bluuebunny/crossref_metadata_2025 huggingface dataset:
Rational Design of Phase-Engineered WS2/WSe2 Heterostructures By Low-Temperature Plasma-Assisted Sulphurization and Selenization Toward Enhanced HER Performance
Authors: Rehman Bushra , Chueh Yu-Lun , Kimbulapitiya K.M.M.D.K , Peng Yu-Ren
Published: December 2024

The efficient hydrogen generation from water splitting underpins chemistry to realize the hydrogen economy. The electrocatalytic activity can be effectively modified by two-dimensional (2D) heterostructures, which offer great flexibility. Furthermore, they are useful in enhancing the exposure of the active sites for the hydrogen evolution reaction. Although the 1T metallic phase of the Transition Metal Dichalcogenides (TMDs) is important for the hydrogen evolution reaction (HER) catalyst, its practical application has not yet been much utilized because of the lack of stability of the 1T phase. Here, we introduce a novel approach to create a 1T-WS2/1T-WSe2 heterostructure using a low-temperature plasma-assisted chemical vapor reaction (PACVR), namely plasma-assisted sulphurization and plasma-assisted selenization processes. This heterostructure exhibits superior electrocatalytic performance due to the presence of the metallic 1T phase and the beneficial synergistic effect at the interface, which is attributed to the transfer of electrons from the underlying WS2 layer to the overlying WSe2 layer. The WS2/WSe2 heterostructured catalyst demonstrates remarkable performance in HER, as evidenced by its small Tafel slope of 57 mV.dec–1 and exceptional durability. The usage of plasma helps in replacing the top S atoms with Se atoms, and this ion bombardment also increases the roughness of the thin film, thus adding another factor to enhance the HER performance. This plasma-synthesized low-temperature metallic phase heterostructure brings out a novel method for the discovery of other catalysts.

Keywords: TMDCs, PACVR, WS2, WSe2, HER.

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(Invited) Hot Electron Photodetectors, Sensors and Solar-Cells
Authors: Nunzi jean-Michel , Poushimin Rana
Published: December 2024

Plasmonic nanostructures can generate energetic “hot” electrons from light in a broad band fashion depending on their shape, size, and arrangement. These nanostructures have a promising use in photodetectors, allowing high speed, broad band, multicolor and polarized photodetection. Because they function without a band-to-band transition, photon detection at any energy is possible through engineering of the plasmonic nanostructure. Compact hot-electron-based photodetectors that combine polarization sensitivity and light detection in the near-infrared region were fabricated using an indium tin oxide (ITO)−gold hybrid layer.[1] Sensitivity of the device was significantly increased by use of self-assembled monolayers in a capacitor configuration. The resulting devices are capable of detecting light below the ITO band gap at ambient temperature without any bias voltage. The devices can also function as photovoltaic solar cells using an electrolyte which provides charge transport to the electrodes (Fig 1).[2] Interestingly the surface sensitivity of the hot electron emission effect can be used for femtomole sensitivity.

Figure 1: current voltage characteristic under 1 sun AM 1.5 solar simulation of an array of gold nano-antenna cathode hot-electron emission dye-sensitized-like solar cell.

References:

[1] ‘Simple Unbiased Hot-electron Polarization-sensitive Near-Infrared Photo-detector’, S.M.A. Mirzaee, O. Lebel, J.M. Nunzi, ACS Appl.Mater.Inter. 10, 11862-11871 (2018)

[2] ‘Requirements for a rectifying antenna solar cell technology”, J.M. Nunzi, Proc SPIE 7712, 771204 (2010).

Figure 1
(Invited) the Future of MOFs - Asking the Question - "What Needs to be True?"
Authors: Miller Stuart Raymond
Published: December 2024

The urgent need to decarbonize society to combat climate change has spurred significant interest in developing new materials capable of directly or indirectly reducing our global carbon footprint through technologies including carbon capture, electrolysis and novel energy storage systems.

Over the last 25 years, Metal-Organic Frameworks (MOFs) have gained significant attention owing to their potential in fields of gas adsorption, separation and energy storage. However an extremely limited number of MOFs have demonstrated commercial success. This presentation will ask the question why MOFs have not been more industrially successful and why the 2015 Paris Agreement offers opportunities uniquely suitable for MOFs. Challenges such as scalability, cost, and integration with existing infrastructures will be discussed, alongside the potential environmental impacts of new material production.

This presentation will introduce Underwriters Laboratories Research Institutes newest institute, the Materials Discovery Research Institute (MDRI) which leverages a computational and theoretical approach to target materials designed to specific applications coupled with advanced automated synthesis methodologies and an entirely digital Laboratory Information Management System.
Ordered Transfer from 3D-Oriented MOF Superstructures to Polymeric Films and Patterns
Authors: Falcaro Paolo , Brandner Lea
Published: December 2024

Three-dimensional oriented metal-organic frameworks, or 3D-oriented MOFs, feature precisely arranged pores that extend over large areas. This order is essential for enhancing directed diffusion and arranging functional guest species within the oriented pore channels. [1] For example, pore orientation in porous MOF matrices is desired for photonics and ion conductivity uses.[2] Yet, 3D-oriented MOF films and patterns can rapidly decompose in the presence of moisture and acidic environments. [3] This propensity to degradation limits their applicability.

Here, by starting with MOF films that are N3-functionalized and heteroepitaxially aligned, we promote the formation of an oriented polymeric film. With X-ray lithography, we target the azide groups for selective degradation thus enabling the crosslink in defined regions: this fabrication process enables the preparation of porous polymeric patterns. The water-stable porous polymer patterns showed unique fluorescent behaviour when exposed to polarized light, which holds promise for advancing optical and photonic devices. [4]

References

[1] M. Linares‐Moreau, L. A Brandner, M. de J Velásquez‐Hernández, J. Fonseca, Y. Benseghir, J.M. Chin, D. Maspoch, C. Doonan, P. Falcaro Adv.Mater.
2024, 36, 2309645

[2] M.d.J. Velásquez-Hernández, M. Linares-Moreau, L.A. Brandner, B. Marmiroli, M. Barella, G.P. Acuna, S.D, Zilio, M.F.K. Verstreken, D.E. Kravchenko, O.M. Linder-Patton, J.D. Evans, H. Wiltsche, F. Carraro, H. Wolinski, R. Ameloot, C. Doonan and P. Falcaro. Adv.Mater.
2023, 35, 2211478.

[3] L.A Brandner, M. Linares-Moreau, G. Zhou, H. Amenitsch, S. Dal Zilio, Z. Huang, C. Doonan, P. Falcaro Chem.Sci.,
2023, 14, 12056.

[4] L.A. Brandner, B. Marmiroli, M. Linares-Moreau, M. Barella, B. Abbasgholi-NA, M.de J. Velásquez-Hernández, K. L. Flint, S.Dal Zilio, G. P. Acuna, H. Wolinski, C. J. Doonan, P. Falcaro, Submitted.
(Invited) open the Gate: Molecular Dynamics Simulation of Adsorption-Induced Phase Transformations of MOF Nanocrystallites
Authors: Schmid Rochus
Published: December 2024

One of the most intriguing features of Metal-organic frameworks (MOFs) is their ability to respond to external stimuli, like the adsorption of guest molecules, with large changes in the accessible pore volume. Theoretical simulations are a key tool to understand such “gate opening” processes on a molecular level. This is typically done within the approximation of periodic boundary conditions (PBC) and using Grand Canonical methods. Such simulations exclude, however, the interface between the MOF and the gas reservoir and ignore any transport effects, which limits them to the thermodynamic equilibrium. Especially for sensing applications, the kinetics of such processes can become important. Recently, our group started to develop and apply methods to simulate MOF nanocrystallites (NCs) beyond PBC, to circumvent such limitations [1,2,3].

In the presentation, recent results on the pore opening of DUT-8(Zn) nanocrystallites in carbon dioxide will be shown. Unbiased molecular dynamics simulations reveal a rather fast phase transformation within a few nanoseconds. The first-order phase transition is initiated by a characteristic pore opening at a corner of the crystallite. The anisotropy of the pillared-layer MOF with its channels along the crystallographic c-axis leads to a specific transport pattern for the guest molecules when the pore opening of the MOF proceeds. The simulations allow an unprecedented view of the actual process, including both the mechanics of the phase transformation of the MOF and the diffusive transport of the guest molecules from the reservoir into the MOF.

[1] J. Keupp, R. Schmid, Adv. Theory Simul. 2019, 2, 1900117.

[2] L. Schaper, J. Keupp, R. Schmid, Front. Chem. 2021, 9, 757680.

[3] L. Schaper, R. Schmid, Commun. Chem. 2023, 6, 233.
Recent Progress in Modeling Thermal Transport in MOFs
Authors: Wilmer Christopher
Published: December 2024

In this presentation we report on recent simulation studies on the thermal transport properties of MOFs. Having recently completed a large-scale screening study of MOFs where we determined structure-property relationships related to thermal conductivity, we are now interested in finding combinations of factors that can lead to fast heat conduction in MOFs. Factors we will discuss in the presentation include flexibility, interpenetration, surface area, void fraction, interaction potentials, and defects.
(Invited) the Use of Metal-Organic Frameworks in Adsorption Cooling/Heating: From the Perspective of Computational Screening
Authors: Li Song , Li Wei , Liu Zhilu
Published: December 2024

With the severe climate change, there is a growing energy demand for cooling and heating, which takes up 20% of the global energy consumption. Adsorption cooling/heating driven by low-grade heat sources including waste heat and solar energy has been a promising alternative owing to its reduced electricity consumption, low carbon emission and easy operation. However, the coefficient of performance for cooling/heating (COPC/ COPH) and specific cooling/heating effects(SCE/SHE) is still unsatisfactory due to the low uptake and high regeneration cost of conventional adsorbents such as activated carbon and zeolites. Metal-organic frameworks (MOFs) have been recognized as the potential adsorbents for adsorption cooling/heating due to their outstanding adsorption capacity resulted from ultrahigh surface area. Nevertheless, given the huge number of MOFs, it is a challenging task to quickly identify the potential candidates. Besides, the relationship between structure properties, adsorption behaviors and the cooling/heating performance is still elusive. In this study, high-throughput computational screening strategy based on integrated grand canonical Monte Carlo (GCMC) simulation and numerical simulation for efficiently evaluating the cooling/heating performance of a large number of MOFs was developed for both alcohol and water working fluids. The extracted structure-performance relationship highlighted the importance of both structure properties of MOFs and their adsorption characteristics. Machine learning algorithm was also carried out to accelerate the cooling/heating performance prediction of MOFs. To be consistent with experimental measurement, the adsorption dynamics was also taken into consideration. Multiscale modeling combining the molecular simulation and the mathematical simulation was proposed to obtain the COP and specific cooling power (SCP) for a vast number of MOF-based working pairs with high efficiency. This study provides the theoretical approaches to quickly identify high-efficient MOF adsorbents for high-performing adsorption cooling/heating.
Effect of Concentration and Addition Timing of Bromide Ion on Synthesis of Thin Silver Nanowires (AgNW)
Authors: Shimizu Keiya , Aoki Atsushi
Published: December 2024

Indium tin oxide (ITO), currently widely used as a transparent conductive material to OLED, solar cells and EC devices, has advantages such as low sheet resistance and high transmittance, but it has defects such as inflexibility, fragility and vacuum process production. Alternative transparent conductive materials are required to replace ITO. Silver nanowires (AgNW) have one of attractive attention because AgNW dispersed films show low sheet resistance and high transparency, and even more excellent flexibility, and solution process production. However, the current AgNW films have higher resistance than that of ITO because diameter of AgNW is sub mm order and poor formation of two-dimensional network of AgNW. Therefore, we aimed to reduce the resistance of AgNW film by thinning diameter of AgNW, which is expected to improve conductivity by increasing number of AgNW while maintaining transparency.

Synthesis thinning diameter of AgNW was performed by a polyol reduction method using polyvinylpyrrolidone (PVP) and Br- ion as capping agents, and Ag+ ion was reduced to Ag metal by thermal decomposition of ethylene glycol. As PVP and Br- ion are selectively adsorbed on Ag(100) plane, Ag(111) plane grew, resulting in AgNW production. The reactant solution including NaCl, NaBr, PVP, and AgNO3 in ethylene glycol was heated to 130 ˚C to synthesize AgNW. Br- ion was first added before heating, and the synthesis was carried out at NaBr concentrations ranging from 0 µM to 59.8 µM. As a result, AgNW production was confirmed at the low NaBr concentrations below 53.1 µM, but thin AgNW was not observed. At the high NaBr concentration above 53.1 µM, no AgNW synthesis was observed because Br- ion inhibited the growth of AgNW.

Next, we examined the timing of addition of Br- ion at the NaBr concentration of 53.1 µM. When excess Br- ion was added before heating, we supposed that it would inhibit the formation of AgCl nuclei and prevent AgNW growth. When Br- ion was added within 1 hour after the start of heating, the growth of AgNW was inhibited by Br- ion and the synthesis of AgNW could not be confirmed as same as the case of NaBr addition before heating. Addition of Br- ion over 1 hour after the start of heating did not also result in the formation of thin AgNW because the growth of thick AgNW had already been completed. By addition of Br- ion at 1 hour after the start of heating, the formation of thin AgNW was observed.

The crude dispersed AgNW solution was diluted in ethanol and then stood for several hours to precipitate thick AgNW. The supernatant solution was pipetted and thin AgNW was precipitated by adding acetone to remove ethylene glycol. The purified thin AgNW were deposited on glass slides by the spray-coating method. Annealing of the deposited substrate at 130 ˚C was used to confirm the decrease in resistance. As a result of resistance measurement, a sheet resistance of 34.6 Ω/sq was achieved at 90% transmittance, and the transparent conductive material was successfully fabricated.
Synergistic Effects of Co-Doping WO3 with Al and Pt on Photoelectrochromic Performance
Authors: Okwako Jacinta , Han Chi Hwan
Published: December 2024

In this work, a detailed study has been carried out to understand the photoelectrochromic properties of tungsten oxide (WO3) co-doped with Al and Pt. Similarly, the photoelectrochromic findings are supported by material characterization, providing additional understanding of the photoelectrochromic performance exhibited by the prepared samples. In addition, the effects of Al and Pt doping on photoelectrochromic performance are discussed in detail with focus on X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with EDS, X-ray photoelectron spectroscopy (XPS), and optical transmittance. XRD peaks confirmed the presence of hexagonally-structured WO3 in the prepared samples with polycrystalline nature and a similar observation was confirmed via TEM analysis. Surface characterizations conducted through SEM and EDS analyses unveiled the morphologies and particle sizes. Optical studies showed a bandgap of 1.88 eV and 1.95 eV for Al doped and Al-Pt co-doped WO3, indicating bandgap shrinkage in comparison to the optical bandgap of WO3 of 2.36 eV. The Al-Pt co-doping resulted in a significant enhancement in photoelectrochromic performance, attaining an optical modulation of 43.61% at 550 nm and consequently 85% of the initial transmittance recovered after 2 hrs of bleaching in the dark. This was an improvement in comparison to the Al doped sample which attained a coloration depth of 43.15% at 550 nm with only 75% of the original transmittance being recovered after 2 hrs under dark conditions.

Key Words: Tungsten Oxide, Co-doping, Smart Window, Charge Transfer
High-Entropy Electrocatalysts for Seawater Splitting
Authors: Hung Wei Hsuan , Chiang Ching-Yu , Chiu I-Chia , Chang Hsin-Ya
Published: December 2024

Due to the consumption of primary energy, the demand for renewable energy is increasing. Because of its high energy density and zero carbon emissions, water electrolysis to produce hydrogen is an ideal and clean energy choice. However, fresh water is a high demand resource for people's livelihood which only takes less 3 percent in the full water resource. Therefore, exploring the use of seawater, which accounts for over 70% of the earth, as a source for seawater splitting is worthwhile. We need to find a more efficient and long-last catalyst to avoid the chorine evolution, a competition reaction during oxygen evolution (OER), causing the corrosion process to suppress the life span of catalyst for usage of the seawater to produce hydrogen. High entropy materials, a potential promising catalyst candidate, due to their tunable electronic structures leading to a much lower OER overpotential and corrosion resistance. In this work. we use a pulsed laser irradiation scanning on mixed salt solutions (PLMS) method to produce a six elements high entropy ceramic nanoparticles as OER catalyst for efficient and stable work in seawater environments. The (AlCoCrFeMnNi)O high-entropy ceramic (HEC) we proposed demonstrate a great performance in the seawater environment. The onset voltage of oxygen-evolution can low down to 1.47V vs. RHE, and in terms of stability our catalyst is capable to operate for 1000 hours under 100mA/cm2. Furthermore, to understand the mechanism behind our (AlCoCrFeMnNi)O HEC, the in-situ XAS (X-ray absorption spectroscopy) measurement and In-situ EXAFS are carried out in this work under different OER voltage applied. Co, Mn, and Ni identified as the active sites of OER and these three elements work intimately together with each different reaction routes, including the adsorbate evolution mechanism (AEM) and lattice oxygen-participated mechanism (LOM). While Al, Cr, and Fe are not directly contributed to the catalytic activity but they play important roles to stabilize the high entropy structure during the whole reaction.

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Preparation of Freestanding Films Using Barium Titanate Nanoparticles and Their Electrical and Optical Properties
Authors: Takashima Hiroshi , Katsumata Tetsuhiro , Takebayashi Yoshihiro , Ono Takumi , Sue Kiwamu
Published: December 2024

BaTiO3 ferroelectric perovskites have been applied to a variety of applications, including multilayer ceramic capacitors (MLCC), piezoelectric transducers, actuators, thermistors with positive temperature coefficient, and ultrasonic devices. In the development of MLCC manufacturing processes, understanding the relationship between the particle size and structure of barium titanate material particles, the phase transition temperature to the ferroelectric phase, and dielectric properties is very important for understanding the design and transformation of the material particles. We have studied the evaluation of phase transition temperatures using X-ray diffraction and SHG analysis.In this study, barium titanate nanoparticles with a diameter of approximately 50 nm were used to formulate a paste by mixing with solvents and resins. The production method was modeled on the already commercialized Ag paste method. After screen printing, the paste was heat-treated at 110°C to solidify to form a freestanding film. The creation of freestanding films allows for easy control of film thickness without the influence of the substrate, which is expected to expand the range of applications. After further heat treatment at over 1000°C, Pt electrodes were formed on both sides of the film by sputtering, and the dielectric constant and its temperature change were evaluated as a parallel plate capacitor. Typical film thickness is 200 μm. As a result, it was found that the dielectric constant was higher than that of the bulk material, with a maximum value around 120°C. The loss was found to be very small, less than 0.05. These results indicate that the material is highly practical. XRD results also confirmed the existence of a phase transition temperature around 120°C. Furthermore, SHG results also corroborate the XRD results. Details of the paste preparation method, freestanding films, evaluation by cross-sectional SEM after heat treatment, temperature dependence of dielectric properties, and evaluated nanoparticle properties will be discussed.
Dual-Vacancy-Engineered ZnIn2S4 Nanosheets for Harnessing Low-Frequency Vibration Induced Piezoelectric Polarization Coupled with Static Dipole Field to Enhance Photocatalytic H2 Evolution
Authors: Tian Hong-Kang , Hung Ming-Yuan , Kuo Yen-Ting , Wu Jih-Jen
Published: December 2024

This study delves into the realm of chemically complex materials, focusing on Zinc Indium Sulfide (ZnIn2S4, ZIS) for efficient photocatalytic water splitting into hydrogen (H2) and oxygen (H2). Recognizing the pivotal role of microstructures in chemically complex materials, our research emphasizes the impact of defects in ZIS, a material with multiple principal chemical components, on its H2 production efficiency. We explore the optimization of material defects, particularly sulfur (S) and indium (In) vacancies, under external stress to enhance H2 production through dipole and piezoelectric effects. To unravel the intricate process-structure-property relationships in ZIS, we utilize a multi-scale computational approach. Density Functional Theory (DFT) is employed to calculate dipole moment, dielectric, elastic, and piezoelectric properties under varying defect compositions. These properties are then integrated into a continuum model developed through Finite Element Analysis (FEA), bridging mechanical and electrical phenomena to simulate the electric potential distribution (voltage) in both pristine and defective ZIS. Our simulations demonstrate a marked increase in voltage, induced by internal dipole moments and piezoelectric effects, especially pronounced along the (100) and (010) crystal orientations in defective ZIS. This enhanced voltage leads to improved charge separation, substantially increasing the H2 production rate upon electron excitation and generation of electron/hole pairs. Our findings contribute vital insights into the microstructural influences on the photocatalytic performance of ZIS, offering design principles for advanced materials in renewable energy applications. This study exemplifies the power of computational techniques in elucidating the complex interplay between microstructure and properties in chemically complex materials, aligning with the core focus of this symposium.

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Sulfide Catalysts Anchored on Graphene As an Efficient Sulfur Host for Lithium-Sulfur Batteries
Authors: Chuang Yu-Wei , Yeh Che-Ning
Published: December 2024

Lithium sulfur batteries (Li-S batteries) have emerged as a promising candidate for next-generation energy storage systems owing to their superior theoretical energy density and cost effectiveness. However, the serious shuttle effect of soluble polysulfides and low sulfur loading have hindered their commercialization. To alleviate the polysulfide shuttle, various polar materials have been introduced and investigated in batteries. Despite the strong polysulfide adsorption ability and catalytic effect, the high density and low specific surface area of polar metal compounds have made the realization of high sulfur loading challenging. Therefore, rational design of a polar sulfur host with high specific surface area is crucial for practical application of Li-S batteries. In this work, transition metal sulfides are selected as polysulfide immobilizers due to their good conductivity and sulfiphilic property, enabling effective polysulfides capture and conversion. Sulfide nanoparticles derived from layered double hydroxides (LDHs) are uniformly anchored on reduced graphene oxide sheets through a simple two-step hydrothermal process. Owing to the high specific surface area of LDH and graphene, this composite material offers abundant active sites to effectively trap soluble polysulfides under high sulfur loading conditions. In addition, the uniformly dispersed binary metal sulfide exhibits better catalytic activity for polysulfide conversion compared to single-component sulfides. Therefore, employing this material as a sulfur host enables Li-S batteries with high sulfur loading, which deliver remarkable cycle stability and electrochemical performance. This work presents a promising approach for achieving high sulfur loading through the combination of polar and carbon materials.
NiMn-Layered Double Hydroxides@Metal Anchored Nitrogen-Doped Carbon Framework As a Bifunctional Catalyst for Rechargeable Zinc-Air Batteries
Authors: Tu Ko-Fan , Yeh Che-Ning
Published: December 2024

The rechargeable zinc-air battery (ZAB) holds promise as an energy storage system for the next generation due to its high theoretical energy density, safe aqueous electrolyte, environmental friendliness, and cost-effectiveness of zinc. However, the efficiency of ZABs is hindered by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Noble metals such as platinum (Pt), iridium dioxide (IrO2), and ruthenium oxide (RuO2) are commonly used as advanced electrocatalyst materials. Nonetheless, their scarcity, high cost, unstable catalytic properties, and susceptibility to carbon monoxide poisoning limit the large-scale applications of ZABs.

Therefore, exploring non-noble bifunctional electrocatalysts for ZABs is crucial, with transition metals being viable alternatives. Recently, bimetallic transition metal layered double hydroxide (LDH) has emerged as a promising candidate for OER catalysts due to its high specific surface area, abundant active sites, and synergistic effects between two transition metals. However, LDH still faces challenges such as poor electrical conductivity and self-aggregation during fabrication.

In this work, we developed a three-dimensional core-shell structure, enabling the growth of LDH on nitrogen-doped porous carbon framework (N-C) materials to address these challenges. The N-C material, derived from zeolitic-imidazole framework (ZIF) material after pyrolysis, shows promise as an ORR catalyst. ZIF, a subclass of metal-organic framework (MOF), boasts high nitrogen content and inherits MOF advantages such as a high surface area, abundant active sites, and chemical stability. Furthermore, utilizing mesoporous silica as a hard template allows us to maintain the dodecahedral structure of ZIF and create mesoporous structures after annealing.

The core-shell structure developed in this study demonstrates superior OER and ORR catalytic activity, offering a promising direction for the design of bifunctional catalysts for high-performance ZABs.
2D/3D Heterojunction Perovskite Devices with Controlled Order and Orientation
Authors: Yeh Cheng-Hsien , Shih Chuan-Feng , Hsiao Yuan-Wen , Huang Yu-Hui , Wu Hsuan-Ta , Leu Ching-Chich
Published: December 2024

This research demonstrates 2D/3D heterojunction perovskite devices with controlled order and orientation. First, a state-of-the-art vertical-transport photodetector with a n-type three-dimensional (3D) MAPbI3/p-type quasi-two-dimensional (Q-2D) perovskite heterojunction. This structure introduces a built-in electric field at the n-p junction that greatly improves the characteristics of the perovskite photodetector, and the presence of Q-2D perovskite on the surface much improves the life. The electrical polarities of the 3D and the Q-2D perovskite layers are simply controlled by self-constituent doping, making clearly defined n-p characteristics. Doctor-blade coating is used to fabricate the photodetector with a large area. The Q-2D materials with highly oriented (040) Q-2D (n = 2, 3) planes are near the surface, and the (111) preferred planes mixed with high index Q-2D materials (n = 4, 5) are found near the 3D/Q-2D interface. The stacking and interface are beneficial for the carrier extraction and transport, yielding excellent perovskite photodetectors. Secondly, solvent engineering, anti-solvent engineering and annealing process were used here to control the crystal orientation of 2D perovskite, and successfully form a novel vertical/horizontal (2D/2D) stacked bilayer heterogeneous structure by the introduction of a thin BAI layer. The device exhibits significant bipolar switching characteristics, stable resistance distribution, high switching ratio (106), long retention time (104 s) and outstanding endurance (~4,000 cycles).
Temperature and Interface Trap Effects on Hydrogen-Terminated Diamond Metal-Oxide Field-Effect Transistor (HD-MOSFET) Using Tcad Sentaurus
Authors: Alshammari Nuwayyir , Maimon Ory , Mulpuri Rao V , Li Qiliang
Published: December 2024

Wide and ultrawide bandgap semiconductors demonstrate exceptional performance due to their large energy bandgap, which offers distinctive advantages such as enhanced efficiency, drift velocity, increased voltage blocking, and high-frequency switching. These characteristics make such semiconductors essential for advancing electronic technology. Among such materials, diamond is particularly distinguished for its wide bandgap, superior thermal conductivity, and high electron mobility. These properties enable diamond to perform exceptionally well in challenging environments where traditional materials may fail. Additionally, its ability to operate at elevated temperatures and voltages renders diamond-based devices suitable for a range of applications, including high-power electronics and high-frequency RF systems.

The hydrogen-terminated Metal-Oxide Field Effect Transistor (HD-MOSFET) is a highly promising and widely studied diamond device. In this device, hydrogen termination is used to induce a two-dimensional hole gas (2DHG) as high as 1014 cm-2, resulting in high drain current.

Our study investigates the Hydrogen-Terminated Diamond Metal-Oxide Field-Effect Transistor (HD-MOSFET) using TCAD Sentaurus to gain insights into the thermal performance and operational limits of diamond-based semiconductor devices. In this study, we examine the trapping effect and temperature-dependent behavior of the HD-MOSFET. Furthermore, our analysis compares the effects of temperature and interface traps on the threshold voltage (Vth), channel mobility (µch), and on-state resistance (RON) within a temperature range of 300 K to 500 K.
AI Assisted Electrochemical Experimentation
Authors: Okubo Keiichi , Ling Chen
Published: December 2024

The current work proposes that artificial intelligence could not only guide the design of experiments but also serves as an independent quality control element. We demonstrate the proposed strategy in one of the most prominent electrochemical technique, rotating disk electrode. The control of RDE quality has been a challenge in electrochemical research for decades. The absence of controlled RDE experiments has partially contributed to the discrepancy of electrochemical studies even for the same material. To solve this challenge, we show that a CNN-method evaluated the quality of as-prepared electrodes with an accuracy of 88%. The CNN-model thus provided a simple, easy-to-use and non-destructive way to achieve the high-quality of RDE experimentation. The implementation was estimated to improve the experimental efficiency by 60%
(Invited) Using X-Ray Microscopy Techniques to Advance Fuel Cell Catalyst Layers
Authors: Bazylak Aimy
Published: December 2024

Despite the tremendous progress that has been made in developing polymer electrolyte membrane (PEM) fuel cells, there are still key challenges in optimizing the catalyst coated membrane. The catalyst layer has long been the focus of driving down cost and striving for long lifetimes and better performance, and these challenges are only heightened when we consider the evolving application focus – from a past focus on automotives to now the inclusion of heavy-duty vehicles and aviation. In this talk, I will discuss our approach to informing next generation catalyst coated membrane development. I will discuss how our work from the flow field and gas diffusion layer have informed our approach to the catalyst coated membrane. I will then focus on X-ray techniques that provide high spatial and temporal resolution for examining experimental performance and materials characterization, and I will discuss numerical modelling approaches, such as our work to uncover the impact of compression. I will discuss the advancement we are making in characterizing the spatio-chemical speciation of custom catalyst layers. Specifically, we probe the carbon, fluorine, and oxygen spectral K-edges on commercial catalyst layers using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) in conjunction with scanning transmission X-ray microscopy (STXM) to provide a comprehensive two-dimensional map of the PEM fuel cell catalyst layer. I will discuss the structural characteristics of the CL, which will be highly valuable for informing the design of next generation PEM fuel cell catalyst layers.
Oxygen Reduction Reaction Activity of Pt on Various Carbon Supports in OH- conducting Ionic Liquids
Authors: Fukuoka Kosuke , Yanagishita Takashi , Munakata Hirokazu
Published: December 2024

The intermediate temperature operation above 100 °C is one of important targets of next generation fuel cell development from both points of view of the activity enhancement and carbon monoxide poisoning mitigation of catalysts. To tackle this challenge, we have synthesized and applied OH- conducting ionic liquids as new fuel cell electrolytes, in which the progress of oxygen reduction reaction (ORR) has been successfully confirmed at temperatures above 100 °C under non-humid conditions. However, there is a problem to be solved that the overpotential for ORR is high due to the strong adsorption of ionic species on Pt catalyst. In this study, the electronic state of Pt catalyst was designed by applying heterogeneous atom-doped graphene materials as catalyst supports to reduce the ORR overpotential.

A 1:1 mixture of tetrabutylphosphonium hydroxide (TBPOH) and tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide (P4441TFSI) was prepared and used as OH- conducting ionic liquid. As Pt catalyst supports, reduced graphene oxide (RGO) and nitrogen-doped graphene (NG) were synthesized. The deposition of Pt catalyst on these graphene materials were carried out by a conventional reduction method of platinum chloride with ethylene glycol.

The ORR activity of Pt catalysts supported on various carbon materials was evaluated by cyclic voltammetry in O2 saturated TBPOH/ P4441TFSI at 120 °C, and the positive shift of ORR onset potential from 0.4 V to 0.6 V and then 0.7 V vs. RHE was observed by changing the support from commercial Ketjen Black to RGO and then NG, accompanied by an increase in the ORR current density. X-ray photoelectron spectroscopy (XPS) revealed that this improvement is related to the different electronic state of Pt catalyst, and it was suggested that the supports with higher electron donating properties such as NG are suitable for Pt catalyst to enhance the ORR activity.

Figure 1
Porous Nitrogen-Doped Carbon Supported Pt Nanocatalyst for Efficient Oxygen Reduction Reactions
Authors: WANG Zixin , Li Kui , Wang Xiaojing , Spendelow Jacob S.
Published: December 2024

Oxygen reduction reaction (ORR) at catalyst surface is the key kinetic limiting step in fuel cells that influence the overall cell performance in the energy conversion process. Rational design of the carbon supports with unique morphology and controllable porosity is challenging and significant for efficient and durable oxygen reduction electrocatalysis. Nitrogen-doped carbon nanospheres with uniform size and precise control over mesopores and micropores have been derived from mussel-inspired biomimetic polydopamine through a facile colloidal synthesis method and subsequent high-temperature pyrolysis. The unique surface structure of this nitrogen-doped carbon also dictated the morphologies of the deposited platinum nanoparticles, alleviating the particle dissolution, detachment, and agglomeration issue, which are main factors for catalyst degradation in working conditions. The ORR activity and durability of this electrocatalysts were studied in both rotational disk electrode (RDE) system and membrane electrode assembly (MEA), and a detailed structure-property relationship between porosity of carbon supports, Pt morphologies and fuel cell ORR performance was uncovered. This work is informative to researchers working in electrochemical materials field for developing efficient and robust electrocatalyst supports.

Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.
Preparation and Characterization of Platinum-Cobalt Nanosheets for Oxygen Reduction Reaction
Authors: Metawea Osama , Sugimoto Wataru
Published: December 2024

Enhancing the efficiency of Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is crucial for the broader use of polymer electrolyte fuel cells. Pt-based electrocatalysts are commonly used at the cathode side of polymer electrolyte fuel cells to facilitate the ORR, which is the most sluggish process during cell operation. Pt nanosheet prepared via topotactic reduction of platinum oxide nanosheets showed large electrochemically active surface area (ECSA)and high mass specific activity (MA).1 The addition of cobalt into the Pt nanosheet is expected to enhance and improve overall electrocatalytic performance as PtCo alloy nanoparticles are known to have higher specific activity than pure Pt. In this study, we present the synthesis and characterization of cobalt-doped platinum-oxide nanosheets ((Pt,Co)Ox NS) and their transformation into carbon-supported Pt-Co nanosheets for potential electrochemical applications.

The (Pt,Co)Ox NS colloid was obtained through exfoliation in aqueous solution by modification of our previous synthesis process.1 The results demonstrated enhanced electrocatalytic activity of the (Pt,Co)Ox NS composite compared to pure platinum-oxide nanosheets. For the pure platinum-oxide nanosheets, the ECSA was 97 m2 (g-Pt)-1. Moreover, employing the Koutecky-Levich equation, the MA was determined to be 321 A g-1 at 0.9 V vs. RHE, and the specific activity was 332 µA cm-2. For the PtCo nanosheets, the ECSA was similar at 91 m2 (g-Pt)-1. However, owing to the Co electronic effect, the specific activity rose to 576 µA cm-2, leading to an overall increase in MA to 524 A g-1 at 0.9 V vs. RHE. This improvement is attributed to the synergistic effect between cobalt and platinum, which enhances the oxygen reduction process.

Reference:

D. Takimoto, S. Toma, Y. Suda, T. Shirokura, Y. Tokura, K. Fukuda, M. Matsumoto, H. Imai, and W. Sugimoto, Nat Commun
14, 19 (2023)
(Invited) Non-PGM Catalysts for Electrochemical Energy Storage and Conversion
Authors: Kumar Kavita , Ku Yu-Ping , Pedersen Angus , Titirici Magda , Stephens Ifan , Bonnefont Antoine , Cherevko Serhiy , Dubau Laetitia , Jaouen Frederic , Maillard Frederic
Published: December 2024

Energy storage and conversion occur through the manipulation of molecular bonds, catalyzed at electrified interfaces between an ion conductor and an electrocatalyst material within electrochemical reactors like hydrogen fuel cells or water electrolysers. Nanostructured electrode materials are essential for minimizing energy losses and maximizing atom efficiency in these reactions. They provide significant advantages in atomic dispersion, leading to enhanced energy efficiency and performance benefits.

The rapid and efficient development of new nanostructured catalysts requires in-depth knowledge of the relationships between nanostructure and their electrocatalytic performance and stability. Such relationships appear of utmost importance for the scientific community.

In this presentation, I will highlight some structure-activity-stability relationships of non-platinum group metal (PGM) nanostructured catalysts in acid and alkaline media. Examples will be devoted to elucidating the degradation mechanisms of iron-nitrogen-carbon (Fe-N-C) materials during fuel cell operation. Various conditions were investigated, including potential range, gas atmosphere, electrolyte, and temperature [1]. Several ex situ and in situ physicochemical techniques were combined to differentiate possible degradation mechanisms. Specifically, the combination of inductively coupled plasma mass spectrometry measurements with a gas diffusion electrode and microkinetic models showed a positive correlation between the metal dissolution profile and the local pH variation in the catalyst layer of Fe-N-C [2].

Acknowledgments

These studies were financed by the French National Research Agency in the frame of ANIMA (grant number n°ANR-19-CE05-0039) project and the DEEP (grant number n°ANR-21-CE05-0021) project.

References

[1] a) K. Kumar, P. Gairola, M. Lions, N. Ranjbar-Sahraie, M. Mermoux, L. Dubau, A. Zitolo, F. Jaouen, F. Maillard, ACS Catal.
2018, 8, 11264-11276; b) K. Kumar, L. Dubau, M. Mermoux, J. Li, A. Zitolo, J. Nelayah, F. Jaouen, F. Maillard, Angew. Chem.
2020, 132, 3261-3269.

[2] Pedersen A, Kumar K, Ku Y-P, Martin V, Dubau L, Teixeira Santos K, et al. ChemRxiv. 2024; doi:10.26434/chemrxiv-2024-7p3cm.
Low-Electronegativity Mn-Contraction of Ptmn Nanodendrites Boosts Oxygen Reduction Durability
Authors: Nie Yan , Zhao Chuan
Published: December 2024

Platinum metal (PtM, M=Ni, Fe, Co) alloys catalysts show high oxygen reduction reaction (ORR) activity due to their well-known strain and ligand effects. However, these PtM alloys usually suffer from a deficient ORR durability in acidic environment as the alloyed metal is prone to be dissolved due to its high electronegativity. Herein, we report a new class of PtMn alloy nanodendrite catalyst with low-electronegativity Mn-contraction for boosting the oxygen reduction durability of fuel cells. The moderate strain in PtMn, induced by Mn contraction, yields optimal oxygen reduction activity at 0.53 A mg−1 at 0.9 V versus reversible hydrogen electrode (RHE). Most importantly, we show that relative to well-known high-electronegativity Ni-based Pt alloy counterpart, the PtMn nanodendrite catalyst experiences less transition metals' dissolution in acidic solution and achieves an outstanding mass activity retention of 96 % after 10,000 degradation cycles. Density functional theory calculation reveals that PtMn alloys are thermodynamically more stable than PtNi alloys in terms of formation enthalpy and cohesive energy. The PtMn nanodendrite-based membrane electrode assembly delivers an outstanding peak power density of 1.36 W cm−2 at a low Pt loading and high-performance retention over 50 h operations at 0.6 V in H2-O2 hydrogen fuel cells.

Figure 1
Durability and Structural Transformation of Pt Alloy Nanowires and Nanoparticles for the Oxygen Reduction Reaction in Acidic Media
Authors: Kato Masaru , Zhuang Yu , Kato Yuta , Iguchi Yoshimi , Li Tianchi , Tanioku Shinji , Yagi Ichizo
Published: December 2024

The oxygen reduction reaction (ORR) is catalyzed at the cathode in polymer electrolyte fuel cells (PEFCs). Since the ORR is sluggish and the electrocatalytic activity of the ORR catalyst determines the overall performance of PEFCs, highly active and durable ORR electrocatalysts have been intensively studied. The combination of alloying and nanostructuring of Pt is one of the promising approaches to develop such ORR electrocatalysts. Among the Pt-based shape-controlled electrocatalysts, Pt or Pt–M alloy nanowires (M = Ni and Co) are known to exhibit high ORR activity in the half cell [1,2]. Since nanowires have larger contact areas and therefore potentially higher adhesion to the carbon support than conventional nanoparticles, Pt-based nanowires should have higher durability. However, details of the effect of durability testing (potential cycles) on the structure of nanowires remain unclear.

In this work, we report synthesis of PtNi alloy nanowires at different temperatures under different atmospheres, and their structural transformation after potential cycles. PtNi nanowires were prepared at 433 K under Ar and air [3]. The difference in atmosphere affects the presence or absence of PtNi nanoparticles with PtNi nanowires: both PtNi nanowires and nanoparticles are produced under the inert condition of Ar, whereas PtNi nanowires are exclusively produced under the oxidative condition of air. PtNi nanowires with and without PtNi nanoparticles were converted into branched nanostructures after durability tests. PtNi nanowires were also prepared at different temperatures of 433, 493 and 553 K under Ar [4]. The Ni content in the PtNi nanowires increases from <5 at.% up to about 15 at.% with increasing synthesis temperature. The number of PtNi nanoparticles also decreases with increasing synthesis temperature. The PtNi nanowires in the co-presence of PtNi nanoparticles prepared at 493 K gave highly durable beads-on-nanowires with the Pt skin via Ostwald ripening of coexisting PtNi nanoparticles. This structural transformation is coupled with changes in the surface electronic structure, confirmed by in situ X-ray absorption spectroscopy. Understanding such a structural transformation will help us to design and develop highly durable Pt alloy nanostructured electrocatalysts for the ORR.

References.

[1] M. Li et al., Science, 354, 1414 (2016).

[2] Z. Zhao et al., Adv. Mater.,31, 1808115 (2019).

[3] M. Kato, Y. Iguchi, T. Li, Y. Kato, Y. Zhuang, K. Higashi, T. Uruga, T. Saida, K. Miyabayashi, I. Yagi, ACS Catal., 12, 259 (2022).

[4] Y. Zhuang, Y. Iguchi, T. Li, Y. Kato, M. Kato, Y. A. Hutapea, A. Hayashi, T. Watanabe, I. Yagi, ACS Catal., 14, 1750 (2024).
S-Doped La0.8Sr0.2(CrMnFeCoNi)O3 High Entropy Perovskite As Efficient Bifunctional Oxygen Evolution Reaction/Oxygen Reduction Reaction Electrocatalyst
Authors: Nguyen Thi Xuyen , Sun Jun-Hong , Ting Jyh-Ming
Published: December 2024

Developing non-noble metal, low cost, highly efficient and stable bifunctional oxygen evolution reaction (OER)/oxygen reduction reaction (ORR) electrocatalyst has attracted significant interests for several applications such as metal air battery. Herein, we report an S-doped high entropy perovskite oxide (HEPO) of La0.8Sr0.2(CrMnFeCoNi)O3 electrocatalyst for bifunctional OER/ORR electrocatalyst. We show that S-doped La0.8Sr0.2(CrMnFeCoNi)O3 electrocatalyst exhibits a low OER overpotential of 385 mV at 10 mA cm-2 and a half-wave potential of 0.728 V for ORR in 0.1 M KOH. The electrocatalyst also demonstrates excellent stability. Various in-situ analyses were performed to investigate the morphological and structural change of electrocatalyst during the OER and ORR processes. This study opens a new opportunity for further exploring advanced bifunctional electrocatalyst.