Yuta Nakayasu 교수

Hard carbon (HC) is the most promising candidate for sodium-ion battery anode materials. Several material properties such as intensity ratio of the Raman spectrum, lateral size of HC crystallite (L_a ), and interlayer distance (d₀₀₂ ) have been discussed as factors affecting anode performance. However, these factors do not reflect the bulk property of the Na⁺ intercalation reaction directly, since Raman analysis has high surface sensitivity and L_a and d

Abstract In this study, the use of biorefined wood materials in the fabrication of organic redox supercapacitors is proposed. Oak‐derived hard carbon (HC) is revealed to have a nanographite domain structure, showing conductivity as high as that of artificial graphite. The CO 2 ‐activated hard carbon (A–HC) has a conductivity one order higher than that of commercial activated carbon, with a surface area of 1126 m 2 g −1 . The energy densities of supercapacitors composed of a tetrachlorohydroquino

In this study, we investigated the synthesis of wood-sawdust-derived high-crystalline graphite-like carbon. The sawdust was first impregnated with Fe and semi-carbonized by a hydrothermal treatment (HT) at 250°C, followed by the second carbonization under N2 atmosphere and acid washing. For an iron-to-sawdust weight ratio of 4:10, graphite-like carbon was synthesized at a very low temperature of 850°C. This carbon has an average interlayer distance and crystallite size (d002: 0.337 nm, La: 35.8

Molybdenum disulfide (MoS2), an attractive material for energy conversion devices, is known to exhibit varying properties depending on the number of layers and the phase structure. In this study, we developed a supercritical hydrothermal process that allows the controllable synthesis of MoS2 nanosheets with various structural and morphological characteristics. Detailed characterization of the synthesized materials confirmed that the number of layers in the MoS2 nanosheets could be controlled by

Owing to the increasing global demand for carbon resources, pressure on finite materials, including petroleum and inorganic resources, is expected to increase in the future. Efficient utilization of waste resources has become crucial for sustainable resource acquisition for creating the next generation of industries. Rice husks, which are abundant worldwide as agricultural waste, are a rich carbon source with a high silica content and have the potential to be an effective raw material for energy

This study presents a simple one-pot synthesis method to achieve few-layered and defective Mo(S,Se)₂ and (Mo,W)S₂ by using supercritical water with organic reducing agents from simple and less-toxic precursors. This synthesis process is expected to be suitable for preparing other various kinds of TMD solid solutions.

MoS2 structures with large surface areas and edges for use as electrocatalysts in the hydrogen evolution reaction (HER) are typically synthesized via solvothermal and hydrothermal methods. However, to utilize the fabricated particles as electrodes, they should be applied on substrates in the form of inks; this requires additional processing. Furthermore, if the electrode has a three-dimensional structure with more than two sides, applying the ink to the entire surface is difficult. Therefore, th

Herein, we report the impregnation of chloranil into activated carbon micropores using scCO₂. The sample prepared under 105 °C and 15 MPa showed a specific capacity of 81 mAh g_electrode^-1, except for the electric double layer capacity at 1 A g_{electrode-Polytetrafluoroethylene (PTFE)}^-1. Additionally, approximately 90% of the capacity was retained even at 4 A g_{electrode-PTFE}^-1.

Supercritical ethanol (scEtOH), with its high solubility and reducibility, can be used as a medium to fabricate chalcogenide semiconductors from stable solid chalcogen sources. We fabricated Cu2ZnSn(S,Se)4 films via chalcogenization of Cu–Zn–Sn oxide precursor films using scEtOH to dissolve SeO2 and elemental sulfur (S8). The S/Se molar ratio and the bandgap of Cu2ZnSn(S,Se)4 films were controlled by changing the input ratio of selenium source (SeO2) to sulfur source (S8). Analysis indicated tha

Highly catalytic cathodes for oxygen reduction reactions under neutral conditions allow major improvement in the power output of microbial fuel cells (MFCs). This work reports iron azaphthalocyanine impregnated into oxidized multi-walled carbon nanotubes to form a molecularly synthesized non-precious metal electrocatalyst. The synthesized catalyst was characterized using a rotating ring and disk electrode in a neutral medium (pH = 7.4) and exhibited a four-electron transfer pathway. When incorpo

Microbial fuel cells (MFCs) present a promising alternative to traditional activated sludge treatment for livestock wastewater, offering a carbon‐neutral, sustainable approach to wastewater management. Activated sludge treatment requires significant energy input for aeration and produces unpleasant odors. MFCs eliminate the need for energy‐intensive aeration, simultaneously generating energy during wastewater treatment. Platinum‐based electrodes commonly used in the cathode of MFCs pose a signif

Iron–nitrogen–carbon (Fe–N–C) catalysts with Fe–N 4 coordination are promising alternatives to platinum-based materials for the oxygen reduction reaction (ORR), yet their instability in acidic media limits practical applications. Herein, we report a sustainable Fe–N–C catalyst (RH-Fe-N) synthesized from rice husks and pyrite, serving as carbon and iron sources, respectively. This approach eliminates the need for complex precursors such as metal–organic frameworks, using a simple three-step carbo

Abstract Quinone‐based supercapacitors have been a growing research target as the next generation energy storage due to their high energy density and their environmental sustainability. However, the commercialization of these organic supercapacitors remains challenging due to complex fabrication processes and insufficient electrochemical performance. In this study, we introduce a novel fabrication method, direct powder adhesion (DPA), which simplifies electrode production while enhancing rate pe