bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Ionomer-Free Porous-Transport Electrode Design for Proton-Exchange-Membrane Water Electrolysis
Authors: Lee Jason Keonhag , Anderson Grace , Mukundan Rangachary , Weber Adam Z. , Peng Xiong 
Published: August 2024

Clean hydrogen, which is set to reduce the carbon footprint for hard-to-decarbonize sectors, relies on large-scale deployment of water-electrolysis technologies, particularly proton-exchange-membrane water electrolyzers (PEMWEs). However, as iridium-based electrocatalysts remain the only option for PEMWEs, its low abundance is likely to become the bottleneck for a sustainable hydrogen economy. Therefore, developing PEMWEs at low iridium loading is an urgent task. Herein, we propose a high-performing and durable ionomer-free porous transport electrode (Ir PTE) that is fabricated using a facile physical vapor deposition method. This fabrication method creates a thin layer of nanosized iridium catalyst that is well attached to the porous transport layer surface. The proposed Ir PTE at ~ 0.1 mgIr/cm2 demonstrates voltage reduction of > 600 mV compared to the traditionally coated PTE at 1.8 A/cm2, and cell voltage degradation of only 29 mV at average rate of 0.58 mV/1000-cycles after 50k cycles of accelerated-stress tests at 4 A/cm2.1 By further designing nano-channel features of the ionomer-free PTE, we demonstrate expedited localized transport features that allow durable operation of PEMWE for over 2000h with degradation rate of 11.7 µV h-1. Moreover, the ionomer-free feature of Ir PTE enables facile recycling of multiple components of PEMWEs, which is critical to enable circular clean hydrogen economy.
Reference:

Lee, J. K. et al. Ionomer-free and recyclable porous-transport electrode for high-performing proton-exchange-membrane water electrolysis. Nat. Commun.
14, 1–11 (2023).
Application of Hipims Coatings to Enhance the Durability and Performance of Structural Components of PEM Electrolyzer Anodes
Authors: Santiago Varela Jose Antonio Antonio , Fernandez Ivan , Diaz Rodriguez Pablo , Wennberg Ambiorn , Panizo Miguel 
Published: August 2024

Porous transport layers (PTL) and bipolar plates (BPP) are structural elements that transport water, gases, electrons as well as heat within the electrolysis cells. On the anode side, the state-of-the-art material for BPP and PTL is titanium due its higher corrosion resistance under the operating conditions of electrolysis (high electrochemical potential, acidic and oxidizing environment) compared to other materials [1]. However, titanium components tend to form an oxide layer that rises the interfacial contact resistance (ICR) and leads to a poor performance since metal oxides are semiconductors or insulators. This issue is usually addressed by applying precious metal coatings, such as platinum or gold. In this work, we present the potential of high power sputtering techniques (HiPIMS) to manufacture ultra-low loading Pt coatings (<20 nm) with good homogeneity and high performance at an industrial scale. The influence of HiPIMS parameters on coating-substrate interface, as well as the coating properties have been evaluated. SEM, AFM and HRTEM microscopy have been used to evaluate the coating thickness and morphology. XRD analysis has been carried out to evaluate the influence of the HiPIMS parameters on the growth mode of Pt coatings, tailoring the coating texture from [200] to [111]. HiPIMS technique also provide enhanced density compared with other coating techniques due to the higher ionization achieved in the plasma [2]. The deposition of denser and defect-free coatings by HiPIMS enables the application of stainless steel components. HiPIMS prevents the formation of columnar structures and reduces oxygen diffusion. In this work, Nb- and Ti-based protective coatings have been deposited by HiPIMS on stainless steel 316L. A comparative between coated Ti Gr2 and SS316L has been set, showing the potential to reduce costs in the next generation of PEMWE structural components.
References:

[1] P. Shirvanian and F. van Berkel, Electrochemistry Communications 114 (2020) 106704

[2] K. Sarakinos et al., Surface & Coatings Technology 204 (2010) 1661–1684
Optimization of Transport Components and Electrode Interfaces for Low Iridium Oxide Loading PEM Electrolysis
Authors: Lang Jack Todd , Fortiner Serafina , Ouimet Ryan J. , Kulkarni Devashish , Glenn Jennifer , Capuano Christopher B. , Erb Bryan , Smeltz Andrew , Zenyuk Iryna 
Published: August 2024

Moving towards lower iridium oxide (IrOx) catalyst loadings for the anode side of polymer electrolyte membrane water electrolyzers (PEMWE) requires tuning of the catalyst layer-porous transport layer (PTL) interface. To see widespread deployment, PEMWE anodes need to lower the loadings from 1-2 mg/cm2 IrOx down to 0.1 mg/cm2 [1]. The catalyst layer can become less uniform and more disconnected at these lower loadings, so the addition and optimization of a microporous layer (MPL) onto the PTL to improve interfacial contact and in-plane connectivity is essential to move toward the more sustainable lower loadings [2]. First, a set of PTLs with MPLs are made such that morphological properties are varied between them. Then, the PTLs with MPLs are combined with anode catalyst layers with IrOx loadings of 0.7, 0.5, 0.3, and 0.1 mg/cm2 to create cells to record polarization curves, stability tests, and catalyst degradation rates. The morphology of the PTLs and MPLs is quantified using X-ray computed tomography (CT). The important morphological characteristics that can be varied and measured with X-ray CT include porosity, pore size distribution, tortuosity, and thickness for each the MPL and base PTL. Using operando X-ray CT and radiography, oxygen transport through the PTL and channel can be observed to provide further information to the performance of the novel PTLs and MPLs. By using a two-dimensional continuum PEMWE model, insights into the effects on the cell performance and the contact resistance present at the MPL-catalyst layer brought about from PTL and MPL morphology alterations can be extracted to help guide the optimization efforts. Through combining these results, an optimal set of manufacturing/morphological parameters can be found to tune PTL and MPL production for the low-loaded catalyst layers that are needed for the future of PEMWEs.
References:
[1] M. Clapp, C. M. Zalitis, and M. Ryan, “Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis,” Catalysis Today, vol. 420, p. 114140, 2023. doi:10.1016/j.cattod.2023.114140
[2] M. Bernt, A. Siebel, and H. A. Gasteiger, “Analysis of voltage losses in PEM water electrolyzers with low platinum group metal loadings,” Journal of The Electrochemical Society, vol. 165, no. 5, 2018. doi:10.1149/2.0641805jes
Oxygen-Deficient Thermal Treatment Boosts Performance of Co-Ni-Fe Oxide Electrocatalyst in Oxygen Evolution Reaction
Authors: Pham Trang Minh , Hnat Jaromir , Surkus Annette-Enrica , Francke Robert 
Published: August 2024

The production of green hydrogen through water electrolysis using electricity generated from renewable sources is one of the most promising strategies toward achieving a carbon-neutral economy.[1-3] Water electrolysis is an effective and well-established water splitting process consisting of two half-cell reactions, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at cathode and anode, respectively. Although hydrogen as the value-added product is generated at the cathode, the anodic reaction plays an important role in determining the reaction kinetics of the entire water splitting process due to the multiple-electron transfer.[4] Therefore, developing low-cost and highly active OER electrocatalysts is one of the keys to further improve overall efficiency of water electrolysis. Among various water electrolysis technologies, alkaline water electrolysis (AWE) has been commercialized for many decades and standing for medium-scale hydrogen production and using non-noble metals as electrocatalysts.[5]
Co-, Ni-, and Fe- oxides or (oxy)hydroxides are reported as auspicious OER electrocatalysts for AWE, as well as abundance on earth.[6] In addition, oxygen vacancies in metallic oxides are reported recently as an effective approach to enhance catalyst activity for OER.[7] Herein, we present trimetallic oxides (CoNiFe oxides) annealed in different atmospheres which are oxygen-rich (A; air), an oxygen-poor (M; 1 vol% air in argon), and oxygen-free (H; 5 vol% H2 in argon), respectively, The CoNiFe (2:2:1)/M with a molar ratio of Co : Ni : Fe = 2 : 2 : 1 treated under an oxygen-poor atmosphere (M) exhibits the best performance in 1 M KOH, with an overpotential of 291 mV at 10 mA cm-2
geo, a mass activity at 1.56 V versus the reversible hydrogen electrode (RHE) of ~345 A g-1
catalyst, and a small Tafel slope of 32.0 mV dec-1. Moreover, CoNiFe (2:2:1)/M shows excellent stability in the OER process for at least 50 hours at 100 mA cm-2
geo at lab scale and ~75 h at 400 mA cm-2 in an alkaline electrolyzer. This work presents a simple and effective method to design OER catalysts based on trimetallic oxides with oxygen deficiencies for alkaline water electrolysis.
References:
[1] T. Yusaf, M. Laimon, W. Alrefae, K. Kadirgama, D. Ramasamy, M. Kamal and B. Yousif, Appl. Sci., 2022, 12, 17.
[2] M. Neuwirth, T. Fleiter, P. Manz and R. Hofmann, Energy Convers. Manag., 2022, 252, 115052.
[3] H. L. S. Shiva Kumar, Energy Rep., 2022, 8, 21.
[4] Q. Liang, G. Brocks and A. Bieberle-Hütter, JPhys Energy, 2021, 3, 026001.
[5] Y. D. Zi-You Yu, Xing-Yu Feng, Xingxing Yu, Min-Rui Gao and Shu-Hong Yu, Adv. Mater., 2021, 33.
[6] M. Yu, E. Budiyanto and H. Tüysüz, Angew. Chem. Int. Ed., 2022, 61, e202103824.
[7] K. Zhu, F. Shi, X. Zhu and W. Yang, Nano Energy, 2020, 73, 104761.
Research and Development Needs to Enable Renewable-Powered Liquid Alkaline Electrolyzers
Authors: Lindquist Grace 
Published: August 2024

Low temperature electrolysis (LTE) is the most promising method for fully renewable hydrogen production. However, to compete with current hydrogen production methods (which produce CO2), substantial cost reductions and efficiency improvements are necessary. Of the various LTE technologies, liquid alkaline (LA) electrolysis is the most mature. It has proven large scalability and can operate with all earth-abundant materials. However, most conventional LA electrolyzers are limited to lower current density operation than newer LTE technologies.
Most LA electrolyzers operate with uncatalyzed Ni anodes, despite the existence of many highly active catalysts for oxygen evolution in alkaline conditions. This is because catalyzed systems require constant operation, as the catalyst layers degrade and delaminate rapidly upon exposure to the reverse polarization conditions experienced during system shutdown. This limitation prevents the integration of catalyzed electrodes, as even a single unexpected plant shutdown causes significant efficiency and cost losses. Further, this prevents fully catalyzed LA electrolyzers from directly operating with renewable power sources with large power fluctuations. Therefore, the development of reverse-current tolerant catalyst layers is essential to enable high-efficiency renewable energy powered LA electrolyzers.
This talk will detail the mechanisms of electrode degradation during electrolyzer system shutdown. Our findings reveal anode catalyst layers fail through a combined electrochemical and mechanical degradation mechanism. I will discuss key differences in the cathode versus anode operating environments that explain the difference in reverse current tolerance. Considering these results, I will highlight priority research and development directions for developing anode and cathode catalysts for renewable-powered LA electrolyzers.
Electrolyte-Induced Fe-Doping of LaNiO3 Model Surfaces for Water Electrolysis
Authors: Le Phu Tran Phong , Sturm Jacobus Marko , Koster Gertjan , Bieberle-Hütter Anja , Baeumer Christoph 
Published: August 2024

Renewable energy needs to be store in different energy forms for the energy transition away from fossil fuels. One of most promising forms is chemicals such as H2 and C-based fuels obtained via electrochemical reactions. The common hinderance in such reactions is the sluggish oxygen evolution reaction (OER), which causes low energy efficiency in conversion devices. Developing highly active, earth-abundant OER electrocatalysts in alkaline media is necessary to boost the performance of such devices. Fe ion content in electrolyte is known to influence the OER-activity of metal oxide electrocatalysts. For example, the Fe incorporation in NiOOH is a well-established and important effect for OER.[1] Here, we present the effect of absorbed Fe on the OER activity of the epitaxial Ni-surface terminated LaNiO3 thin films. The correlation between surface species and OER activity of electrocatalysts was investigated using surface-sensitive low-energy ion scattering and X-ray photoemission spectroscopies. We observe more than an order-of-magnitude boost in OER activity during initial cycling, from 0.15 mAcm-2 to 3.40 mAcm-2 at 1.60 V vs. reversible hydrogen electrode. The activity increase was mainly caused by the incorporation of up to 5 % Fe at the top surface of LaNiO3 film (less than ~1 nm) even though only a very trace amount of Fe ion, 30 ppb, is present in the 0.1 M electrolyte of high purity KOH 99.99 %. Our results demonstrate that the disordered active surface phase, which develops even on single crystalline surfaces, is a complex interplay between the as-prepared (surface) crystalline structure, composition of the solid electrocatalyst and the liquid electrolyte, and has strong impact on the final OER activity, implying that we need to think differently about the crystalline electrocatalysts: crystalline bulk and dynamically changing surface layer.
[1] L. Trotochaud, S.L. Young, J.K. Ranney, S.W. Boettcher, Nickel–Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation, J. Am. Chem. Soc. 136 (2014) 6744–6753.
Zero-Gap Liquid Alkaline Water Electrolyzers: Challenges in Benchmarking and Directions for Development
Authors: Leonard Daniel , Maurya Sandip , Chavez Luis A , Ybarra Rigobert 
Published: August 2024

Green hydrogen is expected to play a central role in the replacement of fossil energy sources, especially in difficult to decarbonize sectors of the economy. Currently, low temperature methods of electrolysis are the only commercially realized sources of green hydrogen. Liquid alkaline water electrolysis (LAWE) is the most widely utilized method of electrolysis, with a 100-year history of use. Given this lengthy history one could be forgiven for assuming that there is little development left. However, standard LAWE materials and cell designs do not achieve the production, efficiencies, and durability necessary to meet the anticipated demand for green hydrogen.
To spur development in this neglected area of hydrogen production, the US Department of Energy, Hydrogen and Fuel Cell Technology Office (DOE-HFTO) added LAWE to its Hydrogen from Next-generation Electrolyzers of Water (H2NEW) Consortium. One of the main tasks for this part of the consortium is to benchmark and validate materials and cell components for LAWE. This includes the development of lab-scale cell hardware and test protocols that can be widely disseminated in the research community. The result of this work will be the development of the methods and materials necessary to achieve robust and reproducible datasets for the improvement of catalysts, separators, cell architecture and operation.
We will present the status of the benchmarking effort. This will include a description and explanation of a lab-scale LAWE test station, electrolyte handling, and hydrogen safety. The requirements for the safe operation of an electolyzer using high concentration alkaline electrolytes differs significantly from more typical proton exchange, or anion exchange membrane systems. We will also discuss common sources of error that can significantly influence cell performance and result in poor reproducibility.

Acknowledgement:
This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.
The Experimental Determination of the HOR/HER Activity on Platinum and the pH-, Cation-, and Other Effects (Part 2)
Authors: Brandes Benedikt Axel , Chatzichristodoulou Christodoulos 
Published: August 2024

Due to frequent inconsistencies in determining the HOR/HER activity on Pt(pc) we present one of the most extensive datasets on this reaction, ranging over the entire pH scale, various cations and anions, and concentrations, using the common RDE method. Here we explain why the Koutecký-Levich equation must not be used to determine the exchange current density in the micropolarization region, and that pH-buffers may be avoided.
We clarify the anticipated pH dependency on account of the reaction mechanism, how this is influenced by mass transport limitations in most of the pH range, discuss the origin of activity reduction at high pH values, and provide new insights into the H-upd regions.

Figure 1
(Invited) Photocatalytic H2 Evolution Activity of Anisotropic-Shaped ZnSe-AgInSe2 Solid Solution Quantum Dots with a Near-IR-Responsivity
Authors: Torimoto Tsukasa , Masuoka Ko , Akiyoshi Kazutaka , Uematsu Taro , Kuwabata Susumu , Kameyama Tatsuya 
Published: August 2024

Semiconductor nanocrystals, often referred to as quantum dots (QDs), exhibit unique physicochemical properties due to the quantum size effect when their size is less than 10 nm. In our previous works, we successfully synthesized Zn-Ag-In-S (ZAIS) solid solution QDs with a tunable energy gap (Eg) and then reported the photocatalytic activity for H2 evolution depending on their morphology and particle composition [1,2]. However, ZAIS QDs have limited light absorption with wavelengths less than ca. 600 nm, restricting their utilization of near-infrared light in solar light. In this study, we report the preparation of near-IR-responsive QD photocatalysts with use of Zn-Ag-In-Se (ZAISe) solid solution semiconductors. Precise controls over their morphology and particle composition enabled to vary their photocatalytic H2 evolution activity.
ZAISe QDs with different compositions and particle shapes (sphere or rod) were synthesized by thermal decomposition of corresponding metal acetates and selenourea in a mixture solution of oleylamine and dodecane thiol at 250 oC. The chemical composition of QDs was controlled by varying the Zn fraction in metal precursors, ensuring nearly stoichiometric composition.
The obtained QDs with a rod shape had lengths varying from ca. 10 to 100 nm, correlating with an increase in the Zn fraction. The onset wavelengths of absorption spectra of the ZAISe QDs were red-shifted from 500 nm to 900 nm with decreasing Zn fraction, indicating that the Eg of ZAISe QDs was controlled between visible and near-infrared wavelength regions.
The QDs modified with dodecane thiol showed poor dispersibility in water and almost no photocatalytic activity for H2 evolution. In contrast, the surface modification of QDs with 3-mercaptopropionic acid enabled to uniformly disperse in an aqueous solution. The photocatalytic activity of ZAISe QDs was investigated for H2 evolution as a model reaction. The irradiation to ZAISe QDs in an aqueous solution containing Na2S and Na2SO3 as hole scavengers was carried out using Xe lamp light (λ> 350 nm). The H2 evolution rate exhibited a remarkable dependence on both the composition and particle shape of ZAISe QDs. The photocatalytic activity showed a tendency to increase with the enlargement of the Eg of QDs, probably due to the negative shift of conduction band minimum potential. The optimum H2 evolution activity was obtained with rod-shaped QDs having the Eg of 1.65 eV, being twice as large as that of spherical QDs with a similar Eg. This behavior can be attributed to the change of the crystal facets exposed on the QD surface.

References

Kameyama, T. Takahashi, T. Machida, Y. Kamiya, T. Yamamoto, S. Kuwabata, and T. Torimoto, J. Phys. Chem. C, 2015, 119, 24740-24749.

Torimoto, Y. Kamiya, T. Kameyama, H. Nishi, T. Uematsu, S. Kuwabata, and T. Shibayama, ACS Appl. Mater. Interfaces
2016
, 8, 27151-27161.
(Invited) Designing Plasmonic Photocatalysts
Authors: Cortes Emiliano 
Published: August 2024

Nanostructured surfaces and colloids with designed optical functionalities - such as plasmonic and photonic nano and metamaterials - allow efficient harvesting of light at the nanoscale. Exploiting light-driven matter excitations in these artificial materials opens up a new dimension in the conversion and management of energy at the nanoscale [1-4]. One example are plasmonic and photonic catalysts, that can indeed confine solar energy into molecular regions [4-11].
In this talk, I will present our recent efforts in order to understand the intricate realm of losses in plasmonic nanoparticles by studying this issue at the single-particle level. I will present a series of studies trying to correlate plasmonic photocatalytic activity with reactivity, temperature and field at the nanoscale. Our fundamental understanding of light-matter interaction in these systems can hopefully contribute to the rational design of future nanocatalysts; influencing diverse applications such as photocatalysis and temperature management, among others [1-11].

References

[1] E. Cortés, Nature 614, 230-232 (2023)
[2] E. Cortés, et al. Nature Rev. Chem., 6, 259–274 (2022)
[3] E. Cortés, et al. Chem. Rev. 122, 15082–76 (2022)
[4] S. Ezendam, et al. ACS Energy Letters, 7, 778-815 (2022)
[5] M. Herran, et al. Adv. Funct. Mat., 2203418 (2022)
[6] J. Gargiulo, et al. Nature Communications 14, 3813 (2023)
[7] L. Nan, et al. Nano Letters 23 (7), 2883–2889 (2023)
[8] A. Stefancu, et al. ACS Nano 17 (3), 3119–3127 (2023)
[9] L. Hüttenhofer, et al., Adv. Energy Mat., 46, 2102877 (2021)
[10] M. Herran, et al. Nature Catalysis, accepted (2023)
[11] S. Ezendam, et al. ACS Nano, accepted (2023)
Proton Activity and Pathway in Aqueous Organic Redox Flow Battery Electrolyte
Authors: Wang Wei 
Published: August 2024

Aqueous soluble organic (ASO) redox-active materials have recently shown great promise as alternatives to transition metal ions employed as energy-bearing active materials in redox flow batteries for large-scale energy storage because of their structural tunability, cost-effectiveness, availability, and safety features. However, development so far has been limited to a small palette of organics that are aqueous soluble. This presentation will use fluorenone as an example to showcase how a natively redox-inactive molecule can be tuned to possess two-electron redox reversibility through hydrogenation and dehydrogenation. The modified fluorenone molecules demonstrated high energy density and recorded stable cycling. Furthermore, research has shown the unique chemical-electrochemical coupled redox reactions mechanism; thus, the system rate capabilities can be improved by incorporating suitable hydrogen acceptors that regulate the proton pathway for faster kinetics.
Reference:
Feng et al., Science 372, 836–840, 2021
Feng et al., Joule 7, 1–14, 2023