bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoparticels Exsolution on Perovskite Oxides: From Growth Mechanism to Energy Conversion Applications
Authors: Kim Yo Han , Jeong Hyeongwon , Won Bo-Ram , Park Dayoung , Myung Jae-Ha
Published: December 2024

Exsolution method is a bottom-up process for growing uniformly distributed nanoparticles embedded on the oxide surface, exhibiting excellent activity and stability in energy conversions. Despite suggestions of diverse techniques for controlling and optimizing nanoparticle exsolution, research for quantitative control remains insufficient. Herein, we investigate the distribution of endogenous nanoparticles in the bulk of the fully reduced oxide, providing evidence of ion diffusion limitation rather than surface reduction limitation. Thus, we suggest a diffusion limitation model to understand the growth behavior of exsolved nanoparticles on the oxide support. Based on the experimental results, a theoretical model is developed using Fick’s laws and confirmed in designed perovskite oxides in which their Ni doping levels are controlled within the range of solubility. Their exsolution tendencies in the gas reduction, depending on doping level, reduction temperature, and time, are matched with the theoretical model. According to experimental and theoretical results, highly Ni-doped perovskite oxides are employed to improve exsolution and achieve high performance in energy conversions, including solid oxide cells and reforming. This framework between experimental and theoretical approaches provides insight for understanding and controlling nanoparticle exsolution on perovskite oxides.
Development of Superior-Performance, High-Durability and Low-Cost Reversible Solid Oxide Cell for Power Generation and Hydrogen Production
Authors: Minh Nguyen Q. , Lee Sanghoon , Ryu Sangbong , Thieu Cam Anh , Tran Quang Tuyen , Lin Haichen , Liu Ping
Published: December 2024

A superior-performance, high-durability and low-cost reversible solid oxide cell (RSOC) technology is under development for power generation and hydrogen production applications. This RSOC incorporates components made by sputtering which significantly enhance cell performance. Sputtering can be a cost-effective manufacturing process for making RSOC cells/components, especially thin-film components. This process eliminates the multiple cell thermal processing steps (with high heat treatment temperatures and lengthy firing times) commonly used in conventional processes, thus reducing cell fabrication cycle time and fabrication cost. This cell technology also includes non-strontium perovskite oxygen electrodes and/or nickel-substituted perovskite hydrogen electrodes. Non-strontium perovskite oxygen electrodes contains no strontium, thus unwanted strontium segregation and interactions with volatile chromium species to form strontium chromium oxides are avoided, resulting in increased electrode resistance to chromium poisoning. Nickel-substituted perovskite hydrogen electrodes, when exposed to reducing environment, will exsolve nickel to form fine particles imbedded in the oxide skeleton. For this embedded structure, volume changes upon reduction/oxidation (redox) are not significant. The hydrogen electrode based on this material is thus redox resistant. Nickel particles formed in this way have been shown to significantly reduce electrode polarization resistance, thus enhanced performance and exhibit high stability, thus increased durability. The paper discusses recent progress in the development and scaleup of the sputtering process and studies of oxygen electrodes based on lanthanum nickel cobalt perovskite (LNC) and hydrogen electrodes based on nickel-substituted lanthanum strontium cobalt iron perovskite (LSCFN).
Accelerating Development of Submicron-Thick Initiated Chemical Vapor Deposition (iCVD)-Derived Polymer Electrolytes for All Solid-State Batteries Via Pre-Screening Bulk Surrogates
Authors: Ford Hunter O. , Nuwayhid Ramsay , Chaloux Brian , Swift Michael W , Jayakody Nishani , Klug Christopher , Kim Youngchan , Liu Xiao , Jugdersuren Battogtokh , Long Jeffrey W. , Rolison Debra R. , Sassin Megan B.
Published: December 2024

Initiated chemical vapor deposition (iCVD) is an emerging method for generating submicron-thick, conformal polymer coatings on structurally complex substrates, including those of interest to all solid-state 3D batteries, fuel cells, and capacitive deionization devices. From the perspective of the energy-storage community, the utility of iCVD arises from the ability to create conformal polymer anion- or cation-conducting solid-state electrolytes, artificial solid-electrolyte interphase (SEI) layers, and surface property-modifying coatings. Expanding the library of polymer chemistries and structures beyond those obtained using standard vinyl-containing iCVD monomers is essential to address the challenges facing next-generation, advanced energy storage (e.g., cycle life, suppression of unwanted ion transport). However, opening up this synthetic property-performance space for iCVD-generated materials challenges the throughput of iCVD and greatly increases the number of characterization experiments. To circumvent this challenge, we previously reported that bulk poly(dimethylaminomethylstyrene), pDMAMS, synthesized using bulk solution polymerization serves as a surrogate for iCVD-derived pDMAMS.1,2 We now extend the viability of bulk polymer surrogates to other polymer chemistries as a pre-screening option to accelerate the design and evaluation of iCVD-derived solid-state polymer electrolytes. For a selected test case involving single-anion conducting alkaline polymer electrolytes, we demonstrate how trends observed in polymer design regarding ion/mass transport and morphology on traditional bulk-synthesized polymers translate to iCVD-prepared analogs of the same systems. For example, we show that for a co-polymer system comprising divinylbenzene (DVB) and quaternized dimethylaminomethylstyrene (p[DVB-DMAMS+], increasing the crosslinking DVB content decreases ionic conductivity and restricts dynamic freedom. Using this understanding, we formulate an appropriate pre-optimized iCVD-derived p[DVB-DMAMS+] electrolyte and verify that its performance trend aligns with that of the bulk copolymer.

1. Ford, Hunter O., et al. Non-line-of-sight synthesis and characterization of a conformal submicron-thick cationic polymer deposited on 2D and 3D substrates. RSC Applied Interfaces (2024); doi: 1039/d3lf00256j.

2. Ford, Hunter O., et al. Submicron-thick single anion-conducting polymer electrolytes. RSC Applied Interfaces (2024); doi: 10.1039/d3lf00257h.
Atomically Dispersed Metal Catalysts Promoting Selective Chlorine Evolution Reaction
Authors: Joo Sang Hoon
Published: December 2024

Chlorine evolution reaction (CER) is a key anodic reaction in the chlor–alkali electrolysis.1 Dimensionally stable anode (DSA), invented in the late-1960’s, has been predominantly used as a CER electrocatalyst in the chlor–alkali electrolysis.2 However, DSAs typically require at least 30 at% of Pt-group metal (PGM) to ensure electrical conductivity, raising up cost issue. In addition, they suffer from parasitic oxygen evolution reaction (OER), as the CER and OER share common active sites on metal oxide surfaces. Hence, the design of new CER electrocatalysts has been directed toward enhancing CER selectivity while saving the amount of PGM.3,4

In 2020, we developed a new CER electrocatalyst composed of single atomic Pt sites dispersed on carbon nanotubes (Pt1/CNT).5 The Pt1/CNT catalyst with Pt–N
x
active sites showed higher CER activity and selectivity than the commercial DSA and Pt NPs on CNT. Importantly, Pt1/CNT preserved ~100% selectivity even in low Cl− concentration, neutral pH, and seawater conditions, where the OER is thermodynamically more favored. Furthermore, Pt1/CNT exhibited unusual potential-dependent CER kinetics and mechanism, which are clearly distinguished from those of DSA.6 We also found the multiplicity of Pt–N
x
active sites, among which a genuine active site was identified.7

R. K. B. Karlsson, A. Cornell, Chem. Rev.
116, 2982 (2016).

S. Trasatti, Electrochim. Acta
45, 2377 (2000).

K. S. Exner, T. Lim, S. H. Joo, Curr. Opin. Electrochem.
34, 100979 (2022).

T. Lim, J. Kim, S. H. Joo, J. Electrochem. Sci. Technol.
14, 105 (2023)

T. Lim, G. Y. Jung, J. H. Kim, S. O. Park, J. Park, Y.-T. Kim, S. J. Kang, H. Y. Jeong, S. K. Kwak, S. H. Joo, Nat. Commun.
11, 412 (2020).

T. Lim, J. H. Kim, J. Kim, D. S. Baek, T. J. Shin, H. Y. Jeong, K.-S. Lee, K. S. Exner, S. H. Joo, ACS Catal. 11, 12232 (2021).

J. Cho, T. Lim, H. Kim, L. Meng, J. Kim, S. Lee, J. H. Lee, G. Y. Jung, K.-S. Lee, F. Viñes, F. Illas, K. S. Exner, S. H. Joo, C. H. Choi, Nat. Commun.
14, 3233 (2023).
Oxide Encapsulated Ruthenium Oxide Catalysts for Selective Oxygen Evolution in Unbuffered pH Neutral Seawater
Authors: Bushiri Daniela Asifiwe , Baxter Amanda , Odunjo Onaolapo , Fraga Alvarez Daniela V. , Yuan Yong , Chen Jingguang G , Esposito Daniel V.
Published: December 2024

Direct seawater electrolysis is a promising approach to producing green hydrogen in water-scarce environments using renewable energy. However, the undesirable chlorine evolution reaction (CER) and hypochlorite evolution reaction (HCER) compete with the desired oxygen evolution reaction (OER) at the anode electrocatalyst. This issue is most pronounced in unbuffered pH neutral solutions due to local acidification resulting from the OER. To overcome this challenge, this study provides a comprehensive evaluation of the use of silicon oxide (SiOx) and titanium oxide (TiOx) nanoscale overlayers coated on metallic ruthenium (Ru) and ruthenium oxide (RuOx) thin film electrodes and their ability to block chloride ions from reaching active sites during operation in unbuffered 0.6 M NaCl electrolyte. Using a combination of (electro)analytical techniques, encapsulated RuOx anodes are shown to effectively suppress Cl- transport to buried catalyst active sites while allowing for the desired OER to occur, leading to increases in OER faradaic efficiency at moderate overpotentials. Evidence for the ability of SiOx overlayers to block Cl- ions from reaching the active buried interface was obtained by monitoring the OH stretching mode of OH adsorbates using in situ Raman spectroscopy. This study also reports trade-offs between the activity, selectivity, and stability of bare and encapsulated Ru and RuOx electrocatalysts, finding that the magnitude of these trade-offs strongly depends on the complex interplay between electrode architecture, material properties, and catalytic performance, especially in unbuffered pH neutral seawater.
Intermetallic Single-Atom Alloy Bimetallene for Electrosynthesis of Ammonia from Nitrate
Authors: Tang Sishuang , Xie Minghao , Li Zhao , Yu Guihua
Published: December 2024

Ammonia (NH3), as a high-value industrial chemical and hydrogen carrier, can be synthesized via more sustainable electrocatalytic nitrate reduction reaction (NO3RR). The performance of an electrocatalyst is related to a number of factors, one of which is the intrinsic activity of metals (metal d-band center) that affects the adsorption energy of reaction intermediates. Intermetallic single atom alloys (ISAAs) is an emerging class of alloys where contiguous metal atoms are isolated into single sites by another metal. Such arrangement not only optimizes the density of single atoms which already maximizes atom utilization efficiency, but also modulates the hybrid orbitals of the intermetallics. Herein, we report ISAA In-Pd bimetallene that consists of Pd single atoms being surrounded by In atoms. The ISAA bimetallene can achieve an NH3 Faradaic efficiency of 87.2%, a yield rate of 28.06 mg h-1 mgPd
-1, and an outstanding stability with increased activity and selectivity over 100 h and 20 cycles. DFT calculations reveal that, owing to the close proximity of Pd single atoms and their surrounding In atoms, the p-d hybridization of In-p and Pd-d states around the Fermi level were greatly narrowed, resulting in a more favorable adsorption and lower energy barrier for NO3RR. The ISAA bimetallene can further be used as a cathode in a Zn-NO3
- flow battery setup, achieving a power density of 12.64 mW cm-2 and a FE of 93.4% for NH3 synthesis.

Acknowledgements: This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award DESC0019019, the Welch Foundation Award F-1861, and the Camille Dreyfus Teacher−Scholar Award. XAS measurements were done at 20-BM at the Advanced Photon Source of the Argonne National Laboratory. The use of APS of ANL is supported by the DOE under Contract No. DE-AC02-06CH11357.
Low-Temperature Seawater Electrolysis for the Removal of Organic Contaminants and Simultaneous Hydrogen (H2) Generation
Authors: Lopez-Ruiz Juan A. , Boruah Bhanupriya , Strange Lyndi E. , Royer Nathanael , Riedel Nickolas W , Talukdar Biva
Published: December 2024

Water (H2O) electrolysis represents a sustainable approach to produce green hydrogen (H2); however, the high energy cost (2H2O → 4H2+ O2, ∆H° = 286 kJ/mol H2, E° = −1.23 V) associated with water electrolysis and electricity cost (>$50/MWh) results in a minimum H2 selling price ≈$4/kg H2. Therefore, we need to find an alternative process to generate H2 to meet the current U.S. Department of Energy's (DOE's) Energy Earthshots of $1/kg H2 in one decade.

Seawater represents an earth abundant natural H2O source for H2 generation in island and coastal communities. However, there are several technical challenges hindering its widespread implementation such as the corrosive nature of seawater and the production of poisonous chlorine gas (Cl2) via the chlorine evolution reaction (CER: 4Cl- → Cl2 + 4e-, E° = 1.36 V vs. RHE). The CER competes against the oxygen evolution reaction (OER: 2H2O → 4H+ + 4e- + O2, E° = 1.23 V vs. RHE), thus inhibiting the production of e- and H+ needed for the H2 production via the hydrogen evolution reaction (HER: 4H+ + 4e- → 2H2, E° = 0.0 V vs RHE). Instead, we propose to use the full electrocatalytic oxidation (FECO) of naturally-occurring and artificially-made organic molecules to generate H2 (e.g., CH3COOH + 2H2O → 2CO2 + 8e- + 8H+, E° = −0.02 V vs RHE) which occurs at >1 V lower potential than CER and OER. As opposed to traditional H2O electrolysis that requires clean water streams, the proposed electrolysis technology can use readily available H2O streams containing organic molecules (e.g., municipal wastewater) combined with seawater to generate H2 while removing the undesirable organic contaminants.

In this work, we compare the performance of heterogeneous electrocatalysts for the FECO of organic molecules present in wastewater in a model seawater electrolyte (0.1−0.6 M NaCl) at room temperature. PECO electrocatalysts were developed and tested using real wastewaters derived from several sources including the hydrothermal liquefaction (HTL) of food waste. We synthesized the PECO electrocatalysts using both platinum-group metals (PGM) as well as base-group metals (BGM) and tested them as a function of half-cell potential. Our results show that both PGM- and BGM-based bimetallics improve the activity and stability compared to the baseline RuO2-based catalysts.

Figure 1
Nitrogen-Rich Functionalized Carbon Wrapped on Cop/Ag: A Dynamic Multifunctional Electrocatalyst for Zinc-Air Battery Driven Water Splitting System
Authors: Surendran Subramani , Lee Dong-Kyu , Janani Gnanaprakasam , Yuvaraj Subramanian , Sim Uk
Published: December 2024

Hybridization of nanomaterials, encompassing two or three active elements, is a prominent phenomenon that enthralls synergistic properties to strongly inspire the prompt development of energy conversion and storage systems. Here, we account for a novel hybrid CoP/Ag@NC nanocomposite as a multifunctional electrocatalyst for efficient water splitting and Zn-air battery systems. The hybridization of the CoP nanostructure was engineered by disseminating the Ag nanoparticles in CoP wrapped meticulously by polymerization. The prepared hybrid CoP/Ag@NC nanocomposite bestows a combination of two elements with distinct properties that synergistically influence the electrode kinetics by adequately enhancing the transfer of electrons that promote superior electroactivity. The hybrid CoP/Ag@NC nanocomposite as a multifunctional electrocatalyst reveals outstanding performance by imposing a positively shifted half-wave potential during ORR and minimal overpotentials during OER and HER, respectively. Furthermore, the designed laboratory-scale Zn-air battery-driven water splitting system was developed and practically demonstrated. This work anticipates the fabrication of cost-effective multifunctional electrocatalysts from the hybridization of nanomaterials to inspire the progression of cutting-edge energy conversion and storage systems.

Figure 1
Evaluating the Measurement Uncertainty of Single Cell PEMFC Performance
Authors: Goh Jonathan , Smith Graham
Published: December 2024

A single cell proton exchange membrane fuel cell (PEMFC) is commonly used as a screening test to assess the impact of materials and operating conditions on these devices, with its performance commonly stated in terms of cell voltage at a given current density. Although standardised testing protocols exist and have been widely adopted, a universal method of assessing the uncertainty on the results has yet to be established. This complicates the task of comparing results/measurements made in different labs and evaluating the reliability of the conclusions. In this work, we estimated the uncertainty on PEMFC performance running at static standard operating conditions. Using results across three identical repeats and a sensitivity analysis of the various controllable input parameters to the fuel cell, we arrived at an expanded measurement uncertainty (k=2) for cell voltage of 32 mV at 1 A cm-2. The largest contributors to the measurement uncertainty were clearly air flow rate (stoichiometry) and cathode pressure.

Figure 1
Theory Guided Discovery of Superior Ru-Based Electrocatalyst for Durable Acidic Oxygen Evolution Reaction
Authors: Zhou Li Qin , Wang Siwen , Ling Chen
Published: December 2024

Water electrolysis (WE) using hydrogen evolution reaction is widely recognized as a promising method for clean and sustainable hydrogen production. The currently dominant alkaline-based water electrolysis encounters several challenges including high ohmic resistance, limited current density, low efficiency, and poor long-term stability. Proton exchange membrane (PEM) electrolysis can tackle these challenges by providing efficient proton transfer. However, sluggish oxygen evolution reaction (OER) in acid has been a major long-existing obstacle in PEM systems and, therefore, has attracted great research interest.

Due to its high activity and durability, IrO2 is currently considered the only practical OER electrocatalyst in PEM devices. However, Ir’s high cost and low global reserve limit its large-scale applications. Hence, less-expensive catalysts for acidic OER are in great demand. RuO2 has been recognized as an attractive alternative to IrO2 because Ru is ~100x abundant and costs ~10x less. Although RuO2 presents higher activity than IrO2, it deteriorates severely in a few hours due to its dissolution under oxidizing conditions. Its long-term stability remains a big challenge.

To overcome the challenge of improving the stability of Ru-based oxides, in this work we provide a rigid theoretical framework of RuO2 dissolution under the influence of other metal species. We show that the stability of Ru-based oxides could be controlled by varying the properties of incorporated metal oxides as well as the synergy to form a complex oxide. Surveying the Materials Project database led to the rationalization of a series of metal elements that could positively improve the stability of RuO2. Guided by our theoretical approach, we conducted high-throughput screening and experimental evaluation of Ru-based oxides for acid OER.

Our study discovered a novel Ru-based oxide with superior performance in acid OER application. A new wet-impregnation method was developed to synthesize the desired phase. The as-obtained product were uniform nanoparticles with diameters less than 5 nm in a single rutile structure. The new catalyst showed significantly better performance than pristine RuO2. In the rotating-disk-electrode experiment, our catalyst delivered a current density of 10 mA·cm-2 at an overpotential of less than 170 mV in 0.1 M HClO4. The catalyst exhibited a low degradation rate smaller than 25 μVh-1 for over 200 hours of operation at 10 mA·cm-2. Our results show great promise of Ru-based oxides as Ir-free electrocatalysts for acidic OER in PEM water electrolysis.
Performance Recovery in Irreversibly Degraded Polymer Electrolyte Membrane Fuel Cell for Enhanced Water Management
Authors: Kim Ji Yeon , Mortazavi Mehdi , Jung Sung Yong
Published: December 2024

Polymer electrolyte membrane fuel cells (PEMFCs) offer numerous advantages, such as low operating temperatures, ease of start-up and shutdown, and high power density. Recent researches have focused on enhancing their performance for various industrial applications, particularly in transportation fields including vehicles and drones. The gas diffusion layer (GDL) in PEMFC plays a key role in the transport of fuel, oxygen, and water. The physical and chemical degradation of GDL adversely affects the water management resulting in performance deterioration.

A major cause of GDL degradation in PEMFCs is the generation of hydrogen peroxide (H₂O₂) during the electrochemical reaction. H₂O₂ lead PTFE loss and carbon corrosion, and this degradation is irreversible. Although several studies demonstrate techniques for recovering performance for the reversible degradation, limited research exists on restoring performance in irreversibly degraded PEMFCs.

This study proposes a novel approach for the performance recovery in irreversibly degraded PEMFCs by superimposing acoustic pressure waves on the oxygen gas flow which enhances the water management ability [1]. To investigate the effect of proposed recovery technique, performances were compared with or without the superimposed acoustic pressure waves using a unit cell having 25 cm² active area. The 19 % decrease in performance with aged GDL was observed due to the reduction in the water management capability caused by the decrease of hydrophobicity.

The superimposed acoustic pressure waves led to a performance recovery of up to 9. This recovery is attributed to the enhanced removal of accumulated water on the GDL surface through external excitation, which facilitated oxygen supply and improved water discharge. The proposed the water management method can offer a promising solution for recovering performance in irreversibly degraded PEMFCs and has the potential to improve both performance and durability.

Acknowledgement

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. RS-2023-00208497, RS-2023-00219369).

Reference

[1] Kim, J. Y., Mortazavi, M., & Jung, S. Y. (2024). Improving polymer electrolyte membrane fuel cell performance and preventing flooding by exciting gas flow. Journal of Power Sources, 617, 235181.
Unveiling the Gas Evolution Dynamics in Electrochemical Processes via Acoustic Emission Analysis
Authors: Li Weihong , Fan Zhongyi , Zhang Lenan
Published: December 2024

Gas bubble evolution plays a pivotal role in water electrolysis. Electrochemical gas evolution reactions operating at high current densities represent a promising future trend for improving efficiency. However, the lack of reliable bubble detection methods in electrochemical gas evolution systems, as well as the limited understanding of bubble behavior at different current levels, hinder a comprehensive understanding of the actual bubble dynamics under various voltage and current conditions. To address this challenge, a novel methodology that utilizes acoustic emission signals is proposed to evaluate bubble behavior in the electrolyzer. The dynamic variations in the amplitude and frequency of the acoustic emissions can be correlated with the different stages of bubble evolution. By combining this acoustic technique with high-speed optical imaging, the relationship between the acoustic signal variations and the characteristics of bubble release under different voltage and current levels can be unvealed. Furthermore, clustering algorithms from machine learning are employed to determine bubble acoustic characteristics under various conditions based on the acoustic variations, which allows for redefining the polarization curve. These findings significantly enhance the understanding of the actual bubble behavior under different voltage and current intensities, going beyond the traditional pool boiling curve-based approach. The results demonstrate that acoustic emission can serve as an effective and non-intrusive tool for monitoring bubble formation in gas evolution reactions, making it particularly valuable for applications in non-transparent electrolyzer cells. This facile operating approach offers a new perspective for studying and optimizing electrochemical gas evolution processes.
Pore Uniformity Effect of Porous Transport Layers on Bubble Behaviors in PEM Water Electrolysis
Authors: Kim Seongkeun , Jung Sung Yong
Published: December 2024

Hydrogen, a clean energy source with high energy density and long-term storage potential, is gaining attention as a viable alternative to fossil fuels. Among various water electrolysis methods, Proton Exchange Membrane Water Electrolysis (PEMWE) is suitable for green hydrogen production due to its ability to operate efficiently at high current densities and low temperatures. A key component of PEMWE is the Porous Transport Layer (PTL), which facilitates oxygen gas discharge and water supply. However, to enable practical use of PEMWE at high current densities, effective oxygen removal without accumulation in the PTL is critical. While previous studies have explored the structural characteristics of PTL, research quantifying the effect of PTL pore uniformity on PEMWE performance remains limited. This study compared PTL samples with different pore uniformities using X-ray CT, investigated how these differences affect PEMWE performance, and analyzed bubble detachment characteristics on the PTL surface using high-speed imaging.

A specially designed cell with a transparent acrylic end plate was used to observe internal flow in the PEMWE system. The bubble detachment characteristics, including the number, frequency, and diameter of detached bubbles, were analyzed. The homogeneous PTL followed a normal distribution, while the inhomogeneous PTL exhibited a broader pore size range, deviating from this distribution. These structural differences led to significant performance variations. The homogeneous PTL had a bubble detachment rate of 9.49 bubbles/mm2, with an average detachment frequency of 30.5 Hz and a detachment diameter of 2.21 mm. In contrast, the inhomogeneous PTL exhibited a significantly lower detachment rate of 0.30 bubbles/mm2, a higher detachment frequency of 78.2 Hz, and a larger detachment diameter of 22.4 mm. Furthermore, when comparing the departure velocity, calculated by multiplying the detachment frequency by the bubble diameter, the homogeneous PTL achieved a velocity of 289.3 mm/s, approximately 3.2 times faster than the 89.6 mm/s observed in the inhomogeneous PTL. These findings suggest that a more uniform pore structure enables faster and more efficient gas removal, leading to enhanced PEMWE performance. Additionally, the high departure velocity in the homogeneous PTL indicates a more effective two-phase flow, which contributes to the improved water supply and gas discharge, thereby optimizing overall cell efficiency.

The homogeneous pore structures promote efficient gas discharge and water supply, leading to improved cell performance. These findings show the importance of designing PTLs with uniform internal pore structures to optimize PEMWE operation.

Acknowledgment

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00208497, RS-2023-00219369).
Impact of Composition, Pressure and Local Symmetry of Impurity Site on the Optical Properties of Phosphor Materials
Authors: Piasecki Michal , Brik Mikhail G. , Srivastava Alok M. , Khyzhun Oleg Y , Beers Wiliam W , Cohen William Erwin , Novita Mega , Stef Marius , Umar Zafari , Yamamoto Tomoyuki
Published: December 2024

The understanding of complex relationships between luminescent properties, local symmetry of an emitting center and type of chemical bonding on the host crystal structure provides a better insight into optical properties of materials. Moreover, tunability of the phosphors’ emission spectra by changing local environment around impurity center is attractive from the point of view of pressure sensors or lighting applications. We will discuss from the theoretical and experimental points of view some examples (semiconductors or insulators matrices with multivalent ions, either rare-earth (RE) or transition-metal (TM) chemical elements with unfilled 4f or 3d electron shells, as activators: respectively). The presentation also shows that the knowledge gained from the systematic study of the host-activator interaction can serve as a guide to practical improvement and tuning to desired values the key parameters of phosphors [1-9].

References:

[1] Alok M Srivastava, Mikhail G Brik, William W Beers, Chong-Geng Ma, Michal Piasecki, William E Cohen , J. Lumin. 257 (2023) 119709

[2] Andrei V Racu, Zoran Ristić, Aleksandar Ćirić, V Đorđević, G Bușe, Maria Poienar, Michael J Gutmann, Oleh Ivashko, M Ștef, Daniel Vizman, MD Dramićanin, Michal Piasecki, Mikhail G Brik, Opt. Mat.136, (2023) 113337

[3] M. G. Brik, W. W Beers, W. Cohen, S. A. Payne, N. J. Cherepy, M. Piasecki, A. M. Srivastava, Opt. Mat. 91 (2019) 338

[4] AM Srivastava, MG Brik, WW Beers, B Lou, C-G Ma, M Piasecki, W E Cohen, ECS J. Solid State Sci. Technol., 12 (2023) 066001

[5] Umar Zafari, Musashi Sagayama, Mekhrdod Subhoni, Alok M Srivastava, William W Beers, William E Cohen, Chong-Geng Ma, Michal Piasecki, Mikhail G Brik, Tomoyuki Yamamoto, Opt. Mat.: X, 16 (2022) 100197

[6] Zafari Umar, Mekhrdod S Kurboniyon, Oleg Khyzhun, Tomoyuki Yamamoto, Chong-Geng Ma, Mikhail G Brik, Michal Piasecki, J. Lumin. 266 (2024) 120278

[7] Mega Novita, Alok Singh Chauhan, Rizky Muliani Dwi Ujianti, Dian Marlina, Haryo Kusumo, Muchamad Taufiq Anwar, Michał Piasecki, Mikhail G Brik, J. Lumin. 269 (2024) 120476

[8] J Jedoń, Agata Lazarowska, Tadeusz Leśniewski, Sebastian Mahlik, MG Brik, M Piasecki, AM Srivastava, WW Beers, E Zych, Journal of Alloys and Compounds, 930 (2023) 167435

[9] Alok M. Srivastava, Mikhail G. Brik, Chong-Geng Ma, William W. Beers, William E. Cohen and Michal Piasecki, J. Phys. Chem. Lett. 15, XXX (2024) 4175–4184
Creation of a Two-Step Prediction Model of 4f-5d Transition Energies of Ce3+ in Garnet-Type Oxides Based on the Combination of First-Principles Calculations and Machine Learning
Authors: Mohd Razip Nora Izzati Binti , Novita Mega , Ogasawara Kazuyoshi
Published: December 2024

This study presents a novel approach which combines first-principles calculations with machine learning techniques to predict the 4f-5d transition energy of Ce3+ ions in garnet-type oxides. This is important in various technological applications, e.g., light-emitting materials, and solid-state lighting devices. However, it is difficult and time-consuming to accurately determine this energy using conventional methods. A linear regression model for the 4f-5d transition energy of Ce3+ in garnet-type oxides was created by machine learning, using electronic and structural parameters as attributes. The electronic parameters were obtained through first-principles calculations. This model is highly effective in estimating transition energy values for various Ce3+-doped garnet-type oxides. The machine learning model improved the accuracy of transition energy calculations. Furthermore, we have developed predictive models that estimate first-principles calculation results based on structural data. Systematic first-principles calculations of fictitious garnet-type oxides with gradually changed structural parameters were performed and used as the training data. The predictive models of the electronic parameters such as the bond order, the crystal field splitting (εcfs) and the net charge were used to create a two-step predictive model based solely on structural parameters.
Charge Transfer Luminescence of LiCa3MgV3O12 and LiCa3ZnV3O12 Under Ionizing Radiation Excitation
Authors: Kawaguchi Noriaki , Okazaki Kai , Kato Takumi , Nakauchi Daisuke , Yanagida Takayuki
Published: December 2024

A scintillator is a material that generates a large number of excited electrons and holes under ionizing radiation excitation and immediately emits light with recombination of electrons and holes. When a scintillator combined with a photodetector, it is used as a radiation detector. Radiation detectors equipped with scintillators are applied in various fields such as medical care, security, and radiation protection. Researches are still being conducted to find novel materials with higher performance. In particular, we are attracted to compounds containing lithium (Li). This is because the Li isotope 6Li causes a nuclear reaction with neutrons, so Li-containing materials could be used as neutron scintillators. The Ce-doped lithium silicate glass (lithium glass) and the Eu-doped LiI single crystal are known as conventional Li-containing scintillators; however, the segregation of dopants in these materials can be a problem. For example, the lithium glass can be divided into areas with high and low emission intensity by the dopant segregation. It causes a double-peak in the pulse height spectra under neutron irradiation, and measurement accuracy will deteriorate.

In this study, we focused on LiCa3MgV3O12 and LiCa3ZnV3O12 as candidates for scintillators that contain Li and do not require dopants. The photoluminescence properties of powder samples of LiCa3MgV3O12 and LiCa3ZnV3O12 have already been reported; however, scintillation properties have not yet been investigated. We prepared the sintered ceramics of LiCa3MgV3O12 and LiCa3ZnV3O12 and evaluated their scintillation properties. High-purity powders of Li2CO3, CaO, MgO, ZnO, and V2O5 were used as raw materials. They were weighed in stoichiometric proportions and ground using aluminum mortar and pestle, and then calcined at 750℃ for 6 hours in aluminum crucibles. The obtained powders were ground again, pressed into pellets, and then sintered at 850℃ for 6 hours. The X-ray diffraction (XRD) patterns of the samples were measured and compared with those in the previous literature, and we confirmed that each of them had a single phase. In the X-ray induced scintillation spectra, broad luminescence peaking at around 500 nm was observed in each sample. Both emissions can be explained by the charge transfer transition between V5+–O2-.
Prediction of Emission Energy of d3 Ions in Oxides Based on Local Structures Using First-Principles Calculations and Machine Learning
Authors: Kimura Fumiya , Tanaka Shuma , Ogasawara Kazuyoshi
Published: December 2024

Red phosphors activated with Mn4+ are attracting attention as potential phosphor materials that can improve the color rendering properties of white LEDs. However, since Mn4+: KSF which is currently in practical use is unstable and toxic, a special surface treatment is required in actual usage. Therefore, in order to theoretically design stable and inexpensive red phosphors, we focused on oxide phosphors activated with Mn4+ and other d3 ions. Since emission energies of Mn4+ in oxides are always lower than the desired value, it is important to explore local structures which realize higher emission energies. For this purpose, we have recently created emission energy maps based on local structures using systematic first-principles calculations for CrO6 and MnO6 clusters with D4h and C4v symmetries. In this work, in order to investigate the influence of the ionic species, we created the emission energy maps of the other d3 ions such as V2+ and Fe5+. We constructed VO6 clusters and FeO6 clusters with gradually changed local structures and performed systematic first-principles calculations using the DV-Xα method and the DVME method. The emission energy maps of VO6 and FeO6 based on local structures were created and compared to those of CrO6 and MnO6. By using the obtained multiplet energies as the training data, we also created predictive models of emission energies of d3 ions in oxides by machine learning.
Constructing Point-of-Care Diagnostics: Developing New Chemistry for the Functionalization and Use of High-Density Microelectrode Arrays
Authors: Moeller Kevin D
Published: December 2024

The detection of infectious pathogens at the point-of-care remains a challenging task due to the need to detect a series of at times closely related metabolites in locations that are often remote from a major medical center. High density microelectrode arrays have the potential to serve as an effective tool to address these issues because they contain thousands of individually addressable electrodes that can each be selectively functionalized with a specific molecular recognition element. New surfaces for the arrays have lifetimes of over a year, allow for the multiplex detection of small molecules, and are compatible with urine-based samples.

However, the systems developed to date are not yet ideal. While the surfaces are stable, they are not always uniform. The mediators used for the analytical experiments are themselves not always compatible with a point-of-care application, and while the experiments are fundamentally compatible with urine, urine samples vary greatly and it is not clear exactly how general those experiments are. At the same time, arrays for this specific application are functionalize using Cu(II)-mediated cross coupling reactions. But, how good are those reactions? We know that they allow for selective placement exclusively at a targeted electrode or set of electrodes in an array, but what is the yield of such a process? Can the reactions be used to build a molecular library directly on a microelectrode array?

In this presentation, we will present answers to these questions along with a look at the general strategies being used to acquire those answers. In so doing, we hope to illustrate how a synthetic/ physical organic chemistry approach to the problem can present new solutions that are helping to bridge the gap between the idea of a point-of-care device and an actual working prototype.
Electrochemical Oxidation of Xylitol on Ag to Valuable Organic Acids: Mechanistic Study and Product Analysis
Authors: Tran David , Meng Zhe , Kristoffersen Henrik Høgh , Rossmeisl Jan , Hjelm Johan
Published: December 2024

Switching from a non-renewable fossil-based economy to a bioeconomy relying on biomass utilisation is one of the key challenges to achieving a change towards sustainable chemical production. Biomass offers a wide variety of valuable components such as lignin, (hemi)celluloses, other (poly)saccharides, and proteins that could be used to produce biobased bulk, fine and speciality chemicals, polymers and transportation fuels. Xylitol is one of the high-value-added biomass-derived compounds that is used in the food and pharmaceutical industries and can act as a platform for the chemical synthesis of other high-value compounds like ethylene- and propylene glycol.1

The electrochemical oxidation of polyols such as glycerol, sorbitol and xylitol in alkaline media has been studied mechanistically and to determine their suitability for applications in alcohol fuel cells.2,3 Investigations with glycerol have revealed two main reaction pathways: The full oxidation to glyceric acid with subsequent C-C cleavage to glycolic and formic acid or the alkaline-driven elimination and rearrangement of glyceraldehyde to lactic acid. However, mechanistic investigation and product analysis are under-explored for the electrochemical xylitol conversion.

Here, we investigate the potential-controlled bulk electrolysis of xylitol in alkaline media on Ag in a divided cell setup to analyze the product outcome at various constant potentials and xylitol concentrations. The reaction progress is monitored with NMR spectroscopy, followed by HPLC analysis. Glycolic (GCA) and formic acid (FA) are the main products, showing the cleavage of xylitol upon oxidation and the same selectivity as glycerol. We hypothesize the formation of either xylose or xylulose as an intermediate, and both exhibit a different cleavage behaviour upon further oxidation as displayed in figure 1. Erythrose and glyceraldehyde further react to GCA and FA. Moreover, the variation of electrolysis potential and concentration shows only minor changes in the product distribution, and no signs of poisoning are visible at prolonged reaction time. This makes Ag-based electrodes a promising material for the complete conversion of xylitol to obtain biomass-derived small organic acids.

1. J. Sun, H. Liu, Green Chem., 2011, 13, 135.

2. Y. Kwon, K. J. P. Schouten, M.T.M. Koper, ChemCatChem.,
2011, 3, 1176.

3. L.J. Torres-Pacheco, A. De Leon-Rodriguez, L. Álvarez-Contreras, M. Guerra Balcázar, N. Arjona,
Electrochim. Acta, 2020, 353, 136593.

4. Z. Meng, D. Tran, J. Hjelm, H. H. Kristofferson, J. Rossmeisl, ACS Catal., 2024, 14, 4, 2455.

Figure 1
Visible-Light Induced C-H Oxygenation of Hydrocarbons Using Chlorine Dioxide as a Photoredox Catalyst
Authors: Ohkubo Kei
Published: December 2024

Photocatalytic oxygenation of benzene occurs in an oxygen-saturated acetonitrile solution containing acridnium ion or quinolinium ion derivatives as a photoredox catalyst, benzene and water under light irradiation to yield phenol and hydrogen peroxide selectively. The benzene radical cation, which is formed by photoinduced one-electron oxidation of benzene with the excited state of catalyst, reacts with H2O to yield phenol.

Photocatalytic oxygenation of benzene with oxygen occurs under photoirradiation of an acetonitrile solution of 3-cyano-1-methylquinolinium perchlorate (QuCN+ClO4
–) in an oxygen-saturated acetonitrile (MeCN) containing benzene and H2O with a xenon lamp (500 W) attached with a color-cut glass filter. The selectivity of formation of phenol was 98% with 16% quantum yield after 1 h irradiation, and then 51% of phenol yield after 5 h irradiation. The photocatalytic turnover number (TON) was 7.5. This is the first example of photocatalytic oxygenation of benzene to phenol in a homogeneous system. A preparative gram-scale photocatalytic reaction with benzene (2.3 g, 29 mmol) and QuCN+ (210 mg, 0.8 mmol) in MeCN (200 mL) for 48 h was also examined to afford phenol (1.1 g, 12 mmol) as 41% yield.
The Effect of Adding Glycerol in Hydrogen Production Using AEM Reactor
Authors: Tateno Hiroyuki , Chen Shih-Yuan , Horiguchi Genki , Mochizuki Takehisa
Published: December 2024

Abstract: Anion exchange membrane (AEM) reactor is a promising technology for cost-effective hydrogen production because it can use cheap non-precious metals due to its alkaline conditions. On the other hand, the utilization of glycerol, a by-product in biodiesel fuel (BDF) production, is one of the important subjects for decreasing waste. In recent years, electrochemically utilization of glycerol has attracted wide attention due to its lower oxidation potential than H2O. In this work, using an AEM reactor, we investigated the effect of adding glycerol on the integrated production of high-value-added products from glycerol and hydrogen with low energy consumption.
(Invited) Synthetic Electrochemistry: Leaping into a New Era
Authors: Kawamata Yu
Published: December 2024

Electrochemistry plays a pivotal role in organic synthesis, offering efficient and sustainable pathways for the construction of complex molecules. By harnessing the power of electricity, precise and unique redox reactions are possible, facilitating the synthesis of diverse organic compounds with high selectivity and atom economy. The merger of this technique with radical coupling offers unrivalled synthetic utility under mild and practical conditions. In this lecture, our recent development of electrochemical coupling reactions as well as how they are changing the landscape of organic synthesis will be discussed.
Non-Native Bioelectrocatalytic C-C and C-N Bond Formation via Cobalamin Dependent Enzymes
Authors: Kays Luke , Boucher Dylan G. , Kumar Amardeep , Gupta Paras , Lewis Jared , Minteer Shelley D.
Published: December 2024

Bioelectrocatalysis involves the use of biomaterials to catalyze redox reactions at an electrode. Biocatalysis offers improved selectivity and typically involves milder reaction conditions, while electrocatalysis can involve the use of renewable energy as an electron source. Cobalamin (B12) dependent enzymes catalyze C-C and C-N bond forming reactions via radical mechanisms through the formation of a Co(III)-alkyl intermediate. Homolysis of the Co(III)-C bond leads to radical coupling with various substrates to form the product. However, these alkyl radicals can react through a variety of mechanistic pathways, leading to a mixture of products. Controlling the alkyl radical intermediate would lead to improved reaction selectivity.

Here, we report on CarH*, an engineered variant of a B12 dependent photoreceptor protein, which catalyzes styrene C-H alkylation by trapping an alkyl radical intermediate in its protein scaffold. The reversible Co-alkyl bond homolysis protects the radical, allowing for selective olefin addition. However, to initiate this reactivity, the cobalt center of CarH* must be reduced through stoichiometric addition of the reducing agent titanium (III) citrate. Thus, we are developing a mediated electrochemical system to achieve this transformation without the use of a stoichiometric reductant and to investigate new reactivity in CarH* and similar variants. A diffusive redox mediator was found to deliver electrons to CarH* and drive alkyl radical formation. This methodology offers a more sustainable and general approach to electrochemical non-native biocatalysis and can be applied to discover new reactivity in B12 dependent enzymes.