Single bubble growth during water electrolysis under microgravity |
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Authors: | Hisayoshi Matsushima Daisuke Kiuchi Yasuhiro Fukunaka Kazuhiko Kuribayashi |
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Affiliation: | aInstitut fuer Experimentelle und Angewandte Physik, Christian Albrechts Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany;bGraduate School of Energy Science, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan;cInstitute of Space and Astronautical Science, Sagamihara 229-8510, Japan |
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Abstract: | Single bubble evolution on a micro-electrode (Pt, φ = 0.2 mm) was observed in 0.36 M KOH solution under terrestrial (1-G) and microgravity (μ-G) environments. The bubble size during galvanostatic electrolysis (j = −2.6 × 103 A m−2) was measured by CCD images, which allowed us to calculate the gas evolution efficiency, fG, by comparison with the consumed charge. The efficiency under μ-G increased until 1 s after starting electrolysis and then reached constant value (fG = 0.85), while, under 1-G, it showed a lower value and remarkably decreased 2 s after the beginning of the measurement. Such differences between μ-G and 1-G were explained by the mass transfer rate of the dissolved gas. Bubble-induced microconvection dominated the mass transfer under μ-G without any buoyancy force, on the other hand, the single-phase free convection (microscopic natural convection) influenced the bubble growth under 1-G. |
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Keywords: | Gas evolving electrode Micro-electrode Mass transfer Microgravity Supersaturation |
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