bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developing Catalysts for Proton and Anion Exchange Membrane Water Electrolyzers
Authors: Jeon Sun Seo , Lee Hyunjoo 
Published: December 2024

To achieve carbon neutrality, extensive research is ongoing to produce green hydrogen via water electrolysis combined with renewable energy sources. Understanding and developing catalysts for membrane electrode assembly (MEA) type water electrolysis systems, such as proton exchange membrane water electrolysis (PEMWE) and anion exchange membrane water electrolysis (AEMWE), are critical steps toward this goal. Therefore, this presentation will focus on catalyst development for PEMWE and AEMWE, with emphasis on cost-effective catalysts.
For oxygen evolution reaction (OER) catalysis in PEMWE, the primary challenge is to minimize iridium (Ir) usage for sustainable green hydrogen production. Layered monoclinic iridium nickel oxide (IrNiOx) platelets were synthesized using a molten salt method and employed for the OER. These platelets exhibited high OER activity with reduced Ni dissolution in acidic conditions. When applied in MEA, they demonstrated enhanced interconnectivity within the catalyst layer, promoting electron transfer. Even at low Ir loading (0.2 mgIr cm-2), the platelets showed good performance with an initial cell voltage of 1.70 V at 1 A cm-2 and minimal degradation over 100 hours. This highlights the effectiveness of incorporating transition metals into Ir oxide to reduce Ir usage in PEMWE.
For oxygen evolution reaction (OER) catalysis in AEMWE, attention is focused on nickel iron (NiFe) hydroxide catalysts for their high activity and stability in alkaline conditions. However, the lack of initial electrical conductivity of as-prepared NiFe LDH limits its potential as an electrocatalyst. To address this issue, a monolayer structuring approach was proposed. This method improved mass transport to allow a high energy conversion efficiency of 72.6% with exceptional stability over 50 hours at 1 A cm-2. Additionally, lack of initial electrical conductivity hinders determination of electrochemically active surface area (ECSA) of NiFe LDH using conventional double layer capacitance method. Use of electrochemical impedance spectroscopy (EIS) at reactive OER potentials to extract the capacitance that is hypothesized to arise due to reactive OER intermediates (O*, OH*, OOH*) adsorbed on the catalyst surface was thus investigated. This allowed the estimation of ECSA and intrinsic activity of NiFe LDH, validating the methodology through rigorous catalyst loading and support studies.
For hydrogen evolution reaction (HER) catalysis in AEMWE, replacing platinum (Pt) with Ni-based alloys containing molybdenum (Mo) species has shown promise. Dynamic active sites of Ni catalysts with Mo species require innovative approaches to maintain initial performance, warranting material innovation or careful manipulation of operating protocol. The approaches in which this is made possible is shortly presented, together with the innovations that allows probing of such phenomenon.
Poly(fluorene)-Based Anion Exchange Membranes with an Interstitial Alkyl Chain in Polymer Backbone and Conducting Groups for Water Electrolysis
Authors: Park Taiho 
Published: December 2024

The demand to reduce fossil fuel dependence has received unprecedented attention due to the generation of greenhouse gases and increase in energy consumption. Hydrogen is considered an ideal energy carrier for building a global renewable energy system owing to its numerous benefits, such as high energy efficiency and nontoxicity. However, more than 95% of hydrogen is produced by reformation of natural gas, which is a nonrenewable energy source with high carbon emissions that predominantly consists of methane. To realize hydrogen as a true alternative to fossil fuels, it must be produced in an environmentally friendly and sustainable manner, which is also known as green hydrogen. One approach to generating green hydrogen is by water electrolysis to split water, which is an essentially unlimited resource.
Current approaches to water electrolysis currently use proton exchange membranes, but anion exchange membranes (AEMs) operate under alkaline conditions and thus allow the use of platinum group metal (PGM)-free metals as electrocatalysts, which makes them a more cost-effective alternative. However, AEM water electrolysis (AEMWE) is limited by unsatisfactory cell durability and performance due to the poor physicochemical stability under alkaline conditions and low hydroxide conductivity of the AEM. Therefore, AEMs need to be improved in terms of their mechanical properties, dimensional stability, and alkaline stability to ensure cell durability and in terms of their hydroxide conductivity to ensure cell performance.
For AEMs, an important step in improving the efficiency and durability of the cell is to enhance the ion conductivity and chemical stability of these materials, which are vulnerable to hydroxide. The stable operation of AEMWE under high alkaline conditions and elevated temperatures is necessary; hence, the spacer-type cation groups anchored from the backbone and aryl ether-free based polymers are a promising candidate for tolerating harsh alkaline conditions.
Thus, we newly designed various type of aryl ether-free poly(fluorene)-based AEMs with interstitial alkyl chains in the conducting groups and a polymer backbone for water electrolysis. The rationally designed AEMs not only demonstrated excellent mechanical properties, high alkaline stability and satisfactory hydroxide conductivity, making them excellent cell performance and durability of the AEMWE. The resulting single AEMWE cell using synthesized AEM demonstrates a voltage decay rate of 2 mV kh−
1 at 1.0 A cm−
2, significantly lower than those reported for AEMWEs and Nafion-based PEMWEs. Additionally, a large-sized 1-cell AEMWE stack utilizing PFPBPF-4-QA with an active area of 63.6 cm2 acheived an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh−1 for 2,000 h,with over 90% of the initial efficiency maintained for over 49,095 h through exponential fitting calculation.
Ion-Conducting Polymers with Intermolecularly Interacting Groups for Improved Cell Performance and Durability of Anion Exchange Membrane Water Electrolysis
Authors: Min Kyungwhan , Kim Tae-Hyun 
Published: December 2024

Green hydrogen production technology has drawn much interest due to its high energy density and eco-friendly energy production of hydrogen. In particular, anion exchange membrane water electrolysis (AEMWE) have been at the core of recent research because of the low cost of hydrogen production by using a non-precious metal catalyst and non-fluorinated ion-conducting polymer electrolyte membranes. Nevertheless, the poor durability and low performance of AEMWE, due to chemical degradation of AEMs in alkaline conditions and the low diffusivity of OH-, need to be addressed for practical use of AEMWE.
In this study, we developed a novel ion-conducting polymers with intermolecularly interacting groups as novel AEMs. This newly developed polymer-based AEMs, exhibited high ion conductivity and excellent alkaline stability, and showed good WE cell performance and durability when applied to AEMWE. The use of this polymer as an ionomer in AEMWE application also showed a promising result.
The details of the synthesis, characterization of the new polymers, and AEMWE cell performance will be detailed.
A Novel Inorganic Proton Conductor for the Catalyst Layer of HT-PEMFC
Authors: Zhai Yunfeng , Qi Jing , Bethune Keith 
Published: December 2024

To develop a novel electrolyte with high proton conductivity under high temperature and low humidity for the cathode catalyst layer of high temperature proton exchange membrane fuel cells (HT-PEMFC), a multilayer structure inorganic material is synthesized with varying oxidation states transit metal complex by refluxing and hydrothermal methods. A fast proton transport pathway is established in the inorganic material by inserting H-bond ligands in the layered structure. With the preliminary tests, the electrolyte powders demonstrate a bulk conductivity of ~10-3 S cm-1 and a particles boundary conductivity of ~10-6 - 10-4 S cm-1 in the temperature range of 20 - 150 °C without humidification, as shown in Figure 1. The boundary conductivity increases with the increasing of testing temperature up to 110 °C then decreases rapidly; but the bulk conductivity barely changes within the testing temperature range. The thermal gravimetric analysis (TGA) indicates the material is stable up to 350 °C in nitrogen (N2) or helium (He). The properties and performance of the material will be further characterized and evaluated; and the structure and composition will be determined. The material will be integrated into the cathode catalyst layer of HT MEAs, and the MEA performance will be evaluated at 120 - 180 °C and low humidity.
Figure 1. The proton conductivity of the inorganic particles at temperature of 20 - 150 °C

Figure 1
(Invited) Membrane-Electrode-Assembly Design Strategy for PA-Based High Temperature Proton Exchange Membrane Fuel Cells
Authors: Lim Katie Heeyum , Lee So Young , Kim Yu Seung 
Published: December 2024

High temperature proton exchange membrane fuel cells (HT-PEMFCs) have attained much attention for recent decades, as providing several merits over low temperature PEMFCs (LT-PEMFCs) such as simplified fuel cell system and wider applicable fuel options from high CO tolerance.
To date, most studies on HT-PEMFC have been focused on phosphoric acid-doped polybenzimidazole (PA-PBI) based system. Worth to note, the durability of this PA-PBI based system is still controversial, showing limited durability under dynamic condition, i.e. high current density, repetitive start up/shut down, thermal cycle, etc., which is due to PA loss from the membrane-electrode-assembly (MEA). To address this issue and further enhance the efficiency and durability of HT-PEMFC systems, a new concept of ion-pair HT-PEMFC was recently introduced. This concept has led to high HT-PEMFC performance with ~ 800 mW cm-2 peak power density under air condition and longer durability over 2,500 h, especially showing a superior durability to conventional HT-PEMFCs based on polybenzimidazole (PBI) membranes.1

Here, we investigate how PA works and moves in HT-PEMFC MEAs, both for PA-PBI based and ion-pair based systems. PA distribution and PA loss in MEAs, which determine the performance and durability of the system, are explored by titration before and after five different accelerated stability test conditions and a clear difference is indicated between PA-PBI system and ion-pair based system.2 Based on these analyses, we suggest our perspectives on MEA design for PA-based HT-PEMFCs.

Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells, Nature Energy, 7, 248 (2022).

Lim, K. H.; Matanovic, I.; Maurya, S.; Kim, Y.; Castro, E. S.; Jang, J-H.; Park, H.; Kim, Y. S. High temperature polymer electrolyte membrane fuel cells with high phosphoric acid retention, ACS Energy Letters, 8, 529 (2023).
(Digital Presentation) In-Situ Quantification of Individual Electrode Polarization and Depth Validation of the Distribution of Relaxation Times Methods Feasibility in PEM Fuel Cell
Authors: Li Lu 
Published: December 2024

The article titled "Dynamics of anion exchange membrane electrolysis: Unravelling loss mechanisms with electrochemical impedance spectroscopy, reference electrodes and distribution of relaxation times" explores the challenges and mechanisms in anion exchange membrane water electrolysis (AEM-WE). The study by Matthias Ranz and colleagues employs electrochemical impedance spectroscopy (EIS), half-cell measurements using a reversible hydrogen electrode (RHE), and distribution of relaxation times (DRT) analysis to delve into the dynamics of AEM-WE cells.
AEM-WE is gaining attention as a promising technology for hydrogen production due to its potential cost benefits over conventional electrolysis systems. However, its adoption faces obstacles such as efficiency issues and high degradation rates. To address these challenges, the research employs detailed electrochemical characterization techniques, providing new insights into the operational dynamics of AEM-WE cells.
The study reveals five major loss mechanisms within AEM-WE systems: hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and ion transport losses, among others, occurring mostly within the catalyst layers. The findings also discuss the influence of various operating parameters on these loss mechanisms and how they can be systematically tracked and analyzed through EIS.
A significant aspect of the research is the application of DRT analysis, a method not previously used in AEM-WE studies. This analysis method helps in identifying and quantifying the different electrochemical phenomena contributing to cell losses. By correlating these phenomena with their physicochemical origins, the study enhances understanding of the underlying processes within AEM-WE cells.
Moreover, the use of equivalent circuit models in conjunction with EIS data provides a deeper understanding of the electrochemical behavior of the system. This combined approach allows for a more precise characterization of the impedance features and the differentiation of processes such as ion transport and electrochemical reactions.
Ultimately, the research highlights the complexity of the AEM-WE process and emphasizes the need for advanced diagnostic tools to optimize performance and stability. By pinpointing the specific causes of efficiency losses and identifying opportunities for material and process improvements, the study contributes significantly to the development of more robust and efficient AEM-WE systems.
In conclusion, the research not only elucidates the various loss mechanisms in AEM-WE but also showcases the potential of advanced electrochemical techniques like EIS and DRT in enhancing the understanding and optimization of this promising hydrogen production technology. This work sets a foundation for future studies aimed at overcoming the limitations of AEM-WE and advancing towards its commercial viability.
An Extendible Multiphysics Model of a Single Water Electrolysis Cell
Authors: Olguín Godoy Vicente , Blaabjerg Frede , Davari Pooya , Frandsen Henrik Lund 
Published: December 2024

The important role that renewable hydrogen has in the energy transition is undeniable given the capability of decarbonizing sectors difficult to electrify acting as the link between electrical energy from renewable sources and molecules for future energy systems. Therefore, improvement of the efficiency, cost and durability of electrolyzer systems is key. The discovery of new materials is one of the research areas in which a lot of effort is focused given that finding more electrochemically active materials allows to reduce overvoltages improving the electrical performance of the electrolyzers. The requirement for these materials is also that they are durable under operating conditions and cheap to produce in order to achieve improvements in all relevant aspects of the technology.
In water electrolysis systems, kinetics, heat management, gas quality, among others, are relevant aspects to understand in order to achieve performance gains. In this line, computational modeling plays an important role in analyzing and understanding the performance of such systems, as well as the effect that different variables have on it. Given the nature of the water electrolysis process, a multiphysics approach is necessary to account for electrochemical, mass transfer, thermal and fluidic processes, as well as their interactions.
Computational models and digital twins are gaining great momentum in electrolysis systems applications, but its availability is limited as its development requires of deep physical knowledge of the different phenomena and their interactions, or large amounts of data. When data is available data-driven models are very useful but the results are not easy to extrapolate when a change in design or materials happens. Therefore, physics-based modelling is a useful tool, as characterization at small scale and short-term is the first step in the discovery of new materials, which allows to obtain physical parameters that act as input for the computational model. This way it is clear that the advantage of developing a physical model is that the model becomes generic, which means that by changing the corresponding design parameters, the performance of a different design can be analyzed.
The current project aims to develop an extendible physics-based model of a single water electrolysis cell. This development will allow to modify different parameters or operating conditions of the cell design and analyze the effect of those changes in the performance. Additionally, the extendible nature allows for its use as single element for analyses in 1D if desired.
The model, developed in OpenModelica, is capable of reproducing the polarization curve of an electrolysis cell, the temperature change between inlet and outlet, the gas crossover and the pressure loss.
(Invited) Catalyst Activity and Durability Evaluations for PEM Water Electrolyzers
Authors: Ioroi Tsutomu , Nagai Tsukasa , Siroma Zyun , Akita Tomoki , Yasuda Kazuaki 
Published: December 2024

To accelerate the deployment of green hydrogen, it is essential to reduce the cost of water electrolyzers in addition to reducing the cost of renewable energy. MW-class PEM electrolyzers are already beginning to be offered worldwide, but they still require many expensive materials such as precious metals, PFSA membranes, and titanium for catalysts, electrolyte membranes, PTL, and separators. Especially iridium is a very limited resource, it is necessary to develop highly active iridium oxide-based catalysts that can reduce the iridium loading of anode to sub-mg-Ir cm-2.
In catalyst development, half-cell evaluation (rotating disk electrode, RDE) is a useful method for rapid primary screening of catalytic activity [1]. To determine appropriate evaluation conditions, the effects of various RDE parameters on half-cell evaluation were examined [2]. Specifically, we searched for conditions that minimize the effects of RDE-specific phenomena such as oxygen bubbles, electrolyte solution, and measurement conditions (evaluation potential, amount of catalyst loading on disk electrode, ionomer ratio, electrode rotation speed, potential sweep rate, etc.). For comparison, the OER activity values (mass activity) were obtained under similar measurement conditions using MEA with the same catalyst. Since the activity values of both are in close agreement, the half-cell evaluation would be valid as an initial activity evaluation for iridium oxide catalysts.
The number of start-up and shutdown of electrolyzers is expected to increase significantly under renewable energy conditions, thus the PEM electrolyzer could deteriorate at an accelerated rate. For example, hydrogen crossover causes the anode potential to drop to near the hydrogen potential during shutdown period. Therefore, the potential of iridium oxide anode tends to fluctuate over a wide range from 0 V to >1.5V vs RHE as it starts and stops, which is considered one of the degradation factors. As an accelerated stress test simulating start-up and shutdown, cycle tests were conducted by repeating constant-current electrolysis (4 A cm-2) and constant-voltage holding (0.1 V) at cell temperature of 40-95℃. The results showed that degradation rate can be up to 15 times faster than that in base-line condition, constant-current electrolysis at 2 A cm-2 at 80°C. At the meeting, we would like to also discuss the degradation factors of MEAs under constant-current and accelerated test conditions.
Acknowledgement: This work was supported by a project, JPNP14021 and JPNP20003 commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
References:

S. M. Alia, G. C. Anderson, J. Electrochem. Soc., 166 (2019) F282.

T. Ioroi, T. Nagai, Z. Siroma, K. Yasuda, Int. J. Hydrogen Energy, 47 (2022) 38506.
Investigating Reverse Current Phenomena Induced by Start/Stop Cycling in Lab-Scale Single-Cell Liquid Alkaline Water Electrolyzers
Authors: Maurya Sandip , Leonard Daniel P , Kang Sun Young 
Published: December 2024

Liquid alkaline water electrolyzers (LAWEs) represent one of the most mature hydrogen production technologies. Large-scale alkaline electrolysis plants have already been deployed at the 100MW scale. Developments advancing LAWEs are crucial in meeting the soaring demand for hydrogen, driven by efforts to combat carbon emissions and transition to cleaner energy sources. Integrating LAWEs with renewable energy sources like wind and solar holds the potential to facilitate the production of green hydrogen at a low cost. However, a significant challenge arises when coupling LAWE with inherently intermittent renewable energy sources. This challenge comes from the reverse current phenomenon following shutdown, which accelerates the degradation of electrolyzer components, including bipolar plates and electrodes. Typically, when an electrolyzer is shutdown, the anode and cathode on the bipolar plate of neighboring cells discharge rapidly. This causes current to flow through the bipolar plates in the opposite direction to normal electrolysis operation. This results in the oxidation of the cathode and the reduction of the anode. While this phenomenon is observed in industrial-scale electrolyzers and multi-cell stacks, it is relatively difficult to replicate in lab-scale single-cell LAWE setups, where bipolar plates are not typically utilized.
Many researchers have proposed various start/stop cycling protocols aimed at mimicking the reverse current phenomenon to study the degradation of electrocatalysts or electrodes in lab-scale LAWE setups. These protocols often involve voltage or current cycling. However, despite these efforts, the reverse current phenomenon and start/stop cycling protocols are not yet fully understood. Additionally, there remains uncertainty on how these findings can be confidently extrapolated to industry-scale LAWE components. In this study, we have systematically examined several start/stop strategies and their impacts on LAWE performance and component durability. Furthermore, we have applied these start/stop cycling protocols to various anode and cathode catalysts to determine whether these protocols are exclusively applicable to conventional nickel electrodes or universal in nature.

The authors would like to acknowledge the support of the U.S. Department of Energy, and the Hydrogen from Next-Generation Electrolysis of Water (H2NEW) Consortium for their support.