bluuebunny/crossref_metadata_2025 huggingface dataset:
Photophore-Anchored Molecular Switch for High-Performance Nonvolatile Organic Memory Transistor
Authors: Hassan Syed Zahid , Kwon Jieun , Lee Juhyeok , Sim Hye Ryun , An Sanghyeok , Lee Sangjun , Chung Dae Sung
Published: December 2024

Over the last decade, there has been a marked increase in interest in memory devices embedded with molecular switches, especially field-effect transistors (FETs). These molecular switches are integrated to regulate the resistance or current levels within FETs. Despite significant efforts, achieving a large memory window with extended retention time remains challenging. This difficulty arises because the isomeric state of a molecular switch cannot function as a stable deep trap state in the semiconductor layer. This study addresses this issue by introducing chemical bonding between the molecular switch and the conjugated polymeric semiconductor. This bonding enables the closed isomer of diarylethene (DAE) to act as a morphologically stable deep trap state. Azide- and diazirine-anchored DAEs are synthesized to form chemical bonds with the polymer through photocrosslinking, thus creating permanent and controllable trapping states near the conjugated backbone of the polymer semiconductor. As a result, when diazirine-anchored DAE is blended with F8T2 and subjected to photocrosslinking, the resulting organic FETs demonstrate impressive memory performance, including a memory window of 22 V with a retention time exceeding 106 seconds, a high photoprogrammable on/off ratio greater than 103, and high operational stability over more than 100 photocycles. Additionally, photophore-anchored DAEs allow for precise patterning, which enables meticulous control over the semiconductor layer structure.

Figure 1
Development of High Durable Catalyst for PEFC
Authors: Akiyama Tomohiro , Kagawa Masaru , Matsutani Koichi
Published: December 2024

PEFC is focused as highly efficiency and clean energy device to reduce emission of CO2. Pt/C and PtCo/C are widely used as cathode electrocatalyst for PEFC. But there are many issues required for catalyst such as low platinum and high durability for the widespread use of PEFC. We tried to improve catalyst durability against potential cycles attributed to Pt dissolution. We prepared barrier layer on the Pt/C cathode catalyst surface to prevent the increasing in particle size due to Pt dissolution and reprecipitation.

The ORR mass activity at 0.90V and electrochemical surface area (ECSA) of catalysts were measured by 25cm2-MEA. Durability evaluation was carried out by conducting potential cycles of 650mV-1050mV attributed to Pt dissolution and measuring the activity every constant potential cycles. Fig.1 shows mass activity and ECSA of standard Pt/C and improved Pt/C catalyst with potential cycles. ORR mass activity and ECSA of Pt/C catalyst was significantly decreased after cycles. It seems that the dissolution of Pt remarkably progressed. On the other hand, decreasing in mass activity and ECSA of improved-Pt/C catalyst with barrier layer was significantly suppressed compared to Pt/C catalyst. It was shown that decreasing in surface area due to dissolution and reprecipitation of Pt would be prevented and high activity was maintained even after potential cycles by barrier layer.

To understand Pt dissolution phenomenon of each catalysts, we investigated the MEA after the durability test by TEM and EPMA analysis. From analysis results, increasing in particle size and Pt band formation of improved Pt/C catalyst were significantly suppressed after durability test compared to standard Pt/C catalyst. These results suggest that barrier layer on the catalyst surface is much effective for improving catalyst durability against potential cycles.

Figure 1
Carbon Interaction with Precious Metal Catalysts for ORR : More Than a Support
Authors: Roiron Camille , Ferro Giovanni , Chen Jiazhe Loki , Cosenza Alessio , Atanassov Plamen
Published: December 2024

Proton exchange membrane fuel cells (PEMFC) are developed to lower the carbon footprint of the medium- and heavy-duty vehicles. To this day, the durability of the PEMFC catalysts, especially for the kinetically sluggish oxygen reduction reaction (ORR) that occurs at the cathode, remains a significant obstacle. Current state-of-the-art electrocatalysts are comprised of platinum-based nanoparticles anchored on high surface area carbon black supports (Pt/C). To prevent the catalyst degradation and meet the U.S. Department of Energy’s near-term activity benchmarks [1], employment of mesoporous carbon supports is considered. However, to understand how porosity affects the catalyst durability, model catalysts must be studied [2].

Here, we systematically investigate the effect of carbon support micro- and mesoporosity, chemical structure and position of the active nanoparticles on the support. Pt/C electrocatalysts are synthesized by decorating different carbon materials with spherical Pt nanoparticles. We developed a methodology to place the Pt nanoparticles at will inside or outside the carbon mesopores; this was done for several carbon supports, while keeping constant the particle size and crystallinity. The electrochemically active surface area (ECSA) and intrinsic activity are evaluated in liquid electrolyte rotating ring disk electrode (RDE). We demonstrate that the carbon chemical structure significantly affects the exposure of Pt surface and the catalyst performance. More specifically, two materials with very similar Pt loadings (based on thermogravimetric analysis), particle size distributions and XRD patterns demonstrate very different electrochemical behavior. ECSA and mass activity variation of 59 m2/gPt and 241 A/gPt (at 0.9 VRHE) respectively are obtained between the two catalysts. This stark difference highlights that carbon support effects should be studied in isolation from all other parameters and that their influence cannot be neglected when studying the effect of Pt locality and chemical modifications.

The controlled locality of Pt nanoparticles inside or outside the carbon mesopores provides us with a pathway to investigate how the metal and support interact. Leveraging this relationship we determine if surface modifications of the supports can tune Pt-carbon interactions to promote activity and durability for the next generation catalysts.

[1] M. Rezaei Talarposhti, T. Asset, S. T. Garcia, Y. Chen, S. Herrera, S. Dai, E. J. Peterson, K. Artyushkova, I. Zenyuk, P. Atanassov, ChemPhysChem, 21 (2020) 1331-1339.

[2] G.S. Harzer, A. Orfanidi, H. El-Sayed, P. Madkikar, H.A. Gasteiger, J. Electrochem. Soc. 165 (2018) F770-F779.
Atomic Ordering Promoted L10-Zn-PtCo Intermetallic Nanocatalysts for Enhanced Oxygen Reduction Reaction in PEMFCs
Authors: Chang HyunWoo , Ryu Jae Hyun , Lee KwangHo , Roh JeongHan , Lee SangJae , Bak Junu , Shin Dongwon , Kim Minjun , Yang HyunWoo , Lee Wonbo , Cho EunAe
Published: December 2024

The sluggish oxygen reduction reaction (ORR) kinetics has inhibited the widespread commercialization of polymer electrolyte membrane fuel cells (PEMFCs). Therefore, there has been a great need for catalysts that promote the ORR. PtCo intermetallic nanoparticles supported on conductive carbon, which have superior activity and durability toward the ORR, have been considered promising catalysts for the cathode in PEMFCs. In general, high-temperature annealing is required to synthesize intermetallic catalysts, which accompanies the sintering of the nanoparticles, leading to a decrease in electrochemical active surface area (ECSA). Therefore, a sophisticated strategy is required to enhance the ordering degree of PtCo intermetallic compound nanoparticles without making the annealing process extreme. Here, we present L10-Zn-PtCo intermetallic nanocatalysts (Zn-PtCo/Zn-NC) in which the Zn incorporation strategy enhances the ordering degree. Computational calculation using machine learning force field (MLFF) elucidates that introducing Zn atoms can promote diffusion kinetics within the crystal structure of PtCo. X-ray diffraction (XRD) patterns and extended X-ray absorption fine structure (EXAFS) quantitatively confirm the enhancement of the ordering degree due to incorporating Zn atoms. In the half-cell configuration, the synthesized Zn-PtCo/Zn-NC catalyst shows an initial mass activity of 1.76 A mgPt
-1 at 0.9 VRHE. In addition, it maintains 93.8% of its initial ECSA after the accelerated durability test (ADT). In H2-Air fuel cells, the Zn-PtCo/Zn-NC cathode achieves a high peak power density of 0.64 W cm-2, compared to that of the Pt/C (0.50 W cm-2), even with a low Pt usage of 0.05 mgPt cm-2 at the cathode.
Novel Mesoporous Carbon Supporting PGM As an Effective ORR Catalyst in PEM Fuel Cells
Authors: Liu Qiao , Wang Xiaojing , Spendelow Jacob S.
Published: December 2024

Polymer electrolyte membrane (PEM) fuel cells convert the chemical energy of hydrogen and oxygen into electrical energy through a proton-conducting polymer membrane. These cells are highly valued in compact applications such as electric vehicles and portable power systems for their high power density and low operating temperatures. The catalyst support plays a crucial role, not only anchoring the catalyst nanoparticles but also enhancing Oxygen Reduction Reaction (ORR) activity through heteroatom doping, facilitating mass transfer via microchannels, and improving conductivity.1 Mesoporous carbon, merging electrochemical and high surface area properties, serves as an ideal catalyst support. Its mesoscopic structures enable high dispersion of electrocatalysts, and although mesopores contribute relatively less to surface area compared to micropores, they are more effective for mass transport. 2-3

We employ Metal Organic Frameworks (MOFs)-derived porous carbon, synthesized through pyrolysis, to provide structurally optimized mesoporous support that enhances surface area and electrochemical stability. MIL-101 is a highly porous, crystalline MOF known for its exceptional surface area and potential in gas storage, separation, and catalysis.4 Our research details the production of a series of mesoporous carbon C-X-MIL-101 (X = NH2, CH3, NO2, OMe) through carbonization of X-MIL-101 MOFs at 1100 °C followed by acid etching to remove residual aluminum oxides, resulting in high-surface-area, controlled-mesoporosity carbon materials. Platinum nanoparticles are subsequently embedded using a solvent impregnation method to produce Pt@C-X-MIL-101, optimizing platinum use and preventing surface deposition. The resulting Pt@C-X-MIL-101 catalysts have been tested in fuel cell and comprehensive findings will be presented at the conference.

Zaman, S., Wang, M., Liu, H., Sun, F., Yu, Y., Shui, J., ... & Wang, H. (2022). Trends in Chemistry, 4(10), 886-906.

Chang, H., Joo, S. H., & Pak, C. (2007). Journal of Materials Chemistry, 17(30), 3078-3088.

Xu, J. B., & Zhao, T. S. (2013). RSC Advances, 3(1), 16-24.

Zorainy, M. Y., Alalm, M. G., Kaliaguine, S., & Boffito, D. C. (2021). Journal of Materials Chemistry
A, 9(39), 22159-22217.
Scalable and Tunable Synthesis of Sustainable Nitrogen-Doped Hydrothermal Carbon Materials (N-HTC) As Support Material for Platinum/N-HTC ORR Catalysts
Authors: Martin Julian , Mitrovic Julian , Fischer Anna
Published: December 2024

In electrochemical catalysis, carbon materials play a pivotal role as support material for catalytically active metal nanoparticles, e.g. Pt nanoparticles in case of fuel cells. The physicochemical properties of such carbon supports thereby significantly impact the catalytic activity and stability of thereof derived supported catalysts.

Hydrothermal carbonization (HTC) stands as a thermochemical process utilized in crafting functional carbon materials from biomass or its derivatives. Under elevated temperature and pressure in an aqueous milieu, biomass undergoes conversion into carbonaceous precursors [1].

Presented here is a lab-scale synthesis of nitrogen-doped carbon materials via hydrothermal carbonization, offering versatility as support material for electrocatalysis. The sustainable nitrogen-doped hydrothermal carbon materials (N-HTC) are synthesized from affordable precursors, namely glucose and ovalbumin, at mild temperatures. Subsequent thermal treatment of the resulting carbogels facilitates control over surface chemistry (nitrogen content), porosity, and graphitization/conductivity [2]. Significantly, the synthesis process has been successfully scaled up, while preserving the performance determining parameters of the resulting carbon supports.

Furthermore, these N-HTC materials are impregnated with platinum nanoparticles to create Pt/N-HTC catalysts for oxygen reduction reaction (ORR) in fuel cell applications. Electrochemical techniques are employed to investigate the influence of synthesis conditions, support properties, and nanoparticle characteristics on the ORR activity and stability of the developed catalysts.

References

[1] S. A. Nicolae, H. Au, P. Modugno, H. Luo, A. E. Szego, M. Qiao, L. Li, W. Yin, H. J. Heeres, N. Berge, M.-M. Titirici, Green Chem.
2020, 22, 4747–4800.

[2] J. Martin, J. Melke, C. Njel, A. Schökel, J. Büttner, A. Fischer, ChemElectroChem
2021, 8, 4835–4847.
Science of Scale-up: Electrocatalysts from Lab to Pilot Scale
Authors: Serov Alexey , Lyu Xiang , Yu Haoran , Cullen David A. , Chuahy Flavio
Published: December 2024

Electrocatalysts for several reactions and processes are actively developed and under development by multiple research groups around the globe. These materials include catalysts for Oxygen Reduction Reaction [1], carbon dioxide reduction [2], hydrogen oxidation [3], oxygen evolution [4] and many other classes. While there is a significant interest to these materials both from scientific and industrial point of view a serious question of their scalability and manufacturability had arisen.

In this work aspects of materials scale-up through careful design of reactors, mixing conditions, reaction conditions monitoring and CFD modelling will be reported. A case study on the model system of unsupported silver nanoparticles will be discussed. Silver nanoparticles were synthesized on scale with variation of reagents concentration, different types of impellers and RPM. Materials were characterized by SEM, TEM, XRD, XPS and BET and the data were correlated to the scaleup variables. A CFD model was developed to model nanoparticles formation and was used to guid experimental scaleup effort.

Acknowledgements and Statements.

The authors acknowledge financial support from R2R and H2NEW consortia. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE).

References.

[1] R. Ezhov, O. Maximova, X. Lyu, D. Leshchev, E. Stavitski, A. Serov, Y. Pushkar "Spectroscopic Characterization of Highly Active Fe–N–C Oxygen Reduction Catalysts and Discovery of Strong Interaction with Nafion Ionomer" ACS Applied Energy Materials 7 (2023) 604-613.

[2] Z. Li, P. Wang, X. Lyu, V. Krishna Reddy Kondapalli, S. Xiang, J. D Jimenez, L. Ma, T. Ito, T. Zhang, J. Raj, Y. Fang, Y. Bai, J. Li, A. Serov, V. Shanov, A. I Frenkel, S. D Senanayake, S. Yang, T. P Senftle, J. Wu "Directing CO2 electroreduction pathways for selective C2 product formation using single-site doped copper catalysts" Nature Chemical Engineering 1 (2024) 159-169.

[3] A. Roy, M. R. Talarposhti, S. Normile, I. V. Zenyuk, V. de Andrade, K. Artyushkova, A. Serov, P. Atanassov "Nickel-Copper Supported on Carbon Black Hydrogen Oxidation Catalyst Integrated into Anion-Exchange Membrane Fuel Cell" Sustainable Energy Fuels 2 (10) (2018) 2268-2275.

[4] X. Lyu, Y. Bai, J. Li, R. Tao, J. Yang, A. Serov "Investigation of oxygen evolution reaction with 316 and 304 stainless-steel mesh electrodes in natural seawater electrolysis" J. of Environmental Chemical Engineering 11 (2023) 109667.
High Performance Palladium-Ceria Anodes for Anion Exchange Membrane Fuel Cells
Authors: Bellini Marco , Pagliaro Maria Vincenza , Miller Hamish Andrew , Peruzzolo Tailor , Castello Carolina , Rossi Francesco
Published: December 2024

High-performance anion exchange membranes (AEMs) recently developed for fuel cell (AEMFC) applications has stimulated catalyst developers to synthetize cheaper and more affordable materials in order to accelerate the development of AEMFCs. [1] Cathode catalysts based on not precious metals have been successfully developed (e.g. Fe and Co based cathodes). There are few examples of Pt free anode catalysts. [2] An alternative strategy is the development of high performing catalysts while at the same time reducing as much as possible the critic raw materials loading. We present here a high-performance Pd-CeO2@Cv anode for the hydrogen oxidation reaction (HOR) where an intimate contact between ceria and palladium nanoparticles allows a synergistic effect which improves the anode activity for HOR compared to traditional palladium based anodes (figure 1). [2] Moreover, Pd-CeO2@Cv is a versatile anode, showing high activity toward the oxidation of small and renewable organic molecules in Alkaline Direct Liquid Fuel Cells, such as the oxidation of ethanol and potassium formate. [3
]

Aknowledgements:

The authors acknowledge the FRESH project for funding. (EU, Horizon Europe, HORIZON-RIA-101069605.)

References:

[1] Energy & Environmental Science (2014), 7 (10), 3135-3191

[2] ACS Applied Energy Materials (2019), 2 (7), 4999-5008

[3] Energies (2018), 11 (2), 369

Figure 1: Scheme of the hydrogen oxidation mechanism on Pd-CeO2@Cv

Figure 1
Development of Anode Catalysts for Anion Exchange Membrane Fuel Cells Operating with Both H2 and Liquid Fuels
Authors: Miller Hamish Andrew , Pagliaro Maria Vincenza , Bellini Marco , Peruzzolo Tailor , Castello Carolina , Bartoli Francesco
Published: December 2024

In 2016, for the first time a polymer electrolyte fuel cell with no Pt based electrocatalysts delivered more than 0.5 W cm-2 of peak power density from H2 and air (CO2 free).[1,2] This was achieved with an Ag oxygen reduction (ORR) cathode and a Pd-CeO2 hydrogen oxidation reaction (HOR) anodic electrocatalyst. The hydrogen oxidation (HOR) reaction under alkaline conditions is a kinetically slow process even with Pt group metals. In this presentation, we discuss our strategies to improve the alkaline HOR activity of transition metal nanoparticles. For example, through engineering strong interactions with transition-metal oxides such as CeO2 incorporated in the carbon based catalyst supports.[3] Another strategy involves utilizing novel carbon based supports such as onion like carbon (OLC). The combination of CeO2 and OLC in Pd–CeO2/OLC induces around 7% defects and modifies the electronic structure of the Pd-OLC interface, significantly improving the electrical conductivity due to enhanced charge redistribution, corroborated by density functional theory (DFT) calculations.[4] Alloying of Pd with oxophilic elements like Au and Cu also enhances fuel oxidation reactions by facilitating adsorption of OH- on the catalyst surface. Peak power densities of up to 2 W cm-2 are obtained when Pd-CeO2 is incorporated in AEMFC testing.[5] Regarding liquid fuels, we are currently developing a 100 W fuel cell system using anion exchange membranes and Pd alloy nanoparticle catalysts. The fuel cell stack will be fed with aqueous solutions of potassium formate produced from combining renewable energy and waste industrial CO2. This work is funded by EU Horizon Europe (Project FRESH - GA 101069605) [6].

References

[1] H. A. Miller, A. Lavacchi, F. Vizza, M. Marelli, F. Di Benedetto, F. D. I. Acapito, Y. Paska, M. Page and D. R. Dekel, Angew Chem Int Edit, 55, (2016) 6004.

[2] M. Bellini, M. V. Pagliaro, A. Lenarda, P. Fornasiero, M. Marelli, C. Evangelisti, M. Innocenti, Q. Y. Jia, S. Mukerjee, J. Jankovic, L. Q. Wang, J. R. Varcoe, C. B. Krishnamurthy, I. Grinberg, E. Davydova, D. R. Dekel, H. A. Miller and F. Vizza, ACS Appl Energ Mater, 2, (2019) 4999.

[3] M. V. Pagliaro, M. Bellini, F. Bartoli, J. Filippi, A. Marchionni, C. Castello, W. Oberhauser, L. Poggini, B. Cortigiani, L. Capozzoli, A. Lavacchi, H. A. Miller and F. Vizza, Inorg Chim Acta, (2022) 543.

[4] J. J. Ogada, A. K. Ipadeola, P. V. Mwonga, A. B. Haruna, F. Nichols, S. W. Chen, H. A. Miller, M. V. Pagliaro, F. Vizza, J. R. Varcoe, D. M. Meira, D. M. Wamwangi and K. I. Ozoemena, Acs Catal, 12, (2022) 10938.

[5] H. A. Miller, M. V. Pagliaro, M. Bellini, F. Bartoli, L. Q. Wang, I. Salam, J. R. Varcoe and F. Vizza, ACS Appl Energ Mater, 3, (2020) 10209.

[6] Horizon Europe funded project FRESH, Formate for Renewable Energy Storage, GA 101069605 July 2022 - June 2025.

Figure 1
Active Sites of 3d Transition Metal Oxyhydroxides for OER
Authors: Zhu Jing , Dionigi Fabio , Li Wei-Xue , Greeley Jeffrey , Strasser Peter , Zeng Zhenhua
Published: December 2024

3d transitional metal oxyhydroxides, such as Ni and Co oxyhydroxides with Fe doping, are among the most active and most studied OER catalysts in alkaline electrolytes. They are also the catalysts of choice for industrial alkaline water electrolysis. Despite decades of research, the atomic-scale structures of these materials, particularly key Ni (oxy)hydroxide hosts, remain elusive. This presentation aims to fill this critical knowledge gap by combining rigorous Density Functional Theory calculations with in situ Wide Angle X-ray Scattering techniques under quasi-steady state electrochemical cycling conditions. This unique combination has enabled us to unveil the in-situ structures and (ir)reversible transformations of pure undoped Ni (oxy)hydroxides. Such an advance consequently allows us to transcend the limitations of previous modeling based on approximated structures. Specifically, based on the newly identified actual in-situ structures, we discover the existence of a previously unknown synergy at the reaction centers, coupled with the polaron effects, in promoting the oxygen evolution reaction. Such a finding sheds light on the catalytic active sites and oxygen evolution reaction pathways, particularly the exceptional activity of multiple Fe reaction centers on Ni oxyhydroxides. In addition, we found that such a phenomenon is general and also exists on NiM and CoM layered double hydroxides,1, 2 A2B2O7 pyrochlores,3 layered Co oxyhydroxides intercalated with phenanthroline through non-covalent ligand-oxide interaction.4

References:

Dionigi, F.; Zeng, Z.; Sinev, I., et al. Nature Communications
2020, 11, (1), 2522.

Dionigi, F.; Zhu, J.; Zeng, Z.; Merzdorf, T.; Sarodnik, H.; Gliech, M.; Pan, L.; Li, W.-X.; Greeley, J.; Strasser, P. Angew. Chem., Int. Ed.
2021, 60, (26), 14446-14457.

Yan, J.; Zhu, J.; Chen, D.; Liu, S.; Zhang, X.; Yu, S.; Zeng, Z.; Jiang, L.; Du, F. Journal of Materials Chemistry A
2022, 10, (17), 9419-9426.

Wu, Q.; Liang, J.; Xiao, M.; Long, C.; Li, L.; Zeng, Z.; Mavrič, A.; Zheng, X.; Zhu, J.; Liang, H.-W.; Liu, H.; Valant, M.; Wang, W.; Lv, Z.; Li, J.; Cui, C. Nature Communications
2023, 14, (1), 997.
Electrocatalysis of Oxygen Evolution by Metal Oxides through Atomically-Thin Carbon
Authors: Newton Graham , Townsend William , Johnson Lee R , Khlobystov Andrei , Walsh Darren Anthony
Published: December 2024

The oxygen evolution reaction (OER) is slow at most electrocatalysts and the preparation of inexpensive, sustainable, stable, and high-performance OER electrocatalysts remains the largest obstacle in the development of new electrolyzers. Carbon-coated metal/metal oxide (nano)particles have been used in such applications but the role played by the carbon coatings has provoked debate in the field and is poorly understood. Here, we show that the coating itself acts as the active site in OER, with the underlying material activating the carbon through a charge-transfer mechanism. We demonstrate this phenomenon by encapsulating < 2 nm metal-oxide (MOx) electrocatalyst nanoparticles within single-walled carbon nanotubes (SWNT) to form Co3O4@SWNT, RuO2@SWNT and IrO2@SWNT. Access of electrolyte to the encapsulated metal oxides is blocked by plugging the SWNTs with fullerenes, which shuts off redox processes inherent to the encapsulated metal oxide but does not affect catalytic activity, showing that the carbon surface is the active OER site. This conclusion is supported by Tafel analysis which demonstrates that the rate-determining step for the OER is the same at MOx@SWNT and pristine SWNTs but different to that at bare MOx. In-situ electrochemical Raman spectroscopy and computational analysis demonstrate that charge transfer from the carbon shell to the metal oxide occurs during the OER. This charge transfer results in a decrease in electron density on the carbon surface, which may facilitate binding of –OH to the carbon surface. This is the first step in the OER and may be key to the activity of the hybrid nanomaterials. This understanding of how carbon coatings play an active role in electrocatalytic reactions is crucial for the development of future electrocatalysts for the OER, and the proposed charge transfer-driven mechanism could be tuneable to both oxidative and reductive reactions. These insights indicate that the route to high performance, sustainable electrocatalysts may be through electronic modification of conductive carbons, potentially through an interaction with inexpensive redox-active material which could be directed towards the development of reduction or oxidation electrocatalysts.
Atomically Dispersed Ru on Ni Catalyst-Integrated Porous Transport Electrode for Proton Exchange Membrane Water Electrolyzer
Authors: Yeo Kyeong-Rim , Kim Soo Kil
Published: December 2024

Water electrolysis is an eco-friendly technology that does not emit pollutants when connected to renewable energy and can obtain high purity hydrogen (>99.9%) through the process of electrochemically splitting water molecules into hydrogen and oxygen. Among them, proton exchange membrane water electrolysis (PEMWE) has the advantage of high current density, low gas crossover, high gas purity, and high pressure operation compared to existing alkaline water electrolysis.[1] The material that shows the best catalytic activity in the hydrogen evolution reaction (HER) is platinum (Pt), which has a low overpotential and high exchange current density. Therefore, it has been the subject of various studies in the fields of catalysis and electrochemistry to investigate the effect of the size and structure of Pt nanoparticles and nanostructures on electrocatalytic activity.[2,3] However, due to the limited resources and high cost of platinum, the use of platinum acts as an obstacle to commercialization of PEMWE. Accordingly, many studies have been conducted on the development of low-platinum hydrogen generation catalysts to reduce platinum usage and increase activity. has been in progress.

In this study, a porous transport electrode incorporating a Ni catalyst in which Ru was atomically dispersed was fabricated through simple electrodeposition. The Ni98.1Ru1.9 catalyst doped with trace amounts of Ru showed a low overpotential of 35 mV at –10 mA cm-2 for hydrogen evolution and a low Tafel slope of 31 mV with excellent stability. It was found that optimized hydrogen adsorption strength and improved mobility of hydrogen adsorbates on the catalyst surface contributed to high performance through density functional theory calculations. As a result of further verifying the performance and durability by applying Ni98.1Ru1.9 to the hydrogen electrode of the PEMWE cell, it showed excellent performance of 6.0 A cm-2 at 2.25Vcell and high stability operating at 1 A cm-2 for 50 hours.[4]

[References]

[1] M. F. Kaya, N. Demir., Fuel Cells, 17 (2017) 37–47

[2] J. Solla-Gullón, R. Gómez, A. Aldaz, J.M. Pérezet., Electrochemistry Communications, 10 (2008) 319–322

[3] Maryam Bayati, Jose M. Abad, Craig A. Bridges, Matthew J. Rosseinsky, David J. Schiffrin, Journal of Electroanalytical Chemistry, 623 (2008) 19–28

[4] K-R. Yeo, H. Kim, K-S Lee, S. Kim, J. Lee, H. Park, S-K Kim, Applied Catalysis B: Environment and Energy, 346 (2024), 123738
Tracking the Evolving Structure of Nickel–Iron Oxyhydroxide Oxygen Evolution Electrocatalysts in Alkaline Media
Authors: Cullen David A. , Yu Haoran , Hermann Raphael P. , Lyu Xiang , Serov Alexey , Osmieri Luigi , Zelenay Piotr , Park Jaehyung , Kropf A. Jeremy , Sweers Matthew , Myers Deborah J. , Kreider Melissa E , Alia Shaun M , Mizrahi Michael , Elbaz Lior
Published: December 2024

Anion exchange membrane water electrolyzers (AEMWEs) present a lower cost option for hydrogen generation with respect to their proton exchange membrane counterpart due to the possibility of utilizing platinum group metal-free catalysts to drive the oxygen evolution reaction (OER) at the anode. The addition of iron (Fe) to nickel-(oxy)hydroxides has been shown to significantly enhance the OER catalytic activity, although the precise mechanisms are still under debate. A clearer picture of the structure of these catalysts, particularly during operation, is needed in order to further improve their performance and durability.

In this work, a range of in situ and ex situ characterization techniques are used to study NiFe-based OER catalysts synthesized via different approaches [1]. High resolution electron microscopy will be presented showing how the as-synthesized structure of these materials transforms dramatically following break-in and initial performance evaluation [2]. The results of complementary in situ Mössbauer and X-ray absorption spectroscopy experiments which track the changing oxidation states of Fe and Ni under applied potential in aqueous media will also be presented. The structural changes related to catalyst degradation following extended operation in membrane electrode assemblies will also be discussed.

References

[1] W. Moschkowitsch et al., Nanoscale, 14 (2022) 18033-18040

[2] L. Osmieri et al., Applied Catalysis B: Environment and Energy 348 (2024) 123843
Metal-Organic Framework-Derived PGM-Free Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Media
Authors: Zhang Hanguang , Zelenay Piotr
Published: December 2024

Nickel (Ni)-based materials are among the most promising platinum group metal-free (PGM-free) electrocatalysts for hydrogen evolution reaction (HER) in alkaline media. With the growing demand for green hydrogen production, the HER activity of Ni-based catalysts must be enhanced to meet the goal of low-cost and sustainable hydrogen production.1 Carbon-supported Ni-based catalysts are typically prepared through the heat-treatment of Ni-based precursors with carbon supports.2 However, the catalysts obtained by this approach suffer from high content of inactive carbon and a non-uniform distribution of Ni-based nanoparticles, leading to low HER activity. These issues amplify the need for novel Ni-based catalysts with a well-controlled catalyst structure designed for maximizing catalyst utilization and minimizing electrode thickness.

In this talk, we will present our recent progress in developing Ni-based HER catalysts derived from metal-organic framework (MOF) precursors. Taking advantage of the characteristics of well-defined structure, high porosity, and flexible chemistry of MOF precursors3, the MOF-derived catalysts exhibit very promising activity towards HER allowing to reach 10 mA/cm2 at an overpotential of less than 100 mV in alkaline media. We will discuss how the ligand in MOF precursors and heat treatment conditions influence the structure and HER performance of Ni-based catalysts. This understanding promises to provide much needed guidance for the advancement of Ni-based catalysts for HER in alkaline media.

Acknowledgement

This work has been partially supported by the Center for Alkaline Based Energy Solutions (CABES) funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE-SC0019445.

References:

DOE Energy Earthshots Initiative: Hydrogen Shot. U.S. Department of Energy, 2021. https://www.energy.gov/eere/fuelcells/hydrogen-shot.

Jang, M. J.; Yang, J.; Jeong, J.; Kim, G. H.; Kwon, C. Y.; Myung, N. V.; Lee, K. H.; Choi, S. M. ACS Sustain. Chem. Eng.
2021, 9, 12508.

Zhou, H.-C.; Long, J. R.; Yaghi, O. M. Chem. Rev.
2012, 112, 673.
Operando XPS Study of Tungsten Oxide-Supported Iridium Nanoparticles: High-Efficiency Water Splitting Catalysts in Acidic Environments and PEM Electrolysis
Authors: Chueh Lu Yu , Hsu Yu Wei , Wu Chang-Ming , Tsai Meng-Hsuan , Yang Chueh-Cheng , Wang Chia-Hsin , Pan Yung-Tin
Published: December 2024

In the quest for sustainable energy solutions, our recent submission targets a critical challenge in the realm of hydrogen energy production, specifically within Proton Exchange Membrane Water Electrolysis (PEMWE) systems. The overarching goal is to reduce the reliance on iridium (Ir), a scarce and expensive material, thereby enhancing the economic feasibility and sustainability of hydrogen production.

To achieve this, we have refined our synthesis approach, focusing on the dispersion of Ir within tungsten oxide supported Ir nanoparticles (NPs). A comparative analysis of different solvents (organic versus aqueous) and concentrations revealed that aqueous solutions at lower concentrations offer superior catalyst dispersion and a higher loading of iridium. This outcome is pivotal for creating a continuous conductive layer essential for PEMWE applications, where the efficiency of water electrolysis can be significantly impacted by the catalyst's performance.

Our innovations have led to a substantial increase in activity under acidic conditions, as evidenced by Rotating Disk Electrode (RDE) testing. Here, we achieved a performance enhancement of 3.2 times at 1.55V compared to Iridium Black, and remarkably, over 30 times when juxtaposed with crystalline Iridium Oxide. Such advancements underscore the potential for considerable efficiency improvements in hydrogen production.

Our prior investigations, through Synchrotron-based X-ray Photoelectron Spectroscopy (XPS) has provided insights into the electron donation capabilities of Tungsten Oxide during the Oxygen Evolution Reaction (OER) process. This electron donation boosts the electron density on iridium, thereby amplifying its catalytic activity and mitigating over-oxidation risks.

Our investigation also extended to operando-Synchrotron-based XPS analyses of in-situ acidic electrolysis reactions under catalyst-coated membranes. Notably, at low iridium loadings, we observed that Iridium Black is prone to over-oxidation and activity loss at voltages exceeding 1.7 V (vs. RHE), a challenge not faced by tungsten oxide supported Ir, which demonstrated stable performance signals and avoided current density degradation at higher voltages.

By successfully implementing this advanced material in PEMWE applications, we have made significant strides towards achieving high efficiency with low Ir loading. This breakthrough not only enhances the economic viability of hydrogen energy production but also contributes to the broader adoption of green energy solutions, marking a significant advancement in the pursuit of sustainable and efficient membrane electrode assemblies for hydrogen production.
Spatial Atomic Layer Deposition to Manufacture Catalyst Coated Electrodes for PEM Water Electrolysis with Ultra-Low Loadings of Iridium
Authors: Diaz-Morales Oscar , Shen Jie , Sidney Santana Cássia , Bens Frennie , Dijk Bas
Published: December 2024

Proton Exchange Membrane Water Electrolysis (PEMWE) has great potential to produce hydrogen with renewable energy sources (green hydrogen production) because the technology can operate at high-power density with rapid startup times. However, PEMWE relies on scarce materials. Iridium usage as catalyst in PEMWE is a major point of attention because this metal is the second scarcest in our planet. State-of-art PEM electrolysers use approximately 2.5 g of iridium per kilowatt of power, this would translate in requiring >100% of the yearly global iridium production to sustain green hydrogen production at the multi-gigawatt power level [1]. Therefore, it is key to reduce the usage of iridium in PEMWE and to manufacture components to ease up recyclability upon reaching end of life.

In this work, we show our advances in manufacturing anodes for PEMWE with (ultra-)low loadings of iridium. The anodes were made by depositing iridium thin films on porous transport layers (catalyst coated electrode, CCE) by Spatial Atomic Layer Deposition (sALD) [2]. This manufacturing approach allows atomic level control over the amount of material deposited and it ensures high uniformity and conformality of the deposited films. By manufacturing CCEs with sALD, we reduced the amount of iridium used in the PEM electrolysis more than 100 times compared to the state of the art. Importantly, we found that the structure of the porous substrate, the manufacturing process and the usage of protection coatings are crucial to get good performance and enhance the durability of CCEs in PEMWE (see Figure 1).

Our work showcases the potential of using sALD to produce high performing and durable PEMWE electrodes. This manufacturing approach can minimize the usage of iridium in PEM electrolysers and has the high throughput needed to fulfill the demand for components that will come along with the multi-gigawatt electrolysers deployment envisioned in the near future. Furthermore, the usage of CCE in PEMWE separates the inorganic components of the electrolyser (i.e. catalyst layer and porous transport layer) from the organic part (i.e. proton exchange membrane), which will make it easier to recycle PEMWE components.

References

[1] Gavrilova, A., Wieclawska, S.M. “Towards a green future. Part 2” (2021). TNO report 21-12158.

[2] Shirvanian, A. P. Thin film porous catalyst sheet, WO 2023287284 A1, 19 January 2023.

Figure 1
Doped Rutile TiO2 Nanowires As Supports for Durable Proton Exchange Membrane Water Electrolyzers
Authors: Murphy Eamonn , Li Kui , Diaz-Abad Sergio , Komini Babu Siddharth , Wang Xiaojing , Spendelow Jacob S.
Published: December 2024

Proton exchange membrane water electrolyzers (PEMWEs) are a promising technology to achieve green hydrogen. Currently, PEMWE cost is dominated by the high loadings of ultra-scarce Ir-based catalysts, which remains the only metal that demonstrates a promising balance of activity and durability for the oxygen evolution reaction (OER), the limiting reaction of PEMWEs.1 Aimed at improving the activity and durability, current PEMWEs use high Ir loadings up to several mgIr cm-2. The high Ir loadings provide a pathway for electronic transport through particle-particle contacts, while yielding a thicker catalyst layer to maintain electronic conductivity as the nanoparticles degrade through operation. The DOE Hydrogen Earthshot aims to reduce the cost of green hydrogen by 80%. To realize this ambitious goal, Ir loadings must be significantly reduced, while maintaining conductivity and durability, which remains a major challenge.

In this study, we demonstrate the effectiveness of stable, conductive, Nb-doped rutile TiO2 (Nb-TiO2) nanowires as supports, for durable PEMWEs at low Ir loadings. The Nb-TiO2 nanowires provide an enhanced electron transport pathway through a 1-D morphology, reducing particle-particle contact resistances. Through a photodeposition-based approach2, a continuous layer of IrOx nanoparticles is formed on the surface of the Nb-TiO2 nanowire. The activity of the IrOx/Nb-TiO2 nanowire is evaluated in both a rotating disk electrode and PEMWE configuration, outperforming an unsupported commercial IrOx catalyst. Accelerated stress tests cycling between 2.0 V and 1.45 V holds over 300 hours, show the superior durability of the IrOx/Nb-TiO2 nanowire catalyst at a low Ir loading of 0.12 mgIr cm-2
, compared to the commercial IrOx catalyst. Our results demonstrate a promising platform to achieve highly active and durable Ir-based catalysts in practical PEMWEs at low Ir loadings.

Acknowledgement

This research is supported by the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (20240061DR) and US Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office (HFTO).

References:

[1] Thao, Nguyen Thi Thu, et al. Small Science 4.1 (2024): 2300109.

[2] Hoffmeister, Darius, et al. ChemRxiv. (2024)
Advanced Nano-Porous Thin Films: Automating Water Electrolysis with Spark Ablation Printing
Authors: Irtem Erdem , Arici Ece , Asperti Simone , Schouten Niels , Van Vugt Aaike
Published: December 2024

The current commercial loading of Platinum grade materials (PGMs) per membrane electrode assembly (MEA) stands at 2 mg/cm2, necessitating significant efforts to redesign electrocatalyst materials through a nano-architecture approach, requiring a thousandfold increase in surface area (from µm to nm scale) and a tenfold reduction in mass loading (from mg to µg). This objective can be realized through innovative surface engineering and manufacturing techniques as traditional wet synthesis methods pose several steps leading to spot errors (during ink formulation and coating) and high manufacturing costs (during drying steps) hampering scale-up efforts especially for low PGM loading < 0.5 mg/cm2 in PEM-WE.

VSPARTICLE developed a nano-printing technology utilizing spark ablation. This dry-synthesis method generates nanoparticle films only by using metal rods and electricity, and immobilize nano-porous electrocatalyst thin films on any substrate. In this presentation, we will unveil the latest findings concerning oxygen evolution reaction (OER) electrodes employing Ir-based and Ni-based catalysts produced through the innovative VSP-P1 nano-printing technology. The MEAs prepared using spark ablation had significantly lower loading (e.g., 0.1 and 0.4 mg/cm2) than the commercial state-of-the-art without compromising performance. The study integrates comprehensive flow-cell experiments, meticulous control tests, and characterization techniques on proxy samples, leveraging the versatility of VSP-P1 to create identical nano-porous films on various substrates. The scalability of this dry manufacturing process, coupled with rapid iteration capability for tuning material parameters and test-beds, promises a tenfold acceleration in electrocatalyst utilization.

In conclusion, this presentation unveils an efficient strategy for catalyst utilization through nano-printed layers, significantly reducing the time required to bring novel materials to market. The methodology outlined herein holds great promise for advancing hydrogen deployment and sustainable transitions in hard-to-decarbonize sectors.

Figure 1. a) The automated print technology in process based on NanoPrinter (P1), b) printing of Ir process, c) cross sectional and HR-SEM image of the thin film, d) PEMWE results Ir(VSP)-NPs tested at ambient temperature and pressure

Figure 1
Solid State Synthesis and Catalytically Active Nanoparticle Exsolution As a Novel Approach for HER Electrode Fabrication
Authors: Reinke Jakob Michael , Li Ruihan , Yi Zhiying , Seitz Linsey C , Barnett Scott A
Published: December 2024

Increased demand for green hydrogen as part of a global effort to decarbonize will place a significant strain on global precious metal resources and drive up the price of electrolyzers. This study explores a new way of producing oxide electrode materials for proton exchange membrane electrolyzer cells (PEMECs) that may help decrease material and processing costs while potentially improving catalyst lifetime. The method is the so-called “exsolution” technique, previously used in high temperature catalysts and fuel cell electrodes (1). In exsolution, a high-temperature reduction process causes one or more cations in an oxide to be reduced to form surface metal nanoparticles. For example, Sr0.95Ti0.3Fe0.63Ru0.07O3-δ (STFR) has been shown to be an effective solid oxide cell fuel electrode where exsolution forms Ru-Fe nanoparticles that substantially enhance electrode performance (2).

Here, we compare the ambient temperature catalytic activity for the acidic hydrogen evolution reaction (HER) of pristine STFR and STFR exsolved for varying durations at temperatures ranging from 500 to 800℃ in a gas mixture of 97% H2/3% H2O. The exsolved materials demonstrate superior HER activity and stability compared to pristine STFR. As shown in Figure 1, the initial overpotential required to achieve a current density of -10mA/cm2
geo was decreased from 388 mV without exsolution to 141 mV after 4h exsolution at 700 ℃. Overpotentials generally decrease further after 1000 LSV cycles.

This paper will also show the effect of varying reduction times and gas compositions on the resulting electrocatalytic activity. Results for a different electrode composition, Sr0.95Ti0.3Fe0.63Ni0.07O3-δ (STFN), will also be presented. The electrochemical results will be related to the size and density of exsolved nanoparticles.

Figure 1: Linear Sweep Voltammetry polarization curves measured at 5 mV/s in 0.5M H2SO4 at room temperature for as-prepared STFR electrodes compared with STFR electrodes that had been reduced at various temperatures for 4 hours in 97% H2, 3% H2O prior to testing. Solid lines show the first sweep and dashed lines show the polarization after 300 voltammetry cycles for STFR without exsolution, and 1000 CVs for the exsolved STFR electrodes.

D. Neagu, J. T. S. Irvine, J. Wang, B. Yildiz, A. K. Opitz, J. Fleig, Y. Wang, J. Liu, L. Shen, F. Ciucci, B. A. Rosen, Y. Xiao, K. Xie, G. Yang, Z. Shao, Y. Zhang, J. M. Reinke, T. A. Schmauss, S. Barnett, R. Maring, V. Kyriakou, U. Mushtaq, M. N. Tsampas, Y. Kim, R. O'Hayre, A. J. Carrillo, T. Ruh, L. Lindenthal, F. Schrenk, C. Rameshan, E. I. Papaioannou, K. Kousi, I. Metcalfe, X. Xu and G. Liu, Journal of Physics: Energy (2023).

R. Glaser, T. Zhu, H. Troiani, A. Caneiro, L. Mogni and S. Barnett, Journal of Materials Chemistry A, 6, 5193 (2018).

Figure 1