineering research. Though materials can (and likely will) make a significant impact on most technologies, the truth is that in most disciplines, materials with highly complex structures remain on the fringes of realistic deployment. In some cases, even when so-called “advanced” materials are discovered there are significant difficulties in transitioning them from ex-situ tests to the real reacting environment. Therefore, we must be careful to understand that material chemistry and structure are only two variables in an extremely complex system and often times there are other fundamental (e.g. electronic mobility, thermodynamic barriers, diffusivity) and engineering (porosity, concentration, temperature) properties that drive behavior in such environments. Additionally, there are systems where materials are being sought without a clear understanding of what is truly limiting performance and durability or the properties that are required of a real engineered system to operate effectively.

Anion exchange membrane fuel cells (AEMFCs) are an example system where the literature is littered with exotic materials that claim to improve activity and stability (presumed as performance and durability in real devices). However, it will be shown that for several years, such new materials had limited success (if any) in advancing performance and durability. This talk will summarize ~five years of work in AEMFCs where the performance and durability of AEMFCs were improved significantly without any new materials – just using traditional chemical engineering principles for reactor engineering. Only later – once device operation was well understood and controlled – were new materials helpful. On the operational side, the main discussion point will be the transport of water. On the materials side, new membranes and catalysts will be discussed. The talk will end with perspectives on transitioning AEMFCs to more realistic operating environments, including the mitigation of effects from CO2.
Electrospun Nanofiber Catalyst Support for Polymer Electrolyte Membrane Fuel Cells
Authors: Pedram Sara , Wang Yinyu , Jankovic Jasna
Published: August 2024

Increased energy demand and environmental concerns are driving the search for cleaner, more efficient power generation. Fuel cells (FCs) offer a solution by converting chemical energy from fuel and oxidant directly into electricity with high efficiency (40-70%) and zero carbon emissions. Enhancing the performance and durability of polymer electrolyte membrane fuel cells (PEMFC) while reducing costs remains a significant challenge. The current planar FC design presents various issues, including high costs and weight due to metal or graphite bipolar plates, high-pressure drop-in reactant gas diffusion channels, reactant gas transport losses in the agglomerate-type catalyst layers, water flooding, to name just a few. Exploring novel biomimetic designs may offer solutions to these challenges.

This research is inspired by vascular plant structures to improve mass transport and efficiency. The cathode uses carbon nanofibers (CNF) made via electrospinning, with Pt nanorod catalyst on the surface in an open electrode layout. This CNF-type cathode was used to create a membrane electrode assembly (MEA), using a commercial membrane and typical anode. A number of parameters were varied, including overall Pt loading, Pt concentration on the fibers, design with and without gas diffusion layer, using CNF mat. The MEAs were tested to establish links between structure, properties, and performance. Performance was evaluated through polarization curves and electrochemical impedance spectroscopy, while beginning of test and end of test structure was investigated using microscopy. CNF-based MEAs achieved a higher current density compared to the commercial MEA at lower Pt loading. This suggests that reduced loading still maintained acceptable Pt utilization, reducing the Pt amount in the MEA. In summary, the CNF catalyst support displayed improved durability, mass transport, Pt utilization, and efficiency thanks to its porous mesh structure.
Sustainable Production of Hydrogen through High-Temperature Molten Salt Electrolysis
Authors: Kamali Ali Reza
Published: August 2024

The green and cost-effective production of strategic materials, including steel on a large scale is pivotal for fostering sustainable industrial development. Hydrogen emerges as a key component for clean steel production, but its sustainable and economical generation remains a barrier to widespread utilization in iron and steelmaking, as well as other applications. Conventional water electrolysis, a common method for carbon-free hydrogen production, faces economic challenges, equipment corrosion, and the use of expensive catalysts with high over-potentials, limiting its viability. Additionally, the transportation of hydrogen from the electrolyzer to utilization units poses cost and safety concerns. Addressing these challenges, this presentation discusses the electro-generation of hydrogen in high-temperature molten salts. The generated hydrogen can then be utilized in situ for the production of metals, alloys, and other commercially valuable materials. Leveraging high temperatures improves the thermodynamic potential and efficiency of the water-splitting process. Remarkably, electrolytic hydrogen produced in molten salts, operating at a potential of around 1 V, has the capacity to facilitate the production of a diverse range of materials such as Fe, Mo, W, Ni, and Co-based alloys.

References

K. Xie, A.R. Kamali*, Energy Convers. Manag. 251 (2022) 114980

D. Qiao, K. Xie, A.R. Kamali*, Mater. Adv. 1 (2020) 2225

K. Xie, A.R. Kamali*, Int. J. Hydrogen Energy 44 (2019) 2 4353

A.R. Kamali*, RSC Advances 10 (2020) 36020

A.R. Kamali, US2021009415 (2023)

K. Xie, A.R. Kamali*, Green Chem.21 (2019)198
Fe-MOF-74 Reactivity Explored: Comprehensive Computational Assessment of O and S Atom Influence on CO2 and CO Reduction Reactions
Authors: McCarver Gavin , Yildirim Taner , Zhou Wei
Published: August 2024

The conversion of carbon dioxide (CO2) and carbon monoxide (CO) into higher-value materials is crucial for addressing escalating levels of greenhouse gases in Earth’s atmosphere. Employing first-principles methods, we investigated the electrocatalytic reduction of CO2 and CO on two Fe-based MOFs: Fe2DOBDC and Fe2DSBDC. By directly comparing these MOFs, we aimed to discern the impact of introducing S atoms into the framework without changing the topological framework. Several chemical properties such as electronegativity, atomic radius, polarizability, and charge density are expected to lead to significant changes for the reduction reactions upon the replacement of O atoms with S atoms. CM5 atomic charge analysis highlights some of these differences by showing the equatorial Fe-O/S bonds of Fe2DSBDC are less polarized and result in smaller positive and negative charges on the Fe and O/S atoms, respectively. Additionally, the larger S atoms are expected to weaken adsorbate binding due to less favorable van der Waals interactions near the open-metal Fe site. Consequently, the less electropositive Fe site and the larger S atoms of Fe2DSBDC impede the adsorption of reduced CO2 and CO products, while the more electropositive Fe site and smaller O atoms of Fe2DOBDC strongly favor product adsorption. This implies that CO2 and CO reduction on Fe2DSBDC is likely to yield only 2e- products (HCOOH and CH2O, respectively), whereas Fe2DOBDC is expected to produce deeper reduction products (CH2O and CH4, respectively). This insight offers a foundation for constructing novel MOFs with tunable reaction behaviors by strategically replacing O atoms with heavier S atoms in the MOF scaffold.
(Invited) Department of Energy, Energy Efficiency and Renewable Energy - Activity Updates in Reversible Fuel Cells and High Temperature Electrolysis
Authors: Gibbons William , Ho Donna , Papageorgopoulos Dimitrios C. , Peterson David
Published: August 2024

The Hydrogen and Fuel Cell Technologies Office (HFTO) within the U.S. Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy (EERE) supports a range of analysis, research, development, and demonstration efforts that fall under the areas of high temperature electrolysis (HTE) and reversible fuel cells (RFCs). These efforts range from earlier stage R&D on cell components to demonstrating early system technology. Particularly when used in conjunction with high temperature process heat, HTE technology shows promise for highly efficient, cost effective, sustainable hydrogen production at high volumes. This potential has led to its inclusion in multiple HFTO initiatives, including two national lab-led consortia separately focused on next generation materials and overcoming technical barriers to manufacturing durable, affordable, and efficient HTE systems. These consortia objectives, efforts, scopes, and developments are discussed in the context of HTE and recent DOE initiatives and announcements, including the Hydrogen Energy Earthshot, Long Duration Energy Storage Earthshot, and Clean Fuels and Products Earthshot.
Theoretical Understanding of Stability of the Oxygen Electrode in a Proton-Conductor Based Solid Oxide Electrolysis Cell
Authors: Wang Yudong , Marchetti Barbara , Zhou Xiao-Dong
Published: August 2024

The oxygen electrode in a proton-conductor based solid oxide cells is often a tripleconducting material that enables the transport and exchange of electrons (e), oxygen ions (O2), and protons (H+), thus expanding active areas to enhance the oxygen electrode activity. In this work, a theoretical model was developed to understand stability of triconducting oxygen electrode by studying chemical potentials of neutral species (i.e., μO2 , μH2 , and μH2O) as functions of transport properties, operating parameters, and cell geometry. Our theoretical understanding shows that (1): In a conventional oxygen-ion based solid oxide cell, a high μO2 (thus high oxygen partial pressure) exists in the oxygen electrode during the electrolysis mode, which may lead to the formation of cracks at the electrode/electrolyte interface. While in a proton-conductor based solid oxide cell, the μO2 is reduced significantly, suppressing the crack formation, and resulting in improved performance stability (2). In a typical proton-conductor based solid oxide electrolyzer, the dependence of μO2 on the Faradaic efficiency is negligible. Hence, approaches to block the electronic current can improve the electrolysis efficiency while achieving stability (3). The difference of the μO2 (thus pO2 ) between the oxygen electrode and gas phase can be reduced by using higher ionic conducting components and improving electrode kinetics, which lead to further improvement of electrode stability.
In-Situ structural and Adsorbate Induced Surface Evolutions Monitored By Electrochemical Stress Measurements
Authors: Tavassol Hadi
Published: August 2024

We report on in-situ electrochemical stress measurements of well-defined surfaces during electrochemical reactions in aqueous media. Electrochemical stress measurements during hydrogen evolution reaction (HER) on Pt surfaces shows distinct pH-dependent features which we assign to anion adsorption/desorption and hydrogen adsorption/desorption. Our surface stress analysis shows higher hydrogen induced stresses at alkaline environments than stresses observed at acidic pHs. This observation is consistent with the monotonic change in apparent hydrogen binding energy with pH, most likely due to the changes in water interactions with surface. However, H-induced surface stress shows a dramatic increase around neutral pH. We will present our analysis of how interfacial water may explain this effect. Additionally, we will show how in-situ underpotential deposition of Cu on Pt and Ni on Au changes Had induced effects on these surfaces.

We will also discuss the structural and compositional evolution of Sr2Fe2O6-δ thin films during oxygen evolution reaction (OER). Interestingly, in-situ electrochemical stress measurements show a tensile stress response during OER which is different from Au model surfaces. We will present our analysis of how potential controlled formation of iron (oxy)hydorxides may explain in-situ stress response and structural evolution of perovskite type structures during OER.

In summary, our analysis shows how adsorbate-induced effects can be used to explain surface reactions, and particularly explain and provide insight into interfacial structural changes and water interactions at different pHs.
(Invited) Electrochemical Processes Drive Membrane-Based Recovery of N and P
Authors: Jassby David , Iddya Arpita
Published: August 2024

We expend a large amount of energy and money on the treatment of municipal and industrial wastewater, relying on redox reactions to transform contaminants (e.g, ammonium, reduced carbon) into other less/non-harmful species (N2/NO3
-, CO2), or on biological accumulation approaches that sequester contaminants into bacteria (e.g., biomass, PO4
-3). In the worst case, these contaminants are simply released into the environment where they cause harm and are lost. Yet, many of these contaminants are actually valuable resources (e.g., NH3, PO4
-3). In an age where environmental sustainability and climate change mitigation are of utmost importance, it makes little sense to invest large amounts of energy into the conversion and elimination of these valuable resources, only to turn around and use fossil fuels to produce more. In addition, the value of these resources is often higher than the value of the treated water, making their recovery an economically-attractive prospect.

Here, we discuss our recent work on membrane-based separations of ammonia, phosphate, and volatile fatty acids (VFAs) from different waste streams. Critically, in all cases we achieve separation by leveraging electrochemical reactions and processes. For ammonia recovery, we utilize an electroactive membrane contactor that is used as a cathode – the application of cathodic potentials to the membrane surface increases the local pH at the membrane/water interface, which transforms ammonium to ammonia and enables its effective volatilization and recovery across the membrane. For VFA recovery, we use a composite electroactive membrane that combines electrothermal heating and an electrochemical pH swing to protonate and extract these volatile species from water. Finally, for phosphate separation, we engineer a phosphate-specific pathway through a cation exchange membrane, and use electrodialysis to pull phosphate ions from a mixed anion solution. Together, these approaches can be used to recover valuable products from complex waste streams, such as municipal and industrial wastewater, without the need to rely on bulk pH and temperature modification.
(Invited) Green Ammonia Production from Electrochemically Upcycling Waste Nitrogen in an Membrane-Free Alkaline Electrolyzer
Authors: Li Wenzhen , Chen Yifu , Liu Hengzhou , Gu Shuang
Published: August 2024

NH3 is an essential nutrient for life, but its production through anthropogenic N2-fixing process has caused alarming damages to ecosystems and human health. Excessive NO3
- leakage into water bodies due to overfertilization has led to the formation of "dead zones" in coastal areas. Denitrification generates N2O, which is 300 times more potent than CO2. Restoring the balance between the generation and elimination of Nr is an urgent task for humanity. Efforts to address the negative impact of human-generated Nr have focused on converting it to harmless N2 or improving its utilization in the nitrogen cycle. One promising method is electrochemical conversion, which can eliminate Nr without additional oxidants/reductants. However, achieving selective NO3RR toward N2 is challenging. An alternative approach is to convert other forms of Nr to NH3 in an electrochemical reactor, which could reduce the environmental impact of Nr and decrease the NH3 demand from the Haber-Bosch process, while also reducing the use of fossil-derived H2.

In this work, we report our work on the development of a membrane-free alkaline electrolyzer (MFAEL), which transforms Nr into NH3 as the sole N-containing product. With the inexpensive and robust MFAEL system, we achieved an ampere-level partial current density towards NH3 production. By properly choosing the conditions of NH3 collection from MFAEL, continuous production of pure NH3-based chemicals can be realized without the need for additional separation procedures. Techno-economic analysis (TEA) suggests the potential economic feasibility of the waste-to-NH3 process by coupling electrodialysis (ED) for Nr concentration and the MFAEL process for Nr conversion, offering an all-sustainable route for upcycling waste N into the highest-demanded N-based chemical product. Our recent efforts on green-ammonia capture CO2 and reduction to valuable chemicals will also be briefly presented.
Limitations and Opportunities of Self-Supported Co-Based Anodes for Pure Water-Fed Anion Exchange Membrane Water Electrolyzers
Authors: Kwak Minkyoung , Boettcher Shannon W.
Published: August 2024

Hydrogen has been regarded as an energy source with a potential to be used in various sectors, including transportation, power generation and industrial processes1-3. Producing hydrogen via water electrolysis using green electricity will be necessary for a sustainable future. Proton exchange membrane water electrolysis (PEMWE) is one of mature and leading electrolysis technologies, while anion exchange membrane water electrolysis (AEMWE) is regarded as a new, emerging technology4. However, PEMWE system suffers from their expensive cost and scarcity of iridium-based oxygen evolution reaction (OER) catalysts, having no alternative OER catalysts. Compared to PEMWE, AEMWE can be pursued with non-platinum group metal (non-PGM) thanks to its alkaline environment4,5.

Here, non-PGM Co-based catalyst coated anodes were prepared using a simple hydrothermal reaction followed by heat treatment. Different phases and crystallinity of cobalt-based anodes were prepared and tested in pure water-fed AEMWE devices. To investigate the catalyst-ionomer/membrane interfaces at the anodes, the loadings of Co3O4 catalyst and ionomer topcoats were controlled. The cell performance in polarization curves was correlated with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements. The comparison of anodes operated with pure water feed and with supporting electrolyte was made to highlight the importance of catalyst-ionomer interface in pure water-fed AEMWE. Lastly, our self-supported Co3O4 anode outperformed a commercial Co3O4 NP ink-based anode, projecting a potential of direct growth of catalyst materials on PTLs in pure water-fed AEMWE.

Reference

(1) Agyekum, E. B.; Nutakor, C.; Agwa, A. M.; Kamel, S. A Critical Review of Renewable Hydrogen Production Methods: Factors Affecting Their Scale-Up and Its Role in Future Energy Generation. Membranes
2022, 12 (2).

(2) Qusay, H.; Sameer, A.; Aws Zuhair, S.; Hayder, M. S.; Marek, J. Green hydrogen: A pathway to a sustainable energy future. Int. J. Hydrogen Energy
2024, 50, 310-333.

(3) Joonsik, H.; Krisha, M.; HeeJin, C. A review of hydrogen utilization in power generation and transportation sectors: Achievements and future challenges. Int. J. Hydrogen Energy
2023, 48 (74), 28629-28648.

(4) Lee, S. A.; Kim, J.; Kwon, K. C.; Park, S. H.; Jang, H. W. Anion exchange membrane water electrolysis for sustainable large-scale hydrogen production. Carbon Neutralization
2022, 1 (1), 26-48.

(5) Juchan, Y.; Myeong Je, J.; Xiaojun, Z.; Yoo Sei, P.; Jooyoung, L.; Sung Mook, C.; Yadong, Y. Non-precious electrocatalysts for oxygen evolution reaction in anion exchange membrane water electrolysis: A mini review. Electrochem. Commun.
2021, 131, 107118.
Technical Strategies on Building Loosened Polymertic-Chain Structure at Platinum-Perfluorinated Sufonicacid Ionomer Interface
Authors: Jung Chiyoung , Choi Won young , Choi Hyunguk , Choi Seo won , Park Young Je , Cho Hyeon E
Published: August 2024

For a complete electrification of transportation sector, the hydrogen fuel cells and lithium-ion batteries are considered as promising candidates for electro-chemical energy storage and conversion devices that may utilize the renewable energy. Between them, the PEFCs offer the decisive advantages, such as faster fueling and longer driving range that is especially advantageous for the heavy-duty applications. However, the spread of this technology is blocked by scarcity of platinum group metals (PGMs). Although the state-of-the-art fuel cell electric vehicles (FCEVs) have succeeded in reducing the PGM usage around 20 g per a passenger vehicle until now, over four-folds amount of PGMs must be further reduced to achieve sustainability. Hence, increasing Pt utilization rate in such system is key to everything; however, the performance of PEFC electrode has been severely aggravated under the presence of perfluorinated sulfonicacid (PFSA) ionomer. In this work, we have shown the key comparative features of technical approaches that have been made within literatures in the recent decade including our previous work. More specifically, the electrode ionomer homogeneity of hydrophilic-hydrophobic domains as well as polymeric chain densification at Pt-ionomer interface has been discussed. Finally, some technical pathways to simultaneously resolve the dry accessibility as well as specific adsorption of ionomer are drawn with detailed information. This paper provides a key summary that may be helpful in defining the notorious "RDE versus MEA" issue and also categorizing the possible solutions that are either previously done or will be covered in the near future.