bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental Insights into Reaction Centers and Catalytic Mechanisms of Ni- and Co-Based Layered Oxyhydroxides for the Oxygen Evolution Reaction
Authors: Zeng Zhenhua , Dionigi Fabio , Zhu Jing , Liang Junwu , Li Wei-Xue , Strasser Peter , Greeley Jeffrey 
Published: September 2023

Water splitting to generate green H2 fuel and O2 is essential for global CO2 reductions toward net-zero emissions. In this process, however, O2 generation at the anode through the oxygen evolution reaction (OER) is inherently slower by orders of magnitude than H2 generation at the cathode. Thus, improving OER efficiency has been a major effort in electrolysis. Ni-based and Co-based layered hydroxides are among the most active and studied non-previous catalysts in alkaline electrolytes. Although tremendous advances have been made toward improving the activity and the stability of the catalysts over the past decade, there is still a lack of fundamental insights into active sites and reaction mechanisms, which has hindered the establishment of structure-property relationships.
This talk will first provide fundamental insights into reaction centers and catalytic mechanisms of classic Ni oxyhydroxides and Co oxyhydroxides with and without ligand intercalation. We will further discuss the multiple-site synergy in Ni- and Co-based layered double hydroxides (LDH) and ternary hydroxides. We will show that the OER proceeds via a Mars van Krevelen mechanism, starting with the oxidation of bridge OH at the reaction centers with dual metal sites, i.e., M1-OH-M2. We will demonstrate that, to approach the minimum overpotential dictated by a specific OH-OOH scaling relationship, the key is to break the OH-O scaling relationship. A possible route is to form binary metal oxyhydroxides with dual metal sites at the reaction centers or introduce a third element into NiFe LDH or CoFe LDH. If time permits, We will further discuss the role of the non-covalent interaction and polaron-like electronic states in promoting OER at M1-OH-M2 centers.
Faraday Efficiency Study of Pressurized Alkaline Water Electrolyzer
Authors: Zhang Jian (Jim) , Bie Zhenwu , Zhang Huayong 
Published: September 2023

According to a BloombergNEF report, China is the largest green hydrogen market, accounting for about 60% of the expected global electrolysis volume in 2022-2023. More than 90% of these electrolyzers are pressurized alkaline water electrolyzers (AWE), like the classic design of Lurgi. AWE manufacturers and end-users place great emphasis on advanced electrodes and membranes to improve power efficiency, and often using 100% Faraday efficiency to calculate current density-based yields.
As an end-user, the authors investigated a combination of real AWE operating data and electrochemical engineering principles and discovered that Faraday efficiencies were around 85-93%. Therefore, Aspen ACM simulation models were developed based on detailed internal structures and configurations that well corresponded with plant data, suggesting that many AWE manufacturers exaggerate Faradic efficiencies by to 10%.
Some low-cost design improvements are proposed for the bipolar plate and manifold alkali channels, which can improve the Faradaic efficiency by 5-7%, producing higher power efficiency especially when connected to a renewable power source at low loads.
(Invited) Challenges and Opportunities of Alkaline Water Electrolysis
Authors: de Groot Thijs Theodorus 
Published: September 2023

Alkaline water electrolysis has been operated on 100+ MW scale in the 20th century powered by hydropower. Because of this history, the technology is often regarded as a mature technology with limited improvement potential that is less suitable for flexible operation. As a result most research efforts in the field of water electrolysis focus on other technologies such as PEM, solid oxide and AEM electrolysis. This is a pity, since alkaline electrolysis is very well positioned to be deployed on large-scale for the production of green hydrogen in the coming decades. Main reason is that in contrast to the other technologies, alkaline technology does not depend on scarce and/or expensive noble or rare earth metals. Also, the use of a diaphragm instead of a membrane makes the technology more robust.
Yet, to enable the large-scale deployment of alkaline electrolysis for production of green hydrogen from renewable electricity certain technical challenges need to be overcome. These include safety challenges associated with rare scenarios where hydrogen and oxygen can mix, flexibility limitations associated with gas crossover limiting the minimum load of the plant, and durability challenges resulting from frequent shutdowns of electrolyzers. In principle all these challenges can be overcome by rigorous plant design and the selection of suitable diaphragm and electrode materials, but they do require research efforts.
Next to that, there is room to significantly drive down the costs of green hydrogen produced by alkaline electrolyzers. Traditionally, alkaline electrolyzers have been operated at low current densities of 0.2-0.4 A cm-2. This was related to the high ohmic drop associated with the use of thick diaphragms and non-zero-gap cell designs. Presently, advanced alkaline electrolyzers are under development that can operate at significantly higher current densities (~1 A cm-2) through the use of thinner diaphragms, zero-gap cell designs and improved electrode materials. Operation at these increased current densities increases the output of alkaline electrolyzers and in this way can effectively reduce the costs and footprint of water electrolysis plants. Yet, the use of thinner diaphragms and advanced electrodes also creates new challenges, since they can lead to increased gas crossover and vulnerability to impurities and reverse currents that occur upon the shutdown of electrolyzers.
In this presentation the fundamentals of alkaline water electrolysis will be discussed. These include overpotentials and durability of electrode coatings, the role of electrolyte impurities, ohmic resistance, gas crossover through the diaphragm, the influence of operating temperature and pressure, the effect of bubbles, and the influence stray currents resulting from the manifold design. These fundamentals will be translated into a potential design for the perfect alkaline electrolyzer.
Figure:alkaline electrolyzers operational in Norway in 1931. Source: Norsk Industriarbeidermuseum

Figure 1
Multi-Scale Simulations of Bubble Transport in an Alkaline Water Electrolyzer
Authors: Kanemoto Ryo , Suwa Hideki , Tsukase Naruhisa , Araki Takuto , Mitsushima Shigenori 
Published: September 2023

The existence of bubbles can lead to the loss of performance by decreasing the electrochemically active surface area and disrupting the transport of hydroxide ions. These effects caused by the bubbles have yet to be sufficiently clarified. A comprehensive understanding of the mechanisms of dynamics inside an electrolyzer from the molecular scale up to the whole electrolyzer scale is needed. Furthermore, establishing relations between these dynamics at a wide range of scales is important. In this study, numerical simulations of bubble transport coupling fluid dynamics, mass transport and electrochemical reactions were conducted on micro and macro scales, respectively. The micro scale bubble simulation (Fig. 1(a)) incorporates the concentration field of the chemical species into the numerical model and deals with how bubbles grow on and detach from an electrode. In this model, the chemical species generated by the electrochemical reactions dissolve into the liquid phase, and their transfer into the gas phase leads to bubble growth. Since the spatial size distribution of the bubbles can be one of the factors that affect electrolysis performance, in the macro scale bubble simulation (Fig. 1(b)), we study how different sizes of bubbles are transported and distributed inside the electrolyzer. To simulate this phenomenon, a four-phase flow analysis is performed in which small, medium, and large diameters are selected as representatives of bubble diameters, and each is treated as a different phase.
[Acknowledgements]
This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (P14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
Fig. 1 Simulation systems of bubble transport at (a) micro scale and (b) macro scale.

Figure 1
Modelling of a Proton-Exchange Membrane Electrolysis Cell with Liquid-Fed Cathode
Authors: Gerhardt Michael Robert , Østenstad Jenny S , Raynaud Xavier , Barnett Alejandro O 
Published: September 2023

Conventional proton-exchange membrane (PEM) water electrolysers use much thicker membranes (>175 µm) than their PEM fuel cell counterparts (<25 µm), which reduces hydrogen crossover but also reduces electrolyzer efficiency due to the increased Ohmic resistance1. Reduction of hydrogen crossover is critical in conventional systems to avoid buildup of hydrogen in the anode above the lower explosive limit. Due to the use of liquid water at the anode in conventional systems, the anode cannot be flushed with air or an inert gas to reduce the hydrogen concentration.
If the liquid water supply is moved to the cathode, the anode can be easily purged with air, reducing the safety concern related to hydrogen crossover. Proof-of-concept experiments2 have demonstrated the viability of this approach, but many open questions remain regarding the interplay between water transport, water consumption, membrane hydration, and cell performance, as well as understanding what components and properties are most important in improving the efficiency of such a device.
In this work, a framework for modelling of PEM electrolysis cells will be outlined, with special attention to wet and dry anode conditions. The model will be used to provide guidance for optimizing system performance while contributing to understanding of local processes inside an electrolysis cell such as water transport, heat generation, reaction distribution, and bubble formation. We study the impact of various design and operational choices, such as membrane thicknesses, PTL structure, air feed humidity, and differential pressure operation, on the rate of water transport from cathode to anode and on overall cell polarization performance. Using these results, we provide design recommendations for PEM electrolysers with liquid-fed cathodes. Finally, progress towards an open-source implementation of this model will be discussed.
This work has been performed within the HOPE (Revolutionizing Green Hydrogen Production with Next Generation PEM Water Electrolyser Electrodes) and HYSTACK (Low cost, high efficiency PEM electrolyser stack) projects financially supported by the Research Council of Norway under project numbers 325873 and 321466, respectively.

Ayers, K. et al. Perspectives on Low-Temperature Electrolysis and Potential for Renewable Hydrogen at Scale. Annu. Rev. Chem. Biomol. Eng.
10, 219–239 (2019).

Barnett, A. O. & Thomassen, M. S. Method for producing hydrogen in a PEM water electrolyser system, PEM water electrolyser cell, stack and system. Patent No.: WO 2019/009732. EP3649276B1. US11408081B2.
(Invited) Overall Research on Electrode Coating Processes (OREO) - the Role of Imaging and Spectroscopy in Scale-up Fabrication of Low Temperature Water Electrolyzers
Authors: Jankovic Jasna , Ahmadi Maryam , Batool Mariah , Ney Linda , Franzetti Irene , Horstmann Jeronimo , Khandavalli Sunilkumar , Foster Jayson , O. Godoy Andres , Mauger Scott A , Pylypenko Svitlana , Lickert Thomas , Zamel Nada , Smolinka Tom , Groos Ulf 
Published: September 2023

With the recent trends in hydrogen technologies, scale-up fabrication of membrane electrode assemblies (MEAs) for the electrochemical systems such as fuel cells and electrolyzers is gaining significant attention. Companies and researchers are focusing on diverse large-scale electrode fabrication processes, such as roll-to-roll and screen-printing. However, optimizing such processes is not trivial, and a number of parameters, including but not limited to catalyst type, solvent, ink mixing, electrode coating and drying, play a role in the quality of the final product. Correlations between the fabrication parameters and resulting electrode microstructure, properties and performance are important to understand, in order to better control the processes. Imaging and spectroscopy techniques play an important role in this understanding, starting from catalysts, inks and all the way to the electrodes. Information about catalyst distribution, composition, and surface chemistry can be correlated to ink characteristics, and finally to electrode structure, component distribution and properties, and their effect on MEA performance can be investigated.
In this talk, a collaborative work between four institutions, University of Connecticut, Colorado School of Mines, National Renewable Energy Lab and Fraunhofer ISE, within a project on Overall Research on Electrode Coating Processes (OREO), is discussed, with the focus on low temperature water electrolyzers scale-up fabrication and characterization. The talk will especially focus on the role of advanced microcopy and spectroscopy in the characterization of catalyst powders, inks and electrodes.
Electron Microscopy Investigation of Porous Transport Layer Coatings
Authors: Arregui-Mena David , Cullen David A. , Domingo Marimon Neus , Stelmacovich Genevieve , Pylypenko Svitlana , Ware Sam , Bender Guido 
Published: September 2023

The flow of reactants and biproducts to and from the anode in polymer electrolyte membrane (PEM) water electrolyzers is dictated by the properties of the porous transport layer (PTL). The PTL is made of titanium (Ti) fibers or sintered particles to provide stable thermal and electronic conduction pathways at the high overpotentials and acid conditions experienced at the anode. To prevent the formation of a thick native oxide on the Ti PTL surface, precious metal coatings are required. These coatings enable and maintain a reduced interfacial resistance between the PTL and catalyst layer. Understanding the impact of surface treatments and coatings on the morphology and composition of this interface is an important step to minimizing interfacial resistance, degradation and production costs. In this work, ion and electron beam techniques, including focused ion beam (FIB), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and scanning transmission electron microscopy (STEM), are used to investigate PTL coatings at the nanoscale.
A series of fiber-type PTLs with a range of platinum (Pt) coating thicknesses were synthesized using physical vapor deposition. The uniformity of the coatings was analyzed using SEM-EDS in both plan-view and cross-section. Sections of individual fibers were then removed using FIB lift-out technique and thinned to less than 50 nanometers for further analysis by STEM. The thickness and uniformity of the Pt coating was quantified from STEM images for each Pt loading and correlated with interfacial resistance measurements. Changes to the thickness and composition of the coatings and oxide layers after single cell tests will also be reported alongside additional insights from correlative characterization approaches like atomic force microscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Overall, these findings will help steer the development of PTL treatments and coatings for highly durable and efficient PEM water electrolyzers towards meeting the U.S. Department of Energy’s Hydrogen Shot to reduce the cost of clean hydrogen production to $1 per kg by 2031.
Funding for this work was provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office through the H2NEW Consortium. Electron microscopy research conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.
In Situ Vs. Ex Situ Degradation Studies of IrO2-Based Porous Catalysts for Proton Exchange Membrane Water Electrolysis
Authors: Duran Silvia , Faustini Marco , Grimaud Alexis , Peron Jennifer 
Published: September 2023

Regardless of the promising performances of Proton Exchange Membrane Water Electrolyzers (PEMWE) for H2 production, the high overpotential towards the oxygen evolution reaction (OER) (slow kinetic) still limits the large-scale use of such devices. 1,2

We have recently extended the aerosol synthesis route, a green, cheap and scalable synthesis technique, to the preparation of highly porous noble-metal pure and mixed oxides to optimize the electrocatalytic activity of the anode catalyst.2,3In this work, we are taking the advantage of the versatility of this process to prepare a large panel of iridium oxides with similar morphology and composition but different crystallinity and surface states and therefore different electrochemical properties.
By combining in situ (electrolyzer) and ex situ (three-electrode cell) electrochemical studies on these materials, this work aims at understanding the physico-chemical characteristics-stability relationships of iridium oxides as well as establishing a correlation between ex situ and in situ ageing experiments. Stress tests with different upper potentials limits are performed both in electrolyzer and RDE configurations to evaluate the stability of these materials, and the amount of iridium dissolved by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Beside chemical degradation, the unique morphology of these materials is particularly well-suited for following the morphological changes occurring upon ageing by Scanning Electron Microscopy (SEM).2,3 This study will help to improve the understanding of RDEs and PEMWEs testing behavior upon OER with the aim to correlate these two approaches using current metrics i.e., S-number 4, but also to elaborate or redesign efficient catalysts.

References

[1] A.S. Aricò et al.
J. Appl. Electrochem
., 2013. doi:10.1007/s10800-012-0490-5.
[2] M. Faustini et al.
Adv. Energy Mater
., 9 (2019), 1-11. doi :10.1002/aenm.201802136
[3] M. Elmaalouf et al.
Nat. Commun
., 12 (2021), 3935. doi : 10.1038/s41467-021-24181-x
[4] S. Geiger et al.
Nat. Catal
., 1 (2018), 508-515. doi: 10.1038/s41929-018-0085-6

Figure 1
(Invited) A Critical Review on the Expressions of Energy Efficiency Used in Low Temperature Water Electrolysis
Authors: Lamy Claude 
Published: September 2023

The accurate knowledge of the energy efficiency coefficient of low temperature water electrolysis (Alkaline, PEM or AEM Electrolyzer) is a critical-point to estimate the total cost of electrolytic hydrogen production. After describing the fundamentals of these three processes and presenting the main data of water electro-dissociation under given temperature and pressure conditions, the energy efficiency coefficient can be calculated at the Laboratory scale by taking the ratio of the theoretical energy (ΔH) to decompose water under equilibrium conditions (no current) to the real energy used (ΔH + energy losses) to electrolyze water at a given current intensity. Different approximations of this coefficient are discussed and compared to data from literature. Conversely in the industry this coefficient can be calculated by taking the ratio of the total energy of hydrogen collected at the exhaust of the electrolyzer to the total energy (electricity + heat) supplied to the complete system. It is demonstrated that both definitions are consistent and similar if all the energy involved is taken into account. It is also shown that some approximations, in particular those neglecting the thermal energy in the denominator of this ratio, give efficiency coefficients larger than unity for cell voltages lower than the thermo-neutral voltage, which is a thermodynamic non-sense.
The next figure shows the plot of the theoretical energy efficiency coefficient ε

cell
for p = 1 bar under the STP conditions (U0
tn
= 1.48 V and U
0

rev
= 1.23 V) up to Ucell

= 2.0 V. There is a continuous decrease of ε

cell,th
vs. Ucell
from 1.0 to 0.85 when Ucell
= Utn
= 1.48 V under STP conditions.

Figure 1
Autonomous Materials Synthesis Strategies Towards Accelerated Discovery of Novel Functional Nanomaterials for Green Energy Production
Authors: Abdelhafiz Ali 
Published: September 2023

Electrocatalysts designed by alloying two or more elements (e.g., transition metals) showed promising enhancement in catalytic activity and durability due to synergistic effects from alloying, such as strain engineering or electron exchange. The potential of the alloying approach is constrained by standard synthesis methods (e.g., wet chemistry and thermal decomposition techniques) due to the governing thermodynamics rules (e.g., miscibility of the different alloying elements). That renders the synthesis of high entropy alloys (HEA), with more than 3 elements, to be complicated and tedious to achieve by those conventional methods.
In the presented talk we are presenting different strategies to synthesize metastable high entropy alloys (HEA) and their outstanding catalytic performance towards OER, in correlation to their unique chemistries and structures. Rapid cycling of temperature from room 25 °C to highly elevated levels (1700 °C), in conjunction with ultra-rapid cooling, within milli-second range have been demonstrated by different methods including rapid Joule heating, Intense light flashing, and microwave plasma shock. Our results show successful synthesis of non-noble metals HEA NPs, possessing higher catalytic activity than IrO2 catalyst for OER. The nature of the alloying elements dictates OER activity by promoting different oxidation states of the catalytically active transition metals (e.g., Fe, Ni and Co). In addition, a phenomenal in-situ chemical welding of HEA NP to carbon support, yielded HEA catalysts with two orders of magnitude longer durability than IrO2. Our developed techniques resulted in formation of super-strong metal-carbide bonds “chemically welding” HEA NP to the catalyst support.
Synthesis of various HEA catalyst and their electrocatalytic performance screening has been carried out by using liquid handler robots and multi-axes robotic arm systems. Moreover, to optimize the design of materials (structure and chemistry), we are using active learning techniques to evaluate the achieved performance results by applying Gaussian process, followed by applying Bayesian Optimization techniques to propose novel chemistries and structures with a higher probability to achieve further improved performances. The presented the study does not open the door only towards developing novel catalysts for energy production. However, it presents a strategy with multiple successfully demonstrated platforms towards accelerated discovery of novel materials. The high-throughput nature of the synthesis protocols presented in this talk can produce tens of thousands of different novel chemistries, at the same time taken by conventional methods to synthesize just a few, at a minimal energy consumption, cost, and manpower.