bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Polymer Controlled Synthesis of Metal-Carbon Nanostructures for Energy and Sensing Applications
Authors: Kisailus David
Published: December 2024

There is an alarming increase of pollutants being discharged into the atmosphere and water. This is predominantly due to the increased use of fossil fuels as well as the rapid emergence of technological developments within industries (e.g., pharmaceuticals). Nanostructures consisting of metal oxides offer potential solutions to many of these problems. However, their poor electrical and ionic conductivity still greatly hinder their practical implementation into energy storage and conversion (e.g., fuel cells, Li-ion batteries) or water purification applications. Carbon-based or modified nanomaterials have proven to enhance the performance and reduce the cost of many of these applications. Here, we have developed a general approach for the production of one-dimensional (1D) conductive and porous graphitic carbon fibers embedded with metal/metal oxide nanostructures. We interpret the mechanisms of nanoparticle and graphitic formation using a combination of microscopy and spectroscopy in order to exert control over the resulting nanostructures. By modifying synthesis conditions, we have produced self-supporting porous, high surface area carbon nanofiber-metal/metal oxide nanoparticle based membranes with controlled crystallite size, phase, and porosity. In addition, we describe recent developments in sensing, energy and water purification-based performance of these and other metal oxide/nitride based nanostructures.
Large Tunability of 2D Density in Atomically-Thin in2O3 By Mild Fluorine-Based Plasma
Authors: Chang Yu-Cheng , Lien Der-Hsien , Chen Chien-Wei
Published: December 2024

ALD-based atomically-thin In2O3 has gained a lot of attention due to its high mobility, wafer-scale growth and low temperature deposition compatible with back-end-of-line process. However, the excessively high carrier concentration of In2O3 limits its applicability in future electronic device. To address this problem, fluorine-based plasma treatment, which has been successfully used to modulate the carrier concentration in various material systems such as 2D and CNT, was performed on 4 nm ALD-based In2O3 transistor (as shown in Figure 1a). Importantly, the plasma is remote type and the treatment is performed at low temperature to avoid damage to the atomically-thin In2O3 transistor. After fluorine-based plasma treatment, the 2D density (n2D) of 4 nm In2O3 transistor significantly decreases from 2.8 × 1013 cm-2 to 4.1 ×1010 cm-2 corresponding to a ΔV
T equals to 70 V (as shown in Figure 1b). It was demonstrated that the n2D can be precisely reduced by controlling the treatment time and plasma power. The XPS analysis indicates that the reduction of n2D of In2O3 is due to the passivation of oxygen vacancies by fluorine atom and the capture of electrons by absorbed fluorine atoms, which possess a higher electronegativity than oxygen. Owing to the precise tunability of threshold voltage (V
T), we successfully realized the depletion-load NMOS inverter. This result indicates that fluorine-based plasma treatment and ALD-based atomically-thin In2O3 has significant potential for the future BEOL electronic applications.

Figure 1. a) Schematic representation of the structure of a In2O3 bottom-gate transistor and the fluorine-based plasma treatment process. b) The transfer characteristics of In2O3 transistors before and after fluorine-based plasma treatment.

Figure 1
(Invited) Progress in Fast 4H-SiC Crystal Growth and Defect Reduction By High-Temperature Gas-Source Method
Authors: Tsuchida Hidekazu , Kanda Takahiro
Published: December 2024

Practical applications of 4H-SiC Schottky barrier diodes (SBDs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) have started in various fields. Ongoing efforts to improve the productivity and quality of 4H-SiC wafers are crucial to further expand the production volume of the SiC power devices. The sublimation method is a standard growth process to produce SiC bulk crystals. In the method, powder source is sublimated at a temperature of ~2200ºC and recrystallized on a seed crystal. Although the growth techniques to obtain large diameter (150-200 mm) SiC substrates have developed using the sublimation method, the growth rates remain in about 0.3-0.5 mm/h. We have attempted to realize much higher growth rates in SiC crystal growth by the high-temperature gas-source method (high-temperature chemical vapor deposition) using SiH4 and C3H8 as the source gases and obtained ~3 mm/h or more at a high growth temperature at 2500-2550ºC and high input partial pressure of the source gases (>10 kPa for SiH4) [1]. Another topic in the high-temperature gas-source method can be realizing dislocation densities lower than those of the seed crystals. In the proper conditions, we observe no significant increase in the dislocation densities in the early stage of the growth and gradual reduction of the dislocation densities along the growth direction. In this paper, we introduce the key techniques in obtaining a high growth rate and high material quality in SiC bulk crystal growth by the high-temperature gas-source method.

[1] H. Tsuchida and T. Kanda, Materials Science in Semiconductor Processing 176 (2024) 108315.
Computer Aided Optimization of Insulated Gate Bipolar Transistors
Authors: Brungi Pranathi , Andrei Petru
Published: December 2024

Compared to other types of transistors, insulating gate bipolar transistors (IGBTs) have high on-state current and breakdown voltage, which make them ideal for low-frequency (<20 kHz) power applications, such as switching devices for motor drive systems and uninterruptible power supplies. Although the on-state voltage (VON) of IGBTs is smaller than the on-state voltage of metal-oxide-semiconductor field-effect-transistors at high current densities, VON remains relatively high at low-current densities, reducing the range of applications of IGBTs in the low-current regime. In this presentation, we discuss new results in the optimization of IGBTs using the adjoint method developed in [1]. First, we introduce the doping sensitivity functions of the on-state voltage, on-state resistance, and breakdown voltage and discuss the relationship between the three functionals. Then, we discuss and compare different ways of computing the doping sensitivity functions and present two applications: the first is related to the analysis of variability of on-state and breakdown voltage (from device to device), and the second is related to the global optimization of the doping profile of these transistors. Details about the numerical computation, numerical cost, and sample optimized structures will also be presented at the meeting.

References:

[1] C. Zhu, P. Andrei, “Adjoint method for the optimization of insulated gate bipolar transistors,” AIP Advances
9, 095301 (2019).
(Invited) metal Organic Framework Templates for the Fabrication of High Performance Photoanodes
Authors: Rosei Federico
Published: December 2024

The study of structure property/relationships in advanced materials is promising towards obtaining systems with desired functionalities. Such systems can then be used as building blocks for the fabrication of various emerging technologies. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation low cost manufacturing of devices. We focus in particular on recent developments in solar technologies that aim to address the energy challenge [1-5].

Here we present the use of Metal Organic Frameworks (MOFs) as templates for the fabrication of high performance photoanodes in next generation solar technologies. In particular, we describe the realization of NiO, mixed phase TiO2 and In2O3/CuO p-n heterojunction composite photoelectrodes, obtained using MOFs [6-8], for photoelectrochemical hydrogen generation from water.

[1] Nano Energy
79, 105416 (2021); [2] Chem. Eng. J.
446, 137312 (2022); [3] ACS Appl. Mater. Int.
15, 56413 (2023); [4] Small Meth.
8, 2300133 (2024); [5] J. Mater. Chem. A
11, 23821 (2023); [6] Appl. Cat. B
263, 118317 (2020); [7] Small
18, 2201815 (2022); [8] Small
19, 2300606 (2023).
(Invited) thermal Transport in Covalent Organic Frameworks
Authors: Giri Ashutosh
Published: December 2024

Covalent organic frameworks (COFs) are a rare class of organic materials whose solid-state structures can be designed at the level of their molecular components. Recent advancements in modern fabrication tools that provide atomic precision for their growth have shown that these materials possess great synthetic tunability, structural versatility, permanent porosities, large surface areas, and high chemical and thermal stabilities. As such, COFs are endowed with a wealth of unique physical properties, making them ideal candidates for flexible electronics, integrated circuits, gas separation and storage, catalysis, sensors and thermoelectrics. Although great progress has been achieved in their reticular chemistry, the fundamental understanding of thermal transport properties, underpinning the applicability of COFs in the aforementioned applications has been largely unexplored. However, these materials with extended and periodic structures, provide ideal platforms to test theoretical transport models and significantly advance our understanding of fthermal transport processes in condensed matter. Here, I will review our recent efforts into understanding their thermal transport properties through advanced atomistic simulations and state-of-the-art experimental tools. Our works highlight the immense potential to tune their thermal conductivities over a wide range, marking new regimes of materials design that combine superior thermal properties with low densities. Ultimately, the fundamental mechanistic understanding gained from our works will help guide the future syntheses of COFs for targeted applications with "user-defined" thermal transport properties.
(Invited) bridging MOFs to Applications Via Machine Learning
Authors: Moosavi Mohamad
Published: December 2024

MOFs (metal-organic frameworks) are materials with the potential to significantly improve several energy-related applications by allowing customization of their properties. However, traditional scientific methods make the process of discovery of scalable materials that perform well in industrial processes slow and complicated. This is due to the need for a holistic approach that considers the entire design process, including exploring vast materials spaces, linking them to their properties, synthesis, and process design and engineering. To tackle this challenge, we are developing tools using machine learning and artificial intelligence to help navigate the vast design space, uncover hidden relationships between material properties and performance, and accelerate MOF design.

In this discussion, I'll elaborate on how these novel tools are being used to quantify the structural diversity of large MOF material databases, develop physics-constrained machine learning methods for low-data design tasks, learn from failures to design better experiments and perform the inverse design of MOFs.
Surface Attachment of Metal-Organic Frameworks to Create Photo Responsive Porous Materials for Photocatalysis
Authors: Kissel Daniel
Published: December 2024

This work explores different techniques for anchoring Metal-Organic Frameworks (MOFs) to surfaces to develop photo responsive porous materials that can be used in photocatalysis. Surface attachment of MOFs were achieved using a variety of different techniques including electrochemical growth, covalent linkage, and electrophoretic deposition. The Zr(IV) and Ti(IV)-based MOFs UiO-66-NH
2 and MIL-125-NH
2 were anchored onto tetraethyl orthosilicate (TEOS) wafers via covalent attachment using polyaniline (PANI) crosslinking. This resulted in multi-layered, photo responsive glass electrodes that were investigated for photocatalysis. MIL-125-NH2 was also anchored onto the surface of a PANI-functionalized silica wafer using electrophoretic deposition. Electrochemical growth of Cu(II)-based MOFs onto graphite and titanium were also explored using 1,3,5-trimesic acid (BTC) and 1,4-terephthalic acid (BDC) to generate Cu-BTC and Cu-BDC frameworks on the surface. The properties of these electrochemically grown films were relatively easy to manipulate, allowing great control of their composition, thickness, and crystal size. Each functionalized material was characterized using Infrared spectroscopy, powder X-ray diffraction, and SEM imaging with EDS analysis. The photo responsive and photocatalytic properties were explored using different photo and electrochemical techniques including linear sweep voltammetry, cyclic voltammetry, and photovoltage response under simulated sunlight.
(Invited) application of Organic Frameworks for the Control of Electrochemical Processes and Electrocatalytic Properties
Authors: Park Jung Hyun , Yu Siying , Lee Chi Ho , Kwon Joseph Sang-Il , Yang Hong
Published: December 2024

Electrochemical processes including electrocatalysis often take place in aqueous electrolyte solutions. Their performances are influenced greatly by the structure of electrolyte-electrocatalyst interface, which may regulate mass transfer that is important in controlling surface reactions through altering the overall reaction kinetics. We recently designed and synthesized amine-based covalent organic frameworks (COFs) from triformylphloroglucinol and 2-nitro-p-phenylenediamine precursors through Schiff base reaction. In this presentation, I will present our recent results on the effects of these COFs on proton transfer at electrocatalyst-organic frameworks/electrolyte interfaces and their impacts on the electrocatalytic activity. In the experimental design, these organic frameworks were functionalized with amine (NH2), nitro (NO2) sulfonic (SO3) and other functional groups. We found these COFs exhibited excellent stability across a wide potential window under acidic conditions. We observed the use of functionalized amine-based COFs can act as a good modifier to facilitate proton transfer for hydrogen evolution reaction (HER). Results from the electrochemical solid-liquid interface (ESLI)-based density functional theory (DFT) calculations suggest that functionalized COFs increase the local hydrogen concentration at the COF-electrocatalyst interface. Our simulation data also suggests the enhancement in HER activity is achieved partially through the protonation of amine of the COFs, suggesting a new mode of interfacial control for enhancing the electrocatalytic kinetics.
Electrochromism Based on Reflective Color of Conductive Polymers
Authors: Yamada Katsumi
Published: December 2024

Some solid films of organic dyes, such as methylene blue, show a metallic luster. We are interested in the electrochromism of metallic luster and its reflected color from non-metallic materials. It has already been reported that 3-methoxythiophene polymers obtained by chemical and electrochemical synthesis show metallic luster. It was believed that this electrochemical polymerization could only produce a polymer product with high reflectance by slowly sweeping the applied potential, but a metallic luster was achieved by using a different electrolytic polymerization procedure. A constant potential is applied at which the monomer polymerizes, followed by a constant potential at which the polymer product obtained on the electrode is reduced. A polymer film that showed a green metallic luster in a reduced state and a red metallic luster in an oxidized state was obtained by repeating these potentiostatic electropolymerization procedures. We call this method as multi-step potentiostatic polymerization. These color tones were obtained when no light was transmitted through the polymer film, and we believe that they are caused by reflection on the surface of the polymer film. For reference, when white light was transmitted through the polymer film obtained, red color was observed in the reduced state and blue color was observed in the oxidized state. This is electrochromism based on transmitted color, which is well known as polythiophene electrochromism. By performing electrochromism with metallic luster, it becomes possible to apply it to switchable Mirror mirrors.
Leveraging Functional High-Entropy Oxide Perovskites for Enhanced Piezocatalytic Degradation
Authors: Liu Heng-Jui , Ye Yi-Chen , Tsai Yun-Wei
Published: December 2024

The escalating prevalence of water scarcity resulting from extreme climate events highlights a critical global challenge. This scarcity emphasizes the need for wastewater recycling, emphasizing the pivotal role of the water cycle in sustaining life and ecosystems. Among various wastewater treatment processes, chemical methods stand out for their high pollutant removal efficiency, scalability, and versatility in addressing diverse wastewater types. Advanced Oxidation Processes (AOPs) are particularly favored due to their low energy consumption, minimal equipment requirements, and superior remediation efficiency. Catalyst-triggered AOPs, particularly piezocatalytic processes, have recently emerged as highly promising systems, utilizing functional materials like ferroelectrics or piezoelectrics to degrade toxic organic pollutants with the assistance of sonication.

This presentation unveils a potential piezocatalyst system based on the concept of high entropy materials, demonstrating a rapid dye removal strategy. Specifically, we explore a lead-based high entropy perovskite, Pb(Mg,Nb,Zr,Ti,Hf)O3 (PMNZTH), through two synthesis methods to study its dye removal efficiency and corresponding mechanism. Hydrothermal-synthesized PMNZTH exhibits significant dark adsorption and piezocatalytic dye degradation effects simultaneously, achieving approximately 90% dye removal efficiency within 60 minutes. Results suggest that K2O compounds from the synthesis environment enhance PMNZTH's dark adsorption capability by increasing specific surface area and surface potential. This research underscores the potential of high entropy perovskites as efficient adsorbents and catalysts for wastewater treatment.

In the second part, focusing solely on the piezocatalysis effect on dye degradation, we adopt PMNZTH synthesized through the solid-state method. This approach offers a straightforward method to elucidate the proper mechanism behind two controversial models for piezocatalysis — the screening charge effects and energy band theory — by investigating key parameters such as piezoelectric coefficient and band gap. Results indicate a positive correlation between dye removal efficiency and the piezoelectric coefficient, but an inverse relationship with the band gap as the Ti/Hf element ratio varies, suggesting the dominance of screening charge effects in piezocatalysis. Our work provides insights into piezocatalysis mechanisms and proposes a rational design concept using high entropy materials as potential piezocatalysts for water purification.
Piezo-Photocatalytic Water Splitting of MoS2@Mo2CTx Heterostructure Catalyst
Authors: Lin Hsun-Yen , Wu Jyh-Ming
Published: December 2024

A heterostructure comprised of two-dimensional transition metal dichalcogenides (2D-TMDs) and transition metal carbide/nitride (MXenes) was fabricated. The substrate for the growth of 2D MoS2 nanoflowers (NFs) was established using the highly conductive metal phase Mo2CTx MXene. The resulting MoS2@Mo2CTx catalysts exhibited a remarkably enhanced piezocatalytic hydrogen (H2) generation rate, reaching 1164.8 μmol･g-1 h-1, being 4.01 times and 3.06 times higher than the individual pristine Mo2CTx and MoS2 counterparts, respectively. Moreover, with the introduction of light irradiation, the piezo-photocatalytic H2 yield rate of MoS2@Mo2CTx reached 2191.1 μmol･g-1 h-1, showing a 1.88-fold increase compared to the piezocatalytic yield rate. The hetero-catalyst demonstrated commendable reusability and long-term stability, yielding an impressive 9039.1 μmol･g-1 of hydrogen gas under simultaneous ultrasonic vibration and light irradiation within an 8-hour timeframe. Finite element method (FEM) simulations were also employed to validate the piezo-voltage output of the ultrasonic-force-triggered hydrogen evolution reaction (HER) systems.

Figure 1
Light-Driven Organic Transformation with Bismuth Vanadate Photoanodes
Authors: Kuang Chun-Chung Brian , Chen Yi-Wen , Fong Jun-Lin , Tu Guan-Zhu , Jiang Chang-Ming
Published: December 2024

Photoelectrocatalysis stands at the forefront of transformative advancements in the chemical industry, offering a path toward a more sustainable future. Harnessing abundant solar energy through semiconducting photoelectrodes, this approach drives redox reactions directly at the electrolyte interfaces, significantly reducing the required energy input and eliminating the need for toxic or costly homogeneous catalysts. Beyond water splitting and carbon dioxide reduction, the applicabilities of photoelectrocatalysis have been expanded to biomass upgrading and synthetic chemistry over the last ten years. In this work, we focus on the selective conversion of benzyl alcohol to benzaldehyde in acetonitrile, excluding the formation of benzoic acid, employing indirect photoelectrocatalysis with bismuth vanadate (BiVO4) as a photoanode, achieving nearly 100% Faradaic efficiency. Notably, our investigation reveals the emergence of surface states formed between BiVO4 and the redox mediator, N-hydroxy-succinimide (NHS), resulting in a gradual decline in photocurrent density over time. Small perturbation techniques, including electrochemical impedance spectroscopy and intensity-modulated photocurrent spectroscopy, were utilized for probing into the carrier dynamics at the electrolyte interface. In addition to blocking charge transfer sites of BiVO4, adsorption of NHS radicals also facilitates charge recombination on the photoelectrode surface. In addressing this issue, we present evidence that the density of these surface states can be effectively suppressed through optimized photoelectrode deposition methods as well as dopant incorporation. The roles of electrolytes and trace water impurities were also systematically analyzed. Our findings underscore the critical importance of understanding the chemical and dynamic landscapes at the semiconductor-electrolyte junction for unlocking the full potential of photoelectrocatalysis. This work sheds light on the intricacies of the photoelectrocatalytic processes and offers valuable insights for advancing the field and directing energy flow toward target molecular transformations with unique product selectivity.
Dual Side Passivation Strategy with Multifunctional Organic Molecules for High Performance Wide Bandgap Perovskite Solar Cells
Authors: Yu Subin , Ko Min Jae
Published: December 2024

Perovskite-based tandem solar cells have received great attention, however, the wide bandgap (WBG) perovskite solar cell (PSC) used as the top layer still faces issues to overcome, including large open-circuit voltage (V
OC) loss and halide segregation. Over the years, small organic molecules have been introduced at the interfaces between perovskite and charge transport layers to mitigate V
OC losses, by passivating interfacial defects. Herein, we propose novel multifunctional organic molecules, i.e., octylammonium (OA) and N-methylsulfanilic acid (NMSA), at the top and bottom sides of perovskite light absorbing layer. We investigated the distinct roles of OA and NMSA components and examined the effects of passivation depending on the position of interfacial treatment such as bottom, top and dual sides of perovskite. It is observed that V
OC deficits decreased from 0.58 V to 0.44 V, leading to the increase of the power conversion efficiency (PCE) from 16.24% to 19.83% for the 1.77 eV WBG PSCs. Furthermore, we demonstrate that halide segregation is significantly suppressed. The optimized WBG PSC maintained 98.9% of its initial PCE after 3300 seconds under 1-sun illumination, demonstrating enhanced maximum power point tracking stability. This study contributes to the development of next-generation high-performance PSCs, providing a deeper understanding of interfacial defect engineering.
Exploring the Stability of Azto Tfts: The Critical Role of Oxygen Partial Pressure in Performance Optimization
Authors: Kim Sang Ji , Kim Hyeondong , Lee Sang Yeol
Published: December 2024

Amorphous oxide semiconductors, such as indium-gallium-zinc oxide (IGZO), have attracted significant attention due to their high electron mobility and low processing temperatures compared to amorphous silicon (a-Si). These characteristics make IGZO suitable for large-area applications, and its transparency holds promise for next-generation electronic devices. However, the commercialization and large-scale production of IGZO are limited by the toxicity of indium and the high cost of gallium. In this context, AZTO can emerges as a cost-effective and less toxic alternative. This study explores the fabrication and characterization of bottom-gate thin-film transistors (TFTs) using aluminum-zinc-tin oxide (AZTO) as an alternative channel material. AZTO films were deposited at room temperature via radio frequency (RF) magnetron sputtering with varying ratios of oxygen and argon. Comprehensive measurements, including temperature stress (TS), negative bias temperature stress (NBTS), activation energy, and density of states (DOS), were conducted to evaluate the electrical properties and stability of the TFTs. The results indicate that increasing the oxygen partial pressure during deposition reduces oxygen vacancies, significantly enhancing the stability of the devices. These findings highlight AZTO as a cost-effective and less toxic alternative to IGZO, particularly in display applications. Additionally, the study provides insights into the fundamental mechanisms governing the electrical behavior of AZTO-based TFTs, further confirming their suitability for advanced display technologies.
Synthesis of Co@N-C Porous Electrocatalysts in Alkaline Electrolytes and Their ORR Applications
Authors: Kim Hee Soo , Lee Hae In , Lim Dong-Ha , Cho Jaehoon
Published: December 2024

In recent years, petrochemical-based energy sources have been used for decades, and many researchers have been trying to switch from petrochemical energy sources to clean energy sources to solve the problem of global warming. Among the various green energy sources, fuel cells that use hydrogen and oxygen as raw materials to generate energy from water and electricity have recently gained attention. However, problems such as platinum's small reserves and poor durability have been a major obstacle to the widespread use of fuel cells. In order to solve these problems, we synthesized catalysts in the form of carbon composites doped with inexpensive transition metals and nitrogen with excellent electrical conductivity and evaluated their performance as ORR catalysts in alkaline electrolytes. Depending on the optimal heat treatment synthesis conditions and the ratio of Co and dopamine precursor, we found the best synthesis method in alkaline conditions of 0.1 M KOH, which shows excellent ORR performance due to the synergistic effect of nitrogen-doped carbon and Co. Although the performance is still inferior to that of commercial platinum catalysts, further improvements are expected to improve the performance to that of platinum catalysts.

Figure 1
Catalytic Activities of Pt-Y-Ni/C Synthesized Using Microwave-Polyol Process for Oxygen Reduction Reaction in PEMFC
Authors: Kim Tae-Won , Jeong Seo-Jin , Lee Hyeon Bin
Published: December 2024

Developing highly active and durable catalysts for sluggish cathodic oxygen reduction reaction (ORR) has been a core issue for the broad commercialization of proton exchange membrane fuel cells (PEMFCs) Despite Pt/C being used as a typical ORR catalyst in commercial PEMFC stacks, lots of efforts are being made to overcome the high loading and poor durability of Pt/C [1]. Recently, the notable results of Pt-based binary alloys with rare-earth metals or transition metals have been reported to demonstrate promising catalytic performance as an ORR catalyst [3, 4]. Nevertheless, further optimization for higher activity and durability of ORR catalysts under harsh operating conditions is strongly required from the viewpoint of the industrialization of PEMFCs.

In this study, we report highly active and durable Pt-based ternary electrocatalysts, PtYNi/C, synthesized using a simple microwave-polyol process. The Pt-based ternary electrocatalysts were uniformly dispersed on the surface of the V-72R carbon support, with mean particle sizes ranging from 3.4 to 4.2 nm, depending on the composition ratio of Pt, Y, and Ni. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements using a rotating disk electrode (RDE) revealed that the specific activity of the PtYNi/C catalysts decreased from 602 mA/cm² to 332 mA/cm², and the mass activity decreased from 390 mA/mgPt to 264 mA/mgPt at 0.9ViR-free, as the Pt content decreased from 90 at% to 65 at% in the PtYNi/C catalysts. Nevertheless, these values are superior to those of the TKK Pt/C catalysts used as a reference. We have demonstrated that the reduction of Pt loading by alloying with abundant elements can be achieved using microwave-polyol synthesis, thereby enhancing the activity of the catalyst. In the presentation, we will discuss the detailed structural, compositional, and chemical characterization results for PtYNi/C synthesized using microwave-polyol synthesis, including their catalytic activity loss after 30k ADT cycles.

References

K. Debe, Nature, 2012, 486,43–51.

Cui, R., Mei, L., Han, G. et al. Scientific Reports., 2017, volume 7, 41826

Shaik Gouse Peera, et al. Sustainable Energy Fuels, 2019,3, 1866-1891
Carbon-Embedded Pt Alloy Cluster Catalyst: Properties and Oxygen Reduction Activity
Authors: Shin Sang yong , Lee Hyunjoo
Published: December 2024

Carbon-embedded PtFe alloy cluster catalysts have emerged as promising candidates for enhancing the performance and durability of oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). These catalysts, synthesized through a multi-step process involving carbonization of hyper-crosslinked polystyrene particles with Fe precursors, doping of nitrogen species, deposition of Pt precursors, and subsequent reduction, exhibit remarkable properties and catalytic activity.

Advanced imaging techniques, including aberration-corrected scanning transmission electron microscopy (ADF-STEM) and scanning electron microscopy (SEM), have revealed that the metal clusters are embedded beneath the carbon support surface. X-ray absorption fine structure (XAFS) analysis further confirmed the Pt-Fe alloy structure of the metal clusters, which are approximately 1.5 nm in size. The carbon-embedded PtFe alloy cluster catalysts demonstrate high mass activity and exceptional durability for the ORR. Despite being embedded within the carbon matrix, the Pt sites within the clusters serve as active sites for electrochemical reactions. Co-adsorption of Br- ions with protons alters cyclic voltammetry (CV) curves similarly to typical Pt/C catalysts, indicating the accessibility of Pt sites. Moreover, small molecules such as protons formic acid, and methanol can effectively diffuse through the carbon layer to reach the Pt surface.

When applied in the cathode of PEMFCs with a low Pt loading of 0.05 mg Pt cm-2, the PtFe cluster catalysts exhibit high current density at 0.65 V and excellent durability. After 30,000 cycles, the current density remains nearly unchanged, highlighting the superior performance of these catalysts compared to conventional Pt/C or PtFe/C catalysts. Density functional theory (DFT) calculations further elucidate the catalytic mechanism of the carbon-embedded PtFe alloy clusters. Carbon atoms stably adsorb on Fe sites of PtFe clusters, making nearby Pt sites active for ORR with optimal adsorption strength of oxygen intermediates. This comprehensive understanding of the catalytic behavior and properties of carbon-embedded PtFe alloy cluster catalysts opens up new avenues for the development of highly active and durable ORR catalysts in PEMFCs, with minimized Pt usage.

Figure 1
Investigation of High Entropy Alloy Nanoparticles Assisted By Resonance Acoustic Mixing for Oxygen Reduction Reaction
Authors: Hyun Jinho , Pak Chanho
Published: December 2024

High-entropy alloy (HEA) nanoparticles (NPs) are highly promising for electrocatalysis because of their wide range of compositions, adaptable active sites, and robust stability. Nevertheless, synthesizing these complex compositions as uniform NPs remains a challenge by conventional synthesis methods due to variations in reduction rates among metal precursors, leading to phase separation. This study presented a straightforward and scalable method for producing HEAs using a liquid-assisted (LA) solid-state reduction followed by an annealing process. Employing a resonance acoustic mixer (RAM), this process provides a rapid and scalable means for producing dispersed HEA NPs on carbon support. Quinary HEA (PtNiCuCoZn) catalysts were synthesized by initial mixing and reduction using RAM and further annealing under nitrogen at 900 ℃, sequentially. The resulting HEA electrocatalysts have a narrow particle size distribution with minimal particle agglomeration and demonstrate enhanced mass activity (0.75 A/mgPt) and stability toward oxygen reduction reaction (ΔE1/2=16 mV after 10k cycles), outperforming conventional Pt/C catalysts (~0.2 A/mgPt) while achieving superior Pt utilization.
Synthesis and Characterization of Titanium Nitride-Supported Iridium-Nickel Alloys as Highly Active Electrocatalysts for Hydrogen Evolution Reaction
Authors: Pham Toan Minh , Yim Kyungmin , Kim Jinsoo
Published: December 2024

Iridium serves as the active electrocatalyst in driving the hydrogen evolution reaction (HER), an important process in water-splitting technology for the production of green hydrogen. However, the expensive cost and limited durability of Ir-based catalysts have hindered the widespread application of HER. Thus, there is research interest in reducing the mass loading of Ir and enhancing long-term stability. In this work, we synthesized highly stable titanium nitride (TiN) to serve as the supporting material for low-loading Ir-Ni alloys (Ir-Ni/TiN) utilized in HER. The TiN was derived from the pyrolysis of titania nanotubes (TNT) with melamine, resulting in a higher surface area than commercial TiN. Additionally, varying percentages of Ni were employed to investigate the influence of alloy composition on Ir catalytic activity. Electrochemical tests conducted in both 0.5 M H2SO4 and 1.0 M KOH media demonstrated that Ir-Ni/TiN exhibited enhanced activity, with ultra-small overpotentials (η10) of 8 mV and 22 mV, respectively. Furthermore, the utilization of TiN substantially was illustrated to increase the long-term stability of the catalyst compared to carbon-support materials. Therefore, this study provides an effective strategy for improving the performance of Ir-based electrocatalysts in HER.
Unitized Regenerative Fuel Cells Employing Dendritic Pt and Ir Nanoparticles Supported By an Electrochemically Stable Oxide
Authors: Oh Hyung-Suk
Published: December 2024

Unitized regenerative fuel cells (URFCs) offer a cost-effective solution for energy conversion by functioning as both fuel cells and electrolyzers. Anion-exchange membrane-based URFCs (AEM-URFCs) require bifunctional electrocatalysts, such as Pt–Ir alloys, for the oxygen evolution reaction (water electrolysis mode) and oxygen reduction reaction (fuel cell mode). However, the low stability of Pt in alkaline media and high cost of Ir remain challenges for the widespread application of these URFCs. In this study, a Pt–Ni octahedral alloy is synthesized to replace Ir with Ni as the oxygen evolution reaction catalyst. The alloying effect of Pt–Ni inhibited the dissolution of Pt and transformed PtO
x
to metallic Pt via a recovery process, thereby providing a new operational strategy for improving the durability of AEM-URFCs. Remarkably, the performance of the AEM-URFC single cell is maintained over 10 cycles after the recovery process, demonstrating the viability of this approach for long-term operations. These findings will pave the way for broader applications and advancements of AEM-URFCs.

Figure 1
Enhancement of Alkaline OER Performance of the Electroplated Ni-P Catalysts Using Electrochemical Dealloying Technique
Authors: Oh Hyunjun , Eom Kwang Sup
Published: December 2024

With the growing attention on renewable energy, hydrogen is receiving attention as an energy carrier to resolve the temporal and spatial constraints of renewable energy. Electrical energy generated from renewable energy can be efficiently stored and transported in the form of hydrogen. Here, water electrolysis consists of two reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the high activation energy of OER is the main bottleneck of water electrolysis. Consequently, highly active catalysts are indispensable. Currently, the Pt- and Ir-based noble metal catalysts boast the highest performance for OER, but face significant commercialization hurdles due to their high cost.

Transition metal-based compounds are promising as substitutes of Platinum group materials for OER catalysts due to their high catalytic activity and earth-abundant properties. In particular, transition metal phosphides (TMPs) such as Ni-P are receiving much attention due to its remarkable catalytic performance approaching that of Pt-based one. In Ni-P, electrons are transferred from Ni to P due to the difference in electronegativity, allowing the energy of the HER and OER intermediate to be controlled for optimal activity. Furthermore, the Ni-P synthesized through electrodeposition has high potential as a promising substitute because they can have a variety of P ratios on the N-P surface, that can significantly affect catalytic activity and improve it more. Unfortunately, however, the electrodeposited Ni-P mostly has a flat and aggregated morphology, resulting in a low surface area and hence low catalytic performance. Therefore, to maximize the catalytic performance of the electroplated Ni-P. it is necessary to increase in surface area and number of active sites as well as the optimization of surficial P ratio.

In this context, we propose a morphology control method using electrochemical dealloying, which can greatly increase the surface area of the electroplated Ni-P. Specifically, under acidic conditions, a potential higher than the reduction potential of Ni causes partial dealloying of Ni on the Ni-P catalyst. Then, the partial dealloyed Ni creates defects between grains and forms a porous structure. As a result, the surface of the dealloyed Ni-P catalyst was exposed along the grain boundaries through SEM, and a quantitative increase in surface area was confirmed through cyclic voltammetry (CV). In addition, it was confirmed through XPS analysis that the bond between Ni and P became stronger, and based on this, it was confirmed that the tafel slope and TOF of the catalyst increased. The increase in overall performance of the catalyst was confirmed through the polarization curve as surface area and intrinsic activity increased.

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Atomically Dispersed Electrocatalysts for Low Temperature Fuel Cells and Water Electrolysis
Authors: Lee Jinwoo
Published: December 2024

Single-atom catalysts (SACs) have attracted growing attention because the number of active sites, with unpredictable catalytic activity can be maximized. Despite numerous studies on SACs, there is little research on the support, which is essential to understanding SAC. In this presentation, we report on the influence of the support on the performance of the SAC by comparing with single-atom Pt supported on carbon (Pt SA/C) and Pt nanoparticles supported on WO3-x (Pt NP/WO3-x). The results revealed that the support effect was maximized for atomically dispersed Pt supported on WO3-x (Pt SA/WO3-x). The Pt SA/WO3-x exhibited a higher degree of hydrogen spillover from Pt atoms to WO3-x at the interface, compared with Pt NP/WO3-x, which drastically enhanced Pt mass activity for hydrogen evolution (up to 10 times). This strategy provides a new framework for enhancing catalytic activity for HER, by reducing noble metal usage in the field of SACs. We have designed an oxophilic support material, WC1-x, for SAC to enhance the HOR activity of Ru SAC in alkaline condition by lowering the PZC of the electrode sufficiently to adsorb negatively charged OH- even in the HOR potential region.
Highly Active Raney-Nickel Electrodes Based on 3D Pin Structures for Use in High Temperature Alkaline Electrolysis
Authors: Albers Justin , Lau Marius , Bernaecker Christian Immanuel , Ashaju Abimbola , Harbiye Ahmad , Weissgaerber Thomas , Key Adam
Published: December 2024

The efficiency of alkaline electrolysers can be improved in a multitude of ways from overall system design to optimal operation conditions. One possibility is to increase the operating temperature which usually is 80 °C for industrial electrolysers. Increasing the temperature is a straightforward way to increase system efficiency significantly but leads to escalating corrosion problems due to the high concentration of KOH and the presence of oxygen (dissolved and gas phase) in the anolyte.

In this work we have developed highly active electrodes for the use at 120 °C. The electrodes are based on engineered 3D pin structures that were coated with Raney-Nickel. Since the interplay between electrode structure and catalyst layer are crucial for electrode performance in alkaline electrolysis a selection of nickel pin structures based on nickel mesh with differences in pillar as well as hole shape and size were investigated to find a optimal configuration. The aluminum for the formation of leachable NiAl-phases was applied by rolling Aluminum foil of varying thickness onto the pin structures. A following heat treatment and leaching resulted in a layer of Raney-Nickel on the substrates. The general performance at standard operating conditions was investigated as well as the behavior at 120 °C in 40 wt% KOH. The obtained electrodes showed excellent performance at a current density of 500 mA/cm² with overvoltages below 110 mV as cathodes and below 300 mV as anodes. During these tests and an additional testing campaign, the corrosion resistance of the Ni substrate and specially developed alloys under anodic conditions were evaluated.

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The Potential of Ruthenate Pyrochlores As Anodic Electroctalysts for PEM Water Electrolysisoral Presentation
Authors: Heath Megan Muriel , Fosdal Closs Elise , Sunde Svein , Reksten Anita Hamar , Sunde Tor Olav , Müller Magdalena , Røe Hågen , Rajbhandari Abhishek , Seland Frode
Published: December 2024

Green hydrogen is becoming a hot commodity in the light of escalating oil and gas prices and their uncertain future availability. Among various electrolysis technologies, PEM water electrolysis (WE) is favorable for its portability, modularity, and the ability to integrate with intermittent, renewable energy sources. However, the upscaling of PEMWE is not feasible yet due to the need for rare and expensive metals as electrocatalysts. Specifically, iridium oxide is used as state-of-the art anodic electrocatalyst. Ruthenium oxide also has an excellent activity towards the anodic oxygen evolution reaction (OER), but is highly unstable. To address this limitation, this study investigates ruthenate pyrochlores as alternative anodic electrocatalysts. The pyrochlore structure may stabilize ruthenium. The pyrochlores in this study have been synthesized using a traditional citrate sol-gel method,1 as well as a novel combustion synthesis route. Physical characterization of the electrocatalysts has been conducted using x-ray diffraction (XRD), scanning (transmission) electron spectroscopy (S(T)EM) and Raman spectroscopy. Additionally, ex-situ electrochemical characterization has been performed in a three-electrode setup. Linear-sweep voltammetry results of Y2Ru2O7 synthesised via the citrate sol-gel route indicate an overpotential of 300 mV at a current density of 10 mA cm-2. This result agrees well with what has previously been reported for this electrocatalyst.2 Y2Ru2O7 synthesised via the novel combustion route performs better than the aforementioned due to increased surface area. Various A-site dopants have also been introduced into the pyrochlore structure to generate oxygen vacancies, modify the electronic structure and increase the stability. These materials have also been tested in a full-cell setup to gauge their performance for practical applications compared to state-of-the-art IrO2 and RuO2.

References

(1) Kim, J.; Shih, P.-C.; Tsao, K.-C.; Pan, Y.-T.; Yin, X.; Sun, C.-J.; Yang, H. High-Performance Pyrochlore-Type Yttrium Ruthenate Electrocatalyst for Oxygen Evolution Reaction in Acidic Media. J. Am. Chem. Soc.
2017, 139 (34), 12076–12083.

(2) Feng, Q.; Zou, J.; Wang, Y.; Zhao, Z.; Williams, M. C.; Li, H.; Wang, H. Influence of Surface Oxygen Vacancies and Ruthenium Valence State on the Catalysis of Pyrochlore Oxides. ACS Appl. Mater. Interfaces
2020, 12 (4), 4520–4530.
Developing Catalysts for Proton and Anion Exchange Membrane Water Electrolyzers
Authors: Jeon Sun Seo , Lee Hyunjoo
Published: December 2024

To achieve carbon neutrality, extensive research is ongoing to produce green hydrogen via water electrolysis combined with renewable energy sources. Understanding and developing catalysts for membrane electrode assembly (MEA) type water electrolysis systems, such as proton exchange membrane water electrolysis (PEMWE) and anion exchange membrane water electrolysis (AEMWE), are critical steps toward this goal. Therefore, this presentation will focus on catalyst development for PEMWE and AEMWE, with emphasis on cost-effective catalysts.

For oxygen evolution reaction (OER) catalysis in PEMWE, the primary challenge is to minimize iridium (Ir) usage for sustainable green hydrogen production. Layered monoclinic iridium nickel oxide (IrNiOx) platelets were synthesized using a molten salt method and employed for the OER. These platelets exhibited high OER activity with reduced Ni dissolution in acidic conditions. When applied in MEA, they demonstrated enhanced interconnectivity within the catalyst layer, promoting electron transfer. Even at low Ir loading (0.2 mgIr cm-2), the platelets showed good performance with an initial cell voltage of 1.70 V at 1 A cm-2 and minimal degradation over 100 hours. This highlights the effectiveness of incorporating transition metals into Ir oxide to reduce Ir usage in PEMWE.

For oxygen evolution reaction (OER) catalysis in AEMWE, attention is focused on nickel iron (NiFe) hydroxide catalysts for their high activity and stability in alkaline conditions. However, the lack of initial electrical conductivity of as-prepared NiFe LDH limits its potential as an electrocatalyst. To address this issue, a monolayer structuring approach was proposed. This method improved mass transport to allow a high energy conversion efficiency of 72.6% with exceptional stability over 50 hours at 1 A cm-2. Additionally, lack of initial electrical conductivity hinders determination of electrochemically active surface area (ECSA) of NiFe LDH using conventional double layer capacitance method. Use of electrochemical impedance spectroscopy (EIS) at reactive OER potentials to extract the capacitance that is hypothesized to arise due to reactive OER intermediates (O*, OH*, OOH*) adsorbed on the catalyst surface was thus investigated. This allowed the estimation of ECSA and intrinsic activity of NiFe LDH, validating the methodology through rigorous catalyst loading and support studies.

For hydrogen evolution reaction (HER) catalysis in AEMWE, replacing platinum (Pt) with Ni-based alloys containing molybdenum (Mo) species has shown promise. Dynamic active sites of Ni catalysts with Mo species require innovative approaches to maintain initial performance, warranting material innovation or careful manipulation of operating protocol. The approaches in which this is made possible is shortly presented, together with the innovations that allows probing of such phenomenon.