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Featured researches published by Keisei So.


Journal of Materials Chemistry | 2016

Direct electron transfer-type dual gas diffusion H2/O2 biofuel cells

Keisei So; Yuki Kitazumi; Osamu Shirai; Koji Nishikawa; Yoshiki Higuchi; Kenji Kano

H2/O2 biofuel cells utilizing hydrogenases and multicopper oxidases as bioelectrocatalysts are clean, sustainable, and environmentally friendly power devices. In this study, we constructed a novel gas diffusion bioelectrode with a sheet of waterproof carbon cloth as the electrode base and optimized the hydrophilicity/hydrophobicity of the electrode for both high gas permeability and high direct electron transfer bioelectrocatalytic activity. The electrode exhibited a large current density of about 10 mA cm−2 in the steady-state for both H2 oxidation and O2 reduction. The biocathode and the bioanode were coupled to construct a gas diffusion H2/O2 biofuel cell. The dual gas diffusion system allowed the separate supply of gaseous substrates (H2 and O2) to the bioanode and biocathode, with consequent suppression of the oxidative inhibition of the hydrogenases. The cell exhibited a maximum power density of 8.4 mW cm−2 at a cell voltage of 0.7 V under quiescent conditions.


Bioelectrochemistry | 2018

Reactivation of standard [NiFe]-hydrogenase and bioelectrochemical catalysis of proton reduction and hydrogen oxidation in a mediated-electron-transfer system

Saeko Shiraiwa; Keisei So; Yu Sugimoto; Yuki Kitazumi; Osamu Shirai; Koji Nishikawa; Yoshiki Higuchi; Kenji Kano

Standard [NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F (DvMF-H2ase) catalyzes the uptake and production of hydrogen (H2) and is a promising biocatalyst for future energy devices. However, DvMF-H2ase experiences oxidative inactivation under oxidative stress to generate Ni-A and Ni-B states. It takes a long time to reactivate the Ni-A state by chemical reduction, whereas the Ni-B state is quickly reactivated under reducing conditions. Oxidative inhibition limits the application of DvMF-H2ase in practical devices. In this research, we constructed a mediated-electron-transfer system by co-immobilizing DvMF-H2ase and a viologen redox polymer (VP) on electrodes. The system can avoid oxidative inactivation into the Ni-B state at high electrode potentials and rapidly reactivate the Ni-A state by electrochemical reduction of VP. H2 oxidation and H+ reduction were realized by adjusting the pH from a thermodynamic viewpoint. Using carbon felt as a working-electrode material, high current densities-up to (200 ± 70) and -(100 ± 9) mA cm-3 for the H2-oxidation and H+-reduction reactions, respectively-were attained.


Physical Chemistry Chemical Physics | 2014

Improvement of a direct electron transfer-type fructose/dioxygen biofuel cell with a substrate-modified biocathode

Keisei So; Shota Kawai; Yasuyuki Hamano; Yuki Kitazumi; Osamu Shirai; Makoto Hibi; Jun Ogawa; Kenji Kano


Journal of Power Sources | 2016

Dual gas-diffusion membrane- and mediatorless dihydrogen/air-breathing biofuel cell operating at room temperature

Hong-qi Xia; Keisei So; Yuki Kitazumi; Osamu Shirai; Koji Nishikawa; Yoshiki Higuchi; Kenji Kano


Electrochimica Acta | 2016

Significance of the Length of Carbon Nanotubes on the Bioelectrocatalytic Activity of Bilirubin Oxidase for Dioxygen Reduction

Keisei So; Maki Onizuka; Takuji Komukai; Yuki Kitazumi; Osamu Shirai; Kenji Kano


Chemistry Letters | 2014

Gas-diffusion and Direct-electron-transfer-type Bioanode for Hydrogen Oxidation with Oxygen-tolerant [NiFe]-hydrogenase as an Electrocatalyst

Keisei So; Yuki Kitazumi; Osamu Shirai; Kouhei Kurita; Hirofumi Nishihara; Yoshiki Higuchi; Kenji Kano


Journal of Electroanalytical Chemistry | 2016

Analysis of factors governing direct electron transfer-type bioelectrocatalysis of bilirubin oxidase at modified electrodes

Keisei So; Yuki Kitazumi; Osamu Shirai; Kenji Kano


Bulletin of the Chemical Society of Japan | 2014

Kinetic Analysis of Inactivation and Enzyme Reaction of Oxygen-Tolerant [NiFe]-Hydrogenase at Direct Electron-Transfer Bioanode

Keisei So; Yuki Kitazumi; Osamu Shirai; Kouhei Kurita; Hirofumi Nishihara; Yoshiki Higuchi; Kenji Kano


Journal of Electroanalytical Chemistry | 2016

Bioelectrochemical analysis of thermodynamics of the catalytic cycle and kinetics of the oxidative inactivation of oxygen-tolerant [NiFe]-hydrogenase

Keisei So; Rui Hamamoto; Ryosuke Takeuchi; Yuki Kitazumi; Osamu Shirai; Ryohei Endo; Hirofumi Nishihara; Yoshiki Higuchi; Kenji Kano


Electrochemistry Communications | 2016

Binder/surfactant-free biocathode with bilirubin oxidase for gas-diffusion-type system

Keisei So; Maki Onizuka; Takuji Komukai; Yuki Kitazumi; Osamu Shirai; Kenji Kano

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