研究者詳細 - 伊藤　皇聖

伊藤　皇聖（イトウ　コウセイ）

Ito, Kosei

写真a

所属（所属キャンパス）: 理工学部電気情報工学科（矢上）

職名: 助教（有期）

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Highly efficient hydrogen production and selective CO<inf>2</inf> reduction by the C<inf>3</inf>N<inf>5</inf> photocatalyst using only visible light

Ito K., Noda K.

Physical Chemistry Chemical Physics （Physical Chemistry Chemical Physics） 26 （ 1 ） 153 - 160 2023年11月

ISSN 14639076

　概要を見る

The production of energy sources by metal-free photocatalysts based on graphitic carbon nitride (g-C3N4) has garnered substantial attention. In this study, nitrogen-rich carbon nitride (C3N5) was successfully synthesized through the thermal polycondensation of 3-amino-1,2,4-triazole. The structural and physical characterization has suggested that a portion of the triazine rings, which constitute the structural framework of g-C3N4, may be substituted with five-membered rings in C3N5. Furthermore, the polymerization of C3N5 proceeded more extensively than that of g-C3N4 from melamine precursors. The increased nitrogen content in C3N5 resulted in a heightened number of π-electrons and a narrowed energy bandgap, with the potential of the valence band maximum being negatively shifted. Additionally, photocatalytic assessments encompassing nitro blue tetrazolium reduction, H2 production from triethanolamine aqueous solution, and CO2 reduction in the liquid phase were performed. All findings demonstrated that C3N5 exhibits significantly superior photocatalytic properties compared to g-C3N4. It is particularly noteworthy that C3N5 selectively generates methanol and H2 from oversaturated CO2 solutions under visible light irradiation, while g-C3N4 selectively generates formaldehyde. These outcomes strongly indicate that C3N5 serves as a metal-free, visible-light-responsive photocatalyst, capable of contributing to both the production of renewable energy sources and the reduction of greenhouse effect gases.
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Visible light-assisted hydrogen generation over platinum-loaded tungsten trioxide nanorods with the hexagonal and triclinic phases

Ito K., Uchida R., Noda K.

Journal of Photochemistry and Photobiology A: Chemistry （Journal of Photochemistry and Photobiology A: Chemistry） 443 2023年09月

ISSN 10106030

　概要を見る

Visible light-assisted hydrogen (H2) generation was attempted for tungsten trioxide (WO3) nanorods (NRs) loaded with platinum (Pt). WO3 NRs were synthesized with a simple hydrothermal method using sodium tungstate as a precursor and oxalic acid as a structure-directing reagent. A variety of structural analyses clarify that both the end parts of a single hexagonal WO3 NR are transformed into triclinic WO3 when oxalic acid is added during the NR synthesis. The WO3 NR synthesized without oxalic acid (WO3(0)) displayed site-selective photodeposition of Pt cocatalysts on the (1 0 0) plane, whereas the Pt photodeposition occurred preferentially at the end (triclinic) parts of the WO3 NR synthesized with 0.05 M of oxalic acid (WO3(0.05)). These site-selective Pt deposition allows us to consider an inversion of the redox reaction field in WO3(0) and WO3(0.05) sample. Pt-loaded WO3(0.05) showed better photocatalytic activity ascertained in both methylene blue decomposition and H2 generation from water and methanol mixture, which can be brought about by a direct Z-scheme formed at heterojunctions between hexagonal and triclinic WO3 in a single NR. Finally, photoassisted H2 generation from water including ammonia borane with Pt-loaded WO3(0.05) was demonstrated, where a H2 generation rate under visible light irradiation was about 2.7 times higher than that in the dark. This result suggests a new strategy of efficient H2 generation based on synergetic effects of the WO3 NR photocatalysis and the Pt catalysis.
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