bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Formation of Porosity and Metallic Particles on 2D Oxides Via Photothermal Effect Toward High Performance Formaldehyde Sensing
Authors: Ryu Ahrom , Nahm Sahn , Jang Ji-Soo , Choi Ji-Won 
Published: December 2024

In recent years, the precise detection of Volatile Organic Compounds (VOCs) has become increasingly crucial owing to their substantial effects on both the environmental and human well-being. Within the spectrum of VOCs, formaldehyde (HCHO) stands out as a pollutant in indoor air and has been classified as a human carcinogen. Conventional gas sensor technologies have faced limitations in terms of their response speed, sensitivity, and ability to distinguish between difference gases. Consequently, the development of high-performance gas sensors with excellent selectivity, low operating temperature, fast response, and short recovery time has become imperative for effective detection and analysis of HCHO gas.
2D metal oxides have attracted significant attention across various scientific research fields due to their extraordinary physicochemical properties derived from unique crystal structures and surfaces. However, unfortunately, there are still challenges to achieving fast and sensitive chemical sensing using 2D metal oxides, primarily due to their limited surface porosity.
Here, a simple but powerful synthetic approach is proposed for producing highly porous and catalyst-loaded 2D metal oxides via a combination of 2D oxide exfoliation and flash-thermal shock (FTS). The molecular thin 2D Ti0.87O2 are simply synthesized by ion-exchange exfoliation and subsequent ultra-fast FTS (7.5 ms) process, resulting in simultaneous formation of uniform pores and catalytic Ti nanoparticles (NPs) on 2D Ti0.87O2 surface.
Ti nanoparticles (NPs) on surface of 2D Ti0.87O2. Density functional theory calculations and ex-situ TEM analysis reveal that the fast phase transformation of 2D Ti0.87O2 are key driving force of porosity and Ti NPs formation. Based on these features, the porous 2D Ti0.87O2 demonstrates an exceptional HCHO sensing performances, including outstanding reversibility and sensitivity even at room temperature.
Catalytic Combustion Type H2 Gas Sensor Based on Cerium Oxide
Authors: Tamura Shinji , Sakurai Asuki , Imanaka Nobuhito 
Published: December 2024

Hydrogen gas is the most promising clean energy source, but its use carries an explosion hazard (LEL: 4 vol%). Therefore, the real-time and accurate detection of H2 gas leakage at every emitting site is required with the compact sensor to prevent a critical accident. Among the compact H2 gas sensors proposed, the catalytic combustion type gas sensor using precious metal-loaded γ-Al2O3 such as Pt/Al2O3 as the catalyst is one of the sensors in practical use because of its long life and low-cost features. However, platinum is an expensive and scarce resource, and its use is desired to be reduced. Therefore, for the realization of the coming hydrogen society, the development of novel catalytic combustion type sensor using a noble-metal-free catalysts is important.
In this study, we focused on CeO2, Fe2O3, Co3O4, NiO as H2 oxidation catalyst and investigated the sensing performance of these metal oxides. In addition, we applied CeNbO4
+δ [1], having high oxide ion conductivity and redox property, as a promoter for CeO2 catalyst, and the H2 gas sensing performance of the sensor with 4 wt% CeO2/CeNbO4
+δcatalyst was investigated.
Among the sensors applied metal oxide (CeO2, Fe2O3, Co3O4, NiO), the sensor with CeO2 showed highest sensor output which is over 2 times higher than the sensors with other metal oxides. This is due to high specific surface area and low heat capacity of CeO2. Although the sensor using CeO2 showed good sensing performance, quantitative detection of H2 required a temperature of 105 °C or higher, which is still high for practical use.
To improve the H2 oxidation activity of CeO2, we applied CeNbO4
+δ as a promoter and the sensor with 4 wt% CeO2/CeNbO4
+δcatalyst. Figure 1(a) displays the response curves to H2 gas concentration change for the sensor applied 4 wt% CeO2/CeNbO4
+δ and CeO2. The sensor with 4 wt% CeO2/CeNbO4
+δcatalyst showed about 2.6 times higher sensor output compared to the sensor with only CeO2, indicating that the combination of CeNbO4
+δ improves H2 oxidation activity. Furthermore, the sensor with 4 wt% CeO2/CeNbO4
+δcatalyst was able to detect H2 gas concentration quantitatively even at 75 °C (Fig. 1(b)) with a 90% response time of about 14 seconds. The sensitivity to other gases such as carbon monoxide, methane, ethanol, and acetaldehyde was examined, and the sensor showed excellent selectivity for H2 at 75 °C.
[1] Y. Jin, Y. Quan, J. Liu, C. Qui, P. Pan, B. Shan, H. Luo, and P. Yang, J. Solid State Chem., 313, 123318 (2022).

Figure 1
Nanocellulose-Based Chiroptical Sensors for Detecting Circularly Polarized Light
Authors: Kang Saewon 
Published: December 2024

Natural materials exhibit fascinating optical properties that manipulate light across multiple length scales through hierarchical photonic structures, forming a promising platform for advanced optical materials. However, developing photonic structures that are both environmentally sustainable and capable of maintaining superior optical and structural properties for use in electronic devices remains a significant challenge.
In this work, we present chiroptical nanocellulose papers as flexible circularly polarized light (CPL) photodetectors. Optoelectrically activated 2D semiconducting channels are seamlessly integrated onto the nanocellulose papers, enabling high polarization-sensitive photoresponsivity that detects CPL handedness, facilitated by selective light propagation with substantial asymmetry. These flexible devices also demonstrate excellent mechanical durability while retaining their structural and chiroptical properties. We will discuss polarization-dependent optoelectronic behavior in the context of CPL sensing, with applications in next-generation bio-photonic devices.
Cathode Reaction Analysis of Lithium-Oxygen Battery Based on Operando XRD Measurements
Authors: Maeda Kazuno , Aoki Makoto , Dilixiati Dilinigeer , Kondo Toshihiro 
Published: December 2024

Introduction

The lithium-air battery (LAB), which has ten times the energy density of conventional lithium-ion batteries (LIB), is one of the promising candidates for the next-generation storage batteries, and there are great expectations for its development [1]. However, the reaction mechanism of the cathode reaction is still unclear, and the type of Li2O2 that is the product of the cathode in discharging is still unknown. The main reason for this is considered to be that it was difficult to directly observe the compounds generated at the cathode during LAB operation. By improving the laboratory XRD and the observation cell, we succeeded in operando XRD measurements of the cathode reaction in the LAB. In addition, under general conditions, the cathode product was Li1.5O2 with some Li missing from the crystal lattice of Li2O2 [2]. Here, we describe the details and discuss the reaction mechanism.

Experimental

An electrochemical cell covered with a Kapton® dome was constructed to allow constant oxygen flow to the cathode side of the LAB, and was attached to the diffractomator of a Rigaku Ultima IV XRD measurement system. A Cu Ka was used as the incident x-ray, a high-speed one-dimensional detector was used as the detector, a Ketjen black free-standing film was used as the cathode material, and tetraglyme solution with 0.5 M LiTFSI + 0.5 M LiNO3 + 0.2 M LiBr was used as the electrolyte solution. The LAB was discharged and charged at a constant current density of 0.4 mA/cm2 for 10 hours (4.0 mAh/cm2) each, and the XRD profile was recorded every 20 minutes. Each XRD profile was subjected to Rietveld analysis using Rigaku’s SmartLab Studio II software to determine the cathode product and its crystal structure.

Results and discussion

In the XRD profile measured during discharging, a lot of peaks due to the cell parts were observed. But, several peaks due to the cathode product were also observed. As a result of detailed Rietveld analysis of these peaks, the cathode product at the discharging capacity of 4.0 mAh/cm2 was not Li2O2 but Li1.5O2. Instead of the normal LiO2 with a rectangular crystal structure, LiO2 with a hexagonal crystal structure, which is the same as that of Li2O2, was observed immediately after the discharge. As the discharge progressed, Li was added to it, and the lattice constant gradually extended in the c-axis direction, forming Li1.5O2 at a discharge of 4.0 mAh/cm2. In the presentation, the charging process and the charge-discharge cycle characteristics would also be discussed.

References

[1] W. J. Kwak, et al., Chem. Rev.
120, 6626 (2020).
[2] M. Aoki and T. Kondo, et al., J. Phys. Chem. C
127, 15051 (2023).
High-Performance Solid-State Li Metal Batteries Based on a Solid Polymer Electrolyte
Authors: Wang Peng , Bucur Claudiu , Andrei Petru 
Published: December 2024

Over the past decades, lithium-ion batteries (LIBs) have garnered considerable attention, emerging as the foremost commercial battery technology. Widely employed in portable electronics, electric vehicles, and energy storage stations, LIBs face challenges including safety concerns and low energy densities, prompting extensive research into next-generation battery technologies. Solid-state batteries are recognized as one of the most promising alternatives to conventional LIBs. Polymer-based solid-state electrolytes have garnered extensive attention for their softness and flexibility, offering relief from interface issues between electrodes and separators in contrast to inorganic solid electrolytes. Nonetheless, their drawbacks, including limited Li+ conductivity or narrow electrochemical windows (< 4 V), constrain their potential applications.
This presentation introduces a novel solid-state electrolyte (SSE) derived from a new polymer developed by Piersica Inc. (www.piersica.com), tailored for use in all-solid-state lithium metal batteries. The SSE exhibits remarkable conductivity (0.2 mS/cm) at room temperature and exceptional oxidized stability (approximately 4.9 V). When integrated into a solid cathode and lithium metal anode configuration, without the addition of any liquid electrolyte, the resulting solid-state pouch cell (~40 mAh) demonstrates over 90% of theoretical capacity, superior rate performance, and long-term stability (85% retention after 200 cycles) at room temperature. The polymer from Piersica Inc. holds considerable promise for advancing the development and performance of solid-state batteries.
Nitrogen-Doped Mesoporous Carbons Fabricated from Self-Assembled Block Copolymers for Electrochemical Production of H2O2
Authors: Kong Youngwon , Miyamori Yuta , Hatakeyama-Sato Kan , Hayakawa Teruaki , Nabae Yuta 
Published: December 2024

Nitrogen-doped mesoporous carbons are attracting significant attention as next-generation electrocatalytic materials due to their high specific surface area, high electrical conductivity, and exceptional chemical stability. Especially, due to the facilitated mass transport of products, high selectivity for the two-electron oxygen reduction reaction is expected, making it applicable to the synthesis of hydrogen peroxide (H2O2).¹ In this study, we focused on the soft template method by utilizing the self-assembly of a block copolymer (BCP) through microphase separation.² In our laboratory, we have been working on the synthesis of poly(4-vinylpyridine)-b-poly(2,2,2-trifluoroethyl methacrylate) (P4VP-b-PTFEMA). The significant repulsive interaction between these two components allows extensive control of the domain size. Furthermore, poly(4-vinylpyridine) serves as both the nitrogen and carbon sources and is selectively crosslinked by resol, thus enabling a high carbonization yield to be obtained. We employed this BCP as a soft template and introduce resol as a cross-linker for fabricating nitrogen-doped mesoporous carbons. Here, we investigated in detail the effects of the composition of the block copolymer and the amount of the crosslinker on the morphology and nitrogen content of the mesoporous carbon.
P4VP-b-PTFEMA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A mixture of P4VP-b-PTFEMA and resol was dissolved in DMF at 5 wt%, and the solution was evaporated and dried under vacuum at 100 °C for 24 hours to prepare a composite film. Subsequently, the film was heated to 900 °C to fabricate nitrogen-doped mesoporous carbons.
Small-angle X-ray scattering (SAXS) analysis of the composite film revealed various microphase-separated structures depending on the BCP-to-resol ratio (Fig. 1 (a)). Furthermore, nitrogen-doped mesoporous carbons with pore diameters ranging from 6.2 nm to 24 nm were fabricated using various molecular weights of PTFEMA (Fig. 1 (b)). Additionally, in our presentation, we will discuss how the pore size affects the selectivity of the two-electron reaction and the catalytic efficiency in the oxygen reduction reaction.
[Reference]
(1) Park et al., ACS Catal. 2014, 4, 3749.
(2) Liu et al., Polym. Chem.
2014, 5, 6452.
[Acknowledgement]
This study was financially supported by JSPS-KAKENHI(21K04828).

Figure 1
Impedance Analysis on Ant-Nest Corrosion of Copper- Effect of Phosphorus Content in Copper on Corrosion Morphology-
Authors: Kashiwa Takumi , Watanabe Hikari , Shitanda Isao , Itagaki Masayuki , Ito Shinichi , Hosogi Tetsuro 
Published: December 2024

In recent years, leakage of refrigerant due to ant-nest corrosion has become a problem in copper piping used in heat exchangers of air-conditioning equipment.1) In our laboratory, we have succeeded in electrochemically reproducing ant-nest corrosion by galvanostatic polarization of phosphorus-deoxidized copper immersed in 600 ppm, formic acid solution of pH 5.5 at a current density of 0.3 mA/cm2..2) The pits of ants-nest corrosion have a fractal structure with a repetitive branching shape. Our laboratory reported that the number of branching in ant-nest corrosion can be determined by using a transmission line model (TLM) with blanched structure equivalent circuit from impedance spectra.3) Furthermore, the oxidation phosphorus dissolved from copper causes a decrease in pH at the bottom of the small pore, and the pH decrease accelerates the branching. In this experiment, galvanostatic polarization was applied to copper tubes with different phosphorus contents as working electrodes to reproduce ant-nest corrosion. Furthermore, the number of branching of ant-nest corrosion was determined by impedance analysis using TLM. Based on these results, the effect of phosphorus content on corrosion morphology was discussed.
Experimental conditions:
The electrolyte solution was a 600 ppm formic acid solution of pH 5.5. Copper tubes with various phosphorus contents (0.003, 0.004, 0.007, 0.015, 0.31 wt%) were used as working electrodes. The outside of the copper tube was used as the working electrode (test surface), and the rest of the test surface was covered with insulating tape to define the electrode area (electrode area: 7.85 cm2). In addition, the bottom hole of the copper tube was covered with a rubber stopper to prevent the solution from entering to inside of the copper tube. The test surface was polished with abrasive papers No. 800, 1200, and 2000, polished with diamond pastes of 6, 3, and 1 μm particles diameters, and then cleaned with methanol. Constant current polarization was performed for 72 h at a current density of 0.3 mA/cm2 using a platinum wire as a counter electrode, a saturated KCl silver/silver chloride electrode (SSE) as a reference electrode.

References

1) S. Ito, T. Hosogi, M. Watanabe, H. Tsueoka, M. Itagaki, Zairyo-to-Kankyo，67, 37-40 (2018).
2) M. Itagaki, A. Makita, H. Watanabe, I. Shitanda, T. Hosogi, S. Ito, Electrochim. Acta 479, 143873 (2024).
3) M. Itagaki, Y. Hatada, I. Shitanda, K. Watanabe, Electrochim. Acta 55, 6255–6262 (2010).
Preparation of Ordered Nanohole Arrays by Anodization of Textured Metal Substrates
Authors: Umeki Kota , Yanagishita Takashi 
Published: December 2024

The anodization of metals can form nanohole array structures composed of various metal oxides. The resulting anodic oxide film is expected to be used in various applications, such as catalysts, electrodes, and sensors, because of the material's properties and unique geometric structure. When applying nanohole arrays obtained by anodization of metal substrates to various functional devices, it is important to control geometrical structures such as pore size and pore depth, which affect device performance. We previously reported that forming a pattern of depressions on substrate surfaces prior to anodization allows the formation of ordered nanohole arrays by subsequent anodization [1–3]. In previous studies, the depression pattern was formed by dry etching with a mask, which made it impossible to increase the area of the pattern. In this study, we investigated the formation of depression patterns using a template process and the control of the starting point of pore generation by anodic oxidation to form large-area ordered nanohole arrays. Herein, we present the results of our study using Sn as the model material.
Anodized porous alumina, which can self-assemble large-area ordered structures, was used as a template to form ordered depression patterns on the Sn substrates. An ordered anodic porous alumina membrane, used as a template, was obtained by selectively dissolving the Al substrate from the anodized sample. The Sn thin film was formed on the back side of the obtained template by thermal evaporation and electrodeposition, and the alumina membrane was peeled off to obtain a Sn thin film with an ordered depression pattern on the surface. The resulting Sn thin film was anodized to generate holes from each depression, resulting in an ordered nanohole array.
SEM observations confirmed that the ordered pattern on the anodic porous alumina backside was successfully transferred to the Sn surface by this process. Anodization of the obtained Sn thin films induced pore generation from each depression, resulting in ordered nanohole arrays. This process is expected to produce large-area ordered nanohole arrays because the anodic porous alumina used as a template can be fabricated in large areas. The Sn oxide nanohole arrays obtained by this method are expected to have various applications.
References
[1] T. Yanagishita T. Masuda, T. Kondo, and H. Masuda, Electrochem. Commun., 123, 106916 (2021).
[2] T. Yanagishita, T. Masuda, and H. Masuda, RSC Adv., 12, 6848 (2022).
[3] T. Yanagishita, Y. Osada, T. Masuda, and H. Masuda, J. Electrochem. Soc., 169, 063502 (2022).
Reaction of Calcium Titanate with Al Metal in Molten CaCl2
Authors: Kaneda Hisayoshi , Takenaka Toshihide 
Published: December 2024

A new innovative production process of Ti production replacing the Kroll process is desired. The authors have been researching the production of Al-Ti alloy by Al reduction of TiO2 in molten CaCl2. It was shown in our previous study that Ti was reduced by the reaction of Al metal and CaTiO3 in molten CaCl2 at 1500°C, and that excess CaO addition was effective. However, the Ti content in the obtained Al-Ti alloy was still very small. In this study, the effect of Al-Ti alloy formation in molten CaCl2 containing Ca4Ti3O10 was investigated, and the appropriate condition for Al-Ti alloy formation was studied.
Calcium titanate: Ca4Ti3O10 was prepared by sintering a molded mixture of CaO and TiO2, and a small Al lump was used as reductant. The influence de-greasing of the Al lump by NaOH solution as pretreat was examined in this study. Molten CaCl2 containing Ca4Ti3O10 with the Al lump was kept for 1~1.5 hour at 1400°C~1450°C, and cooled down. The Al lump after the experiment was rinsed with pure water, and analyzed by XRD and SEM-EDX.
Figure 1 shows the dependence of Ti content in the Al lump on the immersion time. A small amount of Ti was detected in Al lump, and the Ti content varied with the immersion time. In the case that the Al lump without the pretreatment was used, the Ti content slightly increased with the immersion time, but the content was only 0.32 at% for 1.5 hour immersion at 1400°C. It was shown in our previous study that the Ti content was 0.06 at% in molten CaCl2 with CaTiO3, and that the content became 0.62 at% in the bath containing CaTiO3 with extra CaO where the molar ratio of CaO to TiO2 was 4:3. The result in this study is consistent with our previous study, which implies that the type of titanate ion in the bath strongly affects its chemical reduction by Al. The pretreatment of the Al lump strongly affected the Ti content; in the case that the Al lump with the pretreatment was used, the Ti content remarkably increased with the immersion time, and the content became 6.74 at% for 1.5 hour immersion. Since the Ti content did not reach a plateau even after 1.5 hour, a higher Ti content is expected by longer immersion. The Ti contents at 1400°C and 1450°C were almost the same, so the temperature dependence of this reaction seems not significant. Since the reaction seemed not to reach the equilibrium and the Ti content in Al was still insufficient, a further investigation should be necessary for the development of effective Ti production by this method. The researches on the influence of the titanate concentration and on the interface control other than de-greasing can lead more effective reaction.

Figure 1