Water electrolysis under microgravity

Matsushima, Hisayoshi; Nishida, Tetsuo; Konishi, Y.; Fukunaka, Yasuhiro; Ito, Yasuhiko; Kuribayashi, Kazuhiko

doi:10.1016/s0013-4686(03)00579-6

Cited by 122 publications

(59 citation statements)

References 16 publications

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“…17 This indicated that platinum became more hydrophilic under hydrogen, which inhibited the formation of the oxide surface layer. 22,23 Two aqueous solutions of 0.36 M KOH and 0.1 M H 2 SO 4 were chosen as a model electrolyte of alkaline and acid, respectively. An anodic potential was applied to the platinum electrode.…”

Section: Resultsmentioning

confidence: 99%

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Majima

Matsushima

Fukunaka

et al. 2014

J. Electrochem. Soc.

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The dynamic behavior of the meniscus of a potassium hydroxide and sulfuric acid droplet on a platinum electrode was studied using a charge-coupled device (CCD) camera and confocal laser microscopy. The three-phase interface was investigated during the hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER). Contact angle measurements revealed a spreading interface during the HER whereas the droplet shape remained unchanged during the HOR for both droplets. The overhead view revealed the formation of many fine droplets near the meniscus boundary during the HOR in the alkaline electrolyte, which agrees with previous results for the oxygen reduction reaction (ORR). The correlation of these observations with electrochemical data and differences in the results between the HOR and the HER suggest that the motion of the meniscus was induced by local pH and temperature gradients, presumably caused by a non-uniform reaction because of the limitations of the dissolved gas. Hydrogen is an attractive energy source as an alternative to fossil fuels. [1][2][3][4] Hydrogen can be produced from water and used in fuel cells. No toxic gases are generated and thus energy shortages and environmental problems can be prevented. Unitized regenerative fuel cells (URFCs) are ideal energy devices.5-7 They function by generating electricity as fuel cells and they produce hydrogen gas by water electrolysis. They are compact and economic because common electrodes may be used. However, URFCs require highly controlled wettability and this is dependent on the operational mode. A hydrophobic nature is desired for the fuel cell mode and a hydrophilic is required for water electrolysis. Therefore, intrinsic interfacial properties make it difficult to improve the energy conversion efficiency.The complex interface consists of an electrode (solid), an electrolyte (liquid), and a gas (air) and this is referred to as the three-phase interface, which is an essential part of the relevant electrochemical reaction. The meniscus plays an important role in controlling the reaction rate. [8][9][10][11][12][13] Inaba et al. reported that the hydrogen oxidation reaction (HOR) was affected by the shape of the meniscus, which determines the diffusion path of the dissolved gas.14 With an alkaline electrolyte, interesting interfacial phenomena have been observed. [15][16][17][18][19][20][21] In a previous study, we observed an in situ meniscus motion during the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) on a platinum electrode. 17 A spread of the three-phase interface during the ORR was observed and the role of hydroxide ions in determining the surface tension was investigated.To clarify the mechanism of this dynamic motion, in this study we measured the contact angle using different electrolytes and gas atmosphere used in a previous study. The relationship between the wettability and the electrochemical reaction of the HOR and the hydrogen evolution reaction (HER) is thus discussed in detail. ExperimentalThe experi...

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Section: Resultsmentioning

confidence: 99%

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Majima

Matsushima

Fukunaka

et al. 2014

J. Electrochem. Soc.

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“…Detachment of the bubbles also depends on the electrode wettability, i.e., on the electrolyte replacement at the electrode/electrolyte interface. 96,97 Appropriate coatings can be applied on the electrode surface to make it more hydrophilic, thereby reducing the surface coverage by gas bubbles. Another approach is based on the addition of surfactants to the electrolyte solution to reduce its surface tension and facilitate detachment of bubbles from the electrodes.…”

Section: Resistances In the Systemmentioning

confidence: 99%

“…The contributions of the electrode surface coverage by gas bubbles and the electrolyte--phase bubble void fraction to the Ohmic drop have been discussed. 97 Reducing the bubbles' residence time on the electrode surface is fundamental to minimize their size and thus reduce their resistance.…”

Section: Future Trendsmentioning

confidence: 99%

Hydrogen production by alkaline water electrolysis

Santos¹,

Sequeira²,

Figueiredo³

2013

Quím. Nova

370

226

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Recebido em 13/12/12; aceito em 28/5/13; publicado na web em 17/7/13Water electrolysis is one of the simplest methods used for hydrogen production. It has the advantage of being able to produce hydrogen using only renewable energy. To expand the use of water electrolysis, it is mandatory to reduce energy consumption, cost, and maintenance of current electrolyzers, and, on the other hand, to increase their efficiency, durability, and safety. In this study, modern technologies for hydrogen production by water electrolysis have been investigated. In this article, the electrochemical fundamentals of alkaline water electrolysis are explained and the main process constraints (e.g., electrical, reaction, and transport) are analyzed. The historical background of water electrolysis is described, different technologies are compared, and main research needs for the development of water electrolysis technologies are discussed.

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“…The topic of electrogenerated bubbles has been investigated by many researchers, for example [88][89][90][91][92][93][94]. The behavior of bubbles on gas-evolving electrodes is of great interest because it significantly affects the mass transport.…”

Section: Mgso 4 -Based Inchworm Resultsmentioning

confidence: 99%