bluuebunny/crossref_metadata_2025_split huggingface dataset:
Benchmarking Local pH of Electrocatalysts for Water Electrolysis Using the Rotating Ring-Disk Electrode Technique
Authors: Wu Wen Yu , Wilkinson David P. , Gyenge Elod L. 
Published: August 2024

Water electrolysis is an important route for production of green hydrogen and remains a field of active research in pursuit of improved electrocatalytic activity and durability. Operating with a near-neutral feed is critical for this technology to be more widely adapted, because it allows the direct use of various water sources and imposes less stringent requirements on the components of the electrochemical cell.
During water electrolysis, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) involving protons and hydroxides can experience a significant change in local pH at the surface of the catalyst, especially in near-neutral bulk conditions. This change in local pH is usually dictated by the reaction conditions such as electrolyte composition and mass transport within the system. Notably, there has been an increase in development of catalysts for water electrolysis with the ability to modulate their local pH in recent years. 1–6

However, comparing and quantifying the local pH modulation effects of these catalysts is challenging due to varying experimental techniques and protocols. The rotating ring-disk electrode (RRDE) with a potentiometric pH sensing ring has been presented as a promising and facile tool for in-situ local pH detection. 3,4,7,8 The local pH at the disk is estimated from the ring pH through solving the convective-diffusion equation under the well-defined mass transport conditions of an RRDE system. 8

In this study, we have investigated the local pH of iridium oxide during OER in both unbuffered and buffered electrolytes under near-neutral to alkaline bulk conditions using the RRDE technique. Our results provide benchmarks for future studies on the local pH modulation effects of catalysts and insights into the impact of electrolyte composition on local pH. In combination with mass transport modelling, we further examined the limitations of this technique and provide suggestions for best practices.

References

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Z. Li et al., Angew. Chemie Int. Ed., 62, e202217815 (2023).

J. Guo et al., Nat. Energy, 8, 264–272 (2023).

X. Zheng et al., Nat. Commun. 2023 141, 14, 1–13 (2023).

X. Wang, C. Xu, M. Jaroniec, Y. Zheng, and S. Z. Qiao, Nat. Commun. 2019 101, 10, 1–8 (2019).

H. Tan et al., Nat. Commun. 2022 131, 13, 1–9 (2022).

Y. Yokoyama et al., Chem. Lett., 49, 195–198 (2020).

W. J. Albery and E. J. Calvo, J. Chem. SOC., Faraday Trans. 1, 79, 2583–2596 (1983).

Figure 1
(Invited) Fruitful and False Analogies between Polymer Electrolyte Fuel Cells and Electrolyzers
Authors: Mittelsteadt Cortney , Yang Fan , Paxson Adam , Sweetland Matthew 
Published: August 2024

In the past 20 years polymer electrolyzer membrane fuel cells (PEMFCs) received great attention as a clean alternative for powering mobility and stationary applications. Resultingly, there has been a rich amount of research by public, private and university investigators particularly focusing on membranes, catalysts, transport and cost. Yields of great advances were made, though scant attention was given to the generation of this hydrogen and polymer electrolyte membrane water electrolysis (PEMWE) was the neglected stepsister, sentenced to back chapters, footnotes, and small conference rooms. Now however the opportunity for hydrogen generated from renewables, "green hydrogen" has been widely seen as an opportunity to not only provide hydrogen for these PEMFC applications, but also seemingly intractable CO2 emitters as ammonia generation and steel and petroleum refining. As numerous government agencies have announced eye-popping targets for green electrolysis and the complementary research funding, the temptation is to take the beautiful evening gown woven of PEMFC research and adorn the overlooked stepsister. .
Zealous PEMFC researchers have not surprisingly reversed course and focused attention on making, rather than consuming hydrogen. Exploitation of the PEMFC and PEMWE analogy is tempting, as many of the materials and reactions are the same or similar. Noteworthy, there are the polymer electrolyte membrane, expensive PGM catalysts, a very fast hydrogen reaction and very slow oxygen reaction. Yearning for faster kinetics and facile heat management, both also have pushed operation to higher temperatures and suffer the accelerated degradation that goes with it. Using these analogies has has generated some benefits, particularly in lower catalyst loading and conductive membrane resistance. Keeping in mind the differences is key however, as PEMWE will generally need to operate at much higher currents, under higher pressures, for far longer durations.
This talk will look at what PEMWE has and has the potential to learn from PEMFC research. We will look at materials, their key aspects and how optimizing for each is different, with a focus on costs, the use of hydrocarbon materials, chemical and mechanical durability strategies and recycling. Use cases will also be explored, particularly how the need for high hydrogen production pressures (>30 bar) changes the electrode assembly as well as the balance of stack.
Investigating the Differences between the in-Situ Galvanostatic Test and Ex-Situ Fenton Test on Nafion Membranes for PEM Water Electrolysis
Authors: Patra Sudeshna , Gottschalk Torben , Heßling Janis , Trinke Patrick , Schweer Felix , Bittner Florian , Schönhoff Monika , Bensmann Boris , Hanke-Rauschenbach Richard 
Published: August 2024

Perfluorinated sulfonic acid (PFSA) ionomer membranes (e.g Nafion) are widely employed as the benchmark materials for the electrolyte membranes in PEM water electrolysis (PEMWE). It is broadly acknowledged that the state of health of PFSA membranes is detrimentally impacted by the chemical degradation occurring during operation of PEMWE. The cross-over gases interacting with the catalytic surface lead to the generation of hydrogen peroxide. This compound can undergo homolytic cleavage or, in the presence of ferrous salts, yield reactive oxygen species such as hydroperoxyl (HOO.) and hydroxyl (HO.) radicals. These radicals attack the ionomer subsequently leading to chain scission, unzipping and loss of functional groups and release of HF in the effluent water. However, the degree of degradation differs when exposed to ex-situ conditions compared to real proton exchange membrane (PEM) water electrolysis conditions.
This work depicts a methodical investigation of degradation of catalyst coated Nafion membranes (CCM) using a Fenton's accelerated aging experiment and in-situ test. In the Fenton's approach, the durability of Nafion 117 and catalyst coated Nafion membrane with counter ions such as ferrous ions against H2O2 was explored as a degradation factor of polymer electrolyte water electrolyser. CCMs were submerged to a solution containing ferrous ions and peroxide. Accelerated aging experiments were conducted over a period of 3-7 days. An in-situ ageing test has been performed on a MEA with and without the presence of Ferrous ions by applying galvanostatic pulses for 7 days. Experimental confirmation of degradation mechanisms has been obtained by post-mortem analysis of the MEA using microscopy and chemical analysis and mechanical investigation. To quantify the effect of water activity in Nafion and CCM chemical structure on both water diffusion and interfacial transport, pulse field gradient spin echo nuclear magnetic resonance (PFGSE-NMR) technique has been employed. Morphological characteristics before and after aging tests were also investigated. Comparative estimation of the fluoride release rate in case of both in-situ and ex-situ test was also performed. This work offers a comprehensive dataset comparing the performance of degraded membranes both in situ and ex situ.
Materials Integration and Catalyst Interfaces in Anion Exchange Membrane, Low Temperature Electrolysis
Authors: Alia Shaun M , Kreider Melissa E , Volk Emily K. , Chan Ai-Lin , Ul Hassan Noor , Clauser Arielle L , Sugar Josh D 
Published: August 2024

Hydrogen has unique advantages as an energy carrier due to its high energy density and abilities in long-term storage and to convert between chemical bonds and electricity. [1] Although hydrogen currently has a small role in energy pathways, decreasing electricity prices can allow for significant growth. Anion-exchange-membrane water electrolysis (AEMWE) holds promise for reaching reduced hydrogen production cost targets, particularly from a materials perspective, and is the primary technology pathway being studied under Low Temperature Electrolysis in the HydroGEN Energy Materials Network (EMN).
In AEMWE, it has been critical to explore the impact of materials and their integration on performance and durability, thereby demonstrating and enhancing use opportunities. [2] While platinum group (PGM) -free components, including catalysts and transport layer/separator coatings are readily available that can achieve high performance at a reduced cost, individual properties and their interactions create integration challenges.[3] Specifically in performance, the inclusion of ionomer and pore structures can be more complicated than for acidic systems and the use of PGM-free materials can add difficulties in electronic and ionic transport. While AEMWE can become extremely durable when targeted for low-cost applications, additional loss sources including ionomer oxidation, materials passivation (catalyst, transport layer, separator) further complicates identifying and separating irreversible loss mechanisms, and in developing accelerated stress tests. This presentation includes an overview of efforts in AEMWE and focuses on materials choices, catalyst-ionomer-transport layer interactions, and the variety of integration strategies being employed in the HydroGEN EMN.
References
[1] B. Pivovar, N. Rustagi, S. Satyapal, The Electrochemical Society Interface
2018, 27, 47.
[2] S. Alia, D. Ding, A. McDaniel, F.M. Toma, H.N. Dinh, Chalkboard 2-how to make clean hydrogen. The Electrochemical Society Interface
2021,
30 (4), 49.
[3] S. M. Alia, HydroGEN: Low Temperature Electrolysis, https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/review23/p148a_alia_2023_p-pdf.pdf 2023.

Figure 1
Surface Engineered Ni-Fe Foam As a Bi-Functional Electrode for Water Electrolysis in Alkaline Media
Authors: Aly Islam A , Abdelsalam Mohamed O , El Sawy Ehab N 
Published: August 2024

Using fossil fuels as a main source of energy has resulted in various environmentally hazardous effects, including global warming, climate change, and environmental pollution. Consequently, the development of a sustainable and clean source of energy became of urgent need. Water electrolysis has captured considerable attention as the main technology of hydrogen fuel production. It is particularly enticing due to its eco-friendliness and sustainability. Self-supported electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) have prominent roles in water electrolysis. Growing self-supported metal oxides, hydroxides1, phosphates2, sulfides3, etc. that possess high electrical conductivity, electrocatalytic activity, and structural stability have attracted attention lately. FeNi-based catalysts are considered one of the most promising electrocatalysts for water electrolysis in alkaline solutions. However, improving their catalytic activity and stability is one of the research targets before further practical applications. Nickel foam is widely used as a self-supported electrocatalyst due to its high surface area, low cost, and exceptional catalytic activity, with several studies focused on the deposition of nickel-iron materials on nickel foam for the development of a bifunctional catalyst for water electrolysis4. However, very few studies used NiFe mesh or foam to grow a self-supported catalyst material5.
In this study, surface-engineered NiFe foam electrodes were developed by facile control of the Ni/Fe surface ratio via chemical leaching and oxidation with NaOH and NaClO4 followed by electrochemical activation, aiming to design a bifunctional electrocatalyst for both OER and HER. Results revealed that varying the ratios of NaOH and NaClO4 induced significant alterations to the surface composition (different Ni/Fe), and hence the active sites for OER and HER. The physicochemical and structural properties of the NiFe foam were characterized using glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). Further, the catalytic activity of the modified electrode was assessed utilizing cyclic voltammetry, linear sweep voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy.

References

F. Dionigi and P. Strasser, Advanced Energy Materials, 6, 1600621 (2016).

Y. Yu et al., Journal of Colloid and Interface Science, 607, 1091–1102 (2022).

A. Shankar, R. Elakkiya, and G. Maduraiveeran, New J. Chem., 44, 5071–5078 (2020).

H.-S. Hu, S. Si, R.-J. Liu, C.-B. Wang, and Y.-Y. Feng, International Journal of Energy Research, 44, 9222–9232 (2020).

C. Sun et al., ACS Appl. Energy Mater., 4, 8791–8800 (2021).
Low Ir-Containing Materials As Anode Catalysts for PEM Water Electrolysis
Authors: Surkus Annette-Enrica , Pham Trang Minh 
Published: August 2024

The PEM electrolysis is based on the application of IrO2 as anode catalyst. Until now, there is no real alternative for this electrocatalyst, since the highly acidic and oxidative conditions at the anode lead to rapid corrosion.[1-3] With steadily increasing energy consumption, the demand for iridium will exceed the available resources in a few decades. As a result, the price of iridium as well as the technologies based on it will continuously increase. An enhancement of PEM electrolysis capacities on a large scale can therefore only be realized in the long term if the application of iridium is significantly reduced.[4] Therefore, our research aims at reducing the iridium content of PEM anodes while maintaining catalytic activity and stability.
In this work, two approaches to save iridium were applied. On the one hand the iridium content was reduced by supporting it, on the other hand an additional, readily available metal is incorporated that is protected from corrosion by the presence of iridium and at the same time assists the iridium in catalysis.
So, bimetallic included low-loading Ir and different transition metal (Ru, Sn, and Ag) nanoparticles on titanium nitride (TiN) were synthesized by using a chemical reduction method and thermal treatment. Experimentally, a IrSnOx/TiN sample in 0.5 M H2SO4 with an Ir loading of 0.05 mgIr/cm2 achieves a mass activity of over 450 A/gIr at 1.6 V vs RHE and an overpotential of 297 mV at 10 mA/cm2. The investigation includes stability tests at constant current density of 10 mA/cm2 and determination of impedance by electrochemical impedance spectroscopy (EIS).
As result, a suitable anode material was successfully achieved, which exhibits a similarly good activity and stability values compared to the IrO2 materials that have been used industrially so far, but with a significantly reduction of iridium to 24% of the usually applied amount.
[1] C. Minke, M. Suermann, B. Bensmann, R.H. Rauschenbach, Int. J. Hydrog.
Energy, 2021, 46, 23581-23590.
[2] F. Scarpelli, N. Godbert, A. Crispini, I. Aiello, Inorganics,
2022, 10, 115.
[3] J. Gao, Y. Liu, B. Liu, K.W. Huang, ACS Nano, 2022, 16, 17761-17777.
[4] T. Reier, H. N. Nong, D. Teschner, R. Schlögl, P. Strasser, Adv. Energy Mater., 2017, 7, 1601275.
Pristine Metal-Organic Frameworks for Efficient Oxygen Evolution Electrocatalysis
Authors: Šljukić Biljana , Paul Anup , Santos Diogo M.F 
Published: August 2024

Green energy technologies propose the use of hydrogen as fuel instead of fossil fuels that have drawbacks of limited supplies and greenhouse gas emission during their combustion. Though hydrogen is the most abundant element on the Earth, hydrogen gas is commonly not found in pure form, but bound in compounds such as water or hydrocarbons. Thus, hydrogen gas is a synthetic fuel that needs to be produced. For the energy to be completely green, hydrogen should be produced using renewable energy. Currently, most of the hydrogen is produced using fossil fuels and only ca. 5% is produced using electrolytic water splitting. It is the high cost of the water-splitting process that limits its use on the wider scale. To reduce the associated high energy input to break a water molecule, resulting in high cost of hydrogen produced by water splitting, expensive electrocatalysts are typically used.
The aim of this work is to design novel and low cost metal-organic frameworks (MOF) or coordination polymers (CP) utilizing different ligands (for instance, amide functionalized ligands) towards their application in energy conversion reactions such as oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). MOFs are rarely used in their pristine form; literature reports typically focus on MOF-derived carbon materials. Moreover, herein special attention is given to OER as the efficiency-limiting reaction within the water electrolysis process.
The first part of the work focuses on the synthesis and characterization of ligands and MOFs/CPs based on transition metals, nickel and cobalt. The morphology and structure of these composites is examined using electron microscopy and X-ray diffraction analysis. The second part of the work focuses on the pristine materials’ electrocatalytic activity involving standard electrochemical techniques, i.e., voltammetry, impedance spectroscopy, and chronoamperometry to identify the material with the optimum performance and stability. Main reactions parameters including onset potential, overpotential at defined current density as well as current density at defined potential and Tafel slope, are determined.
This work presents step towards green hydrogen production within search for solutions for the current energy crisis.

Acknowledgments

This work was supported by the Science Fund of the Republic of Serbia, grant number 7750219, Advanced Conducting Polymer-Based Materials for Electrochemical Energy Conversion and Storage, Sensors and Environmental Protection-AdConPolyMat (IDEAS programme).
Effectiveness of Gas Recombination Catalyst Layers in Mitigating H2 Crossover in PEM Water Electrolyzers Operating at High Differential Pressure
Authors: Gawas Ramchandra , Lee Jason Keonhag , Dizon Arthur , Wang Guanzhi , Kushner Douglas I. , Peng Xiong , Mukundan Rangachary 
Published: August 2024

Gigawatt-scale deployment of proton exchange membrane water electrolyzers (PEMWE) to produce green hydrogen at $1/kg of H2, the US department of energy’s (DOE) ultimate cost target, requires the use of thinner membranes to reduce ohmic losses at high current densities as well as differential pressure operation to improve the overall system efficiency.1 High differential pressure operation results in significant hydrogen crossover through PEMs leading to safety concerns due to the formation of a flammable gas mixtures at anode (> 4% H2 in O2).2 Therefore, the successful deployment of PEMWEs at scale relies on successful implementation strategies to reduce the hydrogen concentration at anode to enable safe operation at high efficiency. These strategies include incorporating gas recombination catalyst (GRC) in the membrane, PTL or downstream in the anode gas outlet. However, the impact of GRC layers on PEMWE performance and hydrogen crossover rates at high differential pressure is not well understood.
In this work, we employ in-operando gas chromatography coupled with thermal conductivity detector along with PEMWEs operating at differential pressures (up to 30 bar) to quantify hydrogen crossover rates through PEM at differential pressure. Using this setup, we evaluate the effectiveness of gas recombination layers incorporated in PEMWE membrane electrode assemblies (MEA) in mitigating the risk of formation of the flammable gas mixture. Further, we will also discuss implications of high differential pressure operation on PEMWE performance, durability, and operational safety.
References:
(1) Ayers, K.; Danilovic, N.; Harrison, K.; Xu, H. PEM Electrolysis, a Forerunner for Clean Hydrogen. Electrochem Soc Interface
2021, 30 (4), 67–72. https://doi.org/10.1149/2.F16214IF.
(2) Bernt, M.; Schröter, J.; Möckl, M.; Gasteiger, H. A. Analysis of Gas Permeation Phenomena in a PEM Water Electrolyzer Operated at High Pressure and High Current Density. J Electrochem Soc
2020, 167 (12), 124502. https://doi.org/10.1149/1945-7111/abaa68.
Investigation of Iridium Catalyst Degradation in PEM Water Electrolyzers: Current Density or Cell Voltage?
Authors: Sun Qiang , Mittelsteadt Cortney , Buek Connor , Yang Fan , Jia Qingying 
Published: August 2024

Proton exchange membrane (PEM) water electrolyzers represent a cornerstone technology in the sustainable production of green hydrogen. However, their large-scale commercialization is hindered by catalyst degradation, particularly the iridium-based anode, which compromises the efficiency and durability of the stack. This study delves into the degradation mechanism(s) of the Ir-based catalyst in the anode of PEM electrolyzers, focusing on the influence of operating conditions such as current density and cell voltage. We have utilized the state-of-the-art R&D platform “PEMI” at Plug Power to construct a rainbow stack that contains several 50 cm2 membrane electrode assemblies (MEAs) with different membrane thicknesses. This innovative approach enables identical current densities across different MEAs while varying the cell voltage on the anode catalyst layer, thereby isolating the effect of cell voltage from current on catalyst degradation.
Our investigation seeks to clarify the puzzle whether it is the current density or the cell voltage that determines the transition and degradation of iridium-based catalysts. Preliminary results indicate that different oxidation states of Iridium exhibit significantly different kinetics and conductivity at varied cell voltages. This is corroborated by our synchrotron-based in situ X-ray absorption spectroscopy experiments that unraveled evolution of the anode catalyst layer at elevated cell voltages. By systematically analyzing the degradation patterns of MEAs with different membrane thickness under controlled conditions, we pinpointed the operational parameter that drives catalyst degradation. The finding provides in-depth understanding of the underlying principles that govern the iridium-based catalyst durability and points to strategies mitigating the degradation. It will pave the way for more resilient and efficient PEM water electrolyzers.

Acknowledgement. This research used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory Contract DE-SC0012704. Beamline operations were supported in part by the Synchrotron Catalysis Consortium Grant DE-SC0012335.
Keywords: PEM water electrolyzers, catalyst degradation, iridium, current density, cell voltage, MEAs.