課題番号 ：S-20-SH-0008
利用形態 ：共同研究型支援
利用課題名（日本語） ：新規カーボン材料の開発
Program Title (English) ：Development of New Carbon Nanomaterials
利用者名（日本語） ：パンディター・ウッキカマパン1),ウィシュダー・サッタヤラット1), 藤重雅嗣/2),
　　　　　　　　　　　　　竹内健司/2),ウィナッダー・ウォンウィリヤパン1)
所属名（日本語） ：1) キングモンクット工科大学ラドクラバン, 2) 信州大学
Affiliation (English) ：1) King Mongkut’s Institute of Technology Ladkrabang, 2) Shinshu University

１．概要（Summary ）
In this study, activated carbons (ACs) were prepared via acidic dehydration of durian husk (DH) for supercapacitor application. The DH was dehydrated using sulfuric acid and subsequently activated by using sodium hydroxide as chemical reagent at 720 °C to obtain ACs (hereinafter referred to as DA). Surpassing the commercial ACs and the ACs derived from the conventional carbonization and activation (hereinafter referred to as CA), the DA exhibited superior properties in high surface area (2578 m2/g) and
total pore volume (1.27 cm3/g). The DA can act as a suitable material for supercapacitor electrode with the specific gravimetric and volumetric capacitances of 145 F/g and 70 F/cm3 in an organic electrolyte. The device also showed a promising performance with an energy density of 32 Wh/kg and a power density of 316 W/kg. These results demonstrate that the preparation of ACs via acidic dehydration of DH offers the advantages in terms of simplicity, low cost, and short-time processing to achieve heteroatom self-doped ACs with a high surface area for high-performance supercapacitors.
２．実験（Experimental）
Firstly, fresh DHs were blended after drying and then were sieved using a mesh size of 1 mm. 5 g of DH powder was mixed with 10 mL of 1 M H2SO4 solution and was stirred for 10 min at 80 °C. The obtained hydrochar was washed and dried, and subsequently activated by NaOH (hereinafter referred to as DA). For comparison, the ACs derived from DH was also prepared via a conventional pyrolysis carbonization and activation processes as described elsewhere. For comparison, the commercial AC (YP50) was also used for characterization. The elemental and chemical compositions were characterized using X-ray photoelectron spectroscopy (XPS, PHI Quantera II). Nitrogen adsorption–desorption isotherm measurements were performed using a gas adsorption analyzer (Micromeritics ASAP 2020).
３．結果と考察（Results and Discussion）
Fig. 1(a) shows nitrogen adsorption-desorption isotherms of the DA, CA and YP50. All samples showed the similar shape, i.e. with a steep curve at the low-pressure range, then parallel to the relative pressure axis at the high-pressure range. The adsorption and desorption branches followed nearly the same path with a relatively narrow hysteresis loop. Thus, all samples can be classified as Type I isotherms (refer to the IUPAC classification) with micropore characteristics [1]. The porosities of the DA, CA and YP50 are summarized in Table 1. A larger adsorption volume shown in Fig. 1(a) implies a large surface area. Among them, the DA shows the highest surface area of 2578 cm2/g.
Fig. 1(b) shows the pore size distribution of all samples obtained by the DFT method. The pore size distribution of all sample is slightly different. The pore distribution of the DA is in the range of 0.8–3.0 nm, while those of the CA and YP50 are in the ranges of 0.8–2.4 nm and 0.8–2.0 nm, respectively. The DA shows a board range of size distribution,while the CA shows a sharp peak at approximately 1 nm, resulting a relatively high average pore size of the DA (approximately 1.98 nm). These results show that the porosity of the sample depend on the preparation method. The total volume of all samples shows the same trend of the surface area with the following order: DA > CA > YP50. These results show that the dehydration route can offer the ACs with a high surface area comparable to a conventional carbonization method.
Fig. 2 shows a wide scan XPS spectra of all samples. The quantitative analysis of element composition is summarized as shown in Table 1. It was found that the DA and CA are basically composed of carbon, oxygen, nitrogen and sulfur, while there are only carbon and oxygen found in the YP50, resulting in the lowest and highest carbon content of the DA and YP50, respectively. These results imply that the dehydration of DH is a promising approach to obtain nitrogen and sulfur-co-self-doped ACs with a high surface area.
４．その他・特記事項（Others）
[1] M. Thommes, K. Kaneko, A. V. Neimark, J. P. Olivier, F. Rodriguez-Reinoso, J. Rouquerol and K. S. W. Sing, Pure Appl. Chem., 2015, 87, 9
５．論文・学会発表（Publication/Presentation）
(1) P. Ukkakimapan, V. Sattayarut, T. Wanchaem, V. Yordsri, M. Phonyiem, S. Ichikawa, M. Obata, M. Fujishige, K. Takeuchi, W. Wongwiriyapan, M. Endo, Preparation of activated carbon via acidic dehydration of durian husk for supercapacitor applications. Diamond and Related Materials, 107 (2020) 107906.
６．関連特許（Patent）
なし