Generation Mechanism of Hydrogen Gas from Hardened Cement Paste by γ-Irradiation

1994 ◽  
Vol 353 ◽  
Author(s):  
K. Noshita ◽  
T. Nishi ◽  
M. Matsuda
Keyword(s):  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Hardened Cement ◽  
Gas Generation ◽  
Γ Irradiation ◽  
Waste Forms ◽  
Two Factors ◽  
G Value ◽  
Hydrogen Radicals

AbstractHydrogen gas is generated from cementitious waste forms by radiolysis of water. In the case of low level radioactive waste, gas yields have been confirmed to be sufficiently low by irradiation experiments. However, studies have suggested that the hydrogen generation rate in cementitious waste forms is larger than the rate calculated from the g-value (H2 yields for 100eV absorbed). In this paper, the factors that increase the gas generation were investigated quantitatively. Two factors were identified, the effect of an organic diethylene glycol which reacts with hydrogen radicals to produce hydrogen, and the effect of electrons generated in the cementitious matrix which decompose water to hydrogen. The hydrogen generation rate was confirmed to drop less than the rate calculated from the g-value when these factors were eliminated.

scholarly journals Thickness-dependent photoelectrochemical properties of a semitransparent Co3O4 photocathode

2018 ◽  
Vol 9 ◽  
pp. 2432-2442 ◽  
Author(s):  
Malkeshkumar Patel ◽  
Joondong Kim
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Alkaline Electrolyte ◽  
Stoichiometric Ratio ◽  
Gas Generation ◽  
Pec Cells ◽  
Gas Generation Rate

Co3O4 has been widely studied as a catalyst when coupled with a photoactive material during hydrogen production using water splitting. Here, we demonstrate a photoactive spinel Co3O4 electrode grown by the Kirkendall diffusion thermal oxidation of Co nanoparticles. The thickness-dependent structural, physical, optical, and electrical properties of Co3O4 samples are comprehensively studied. Our analysis shows that two bandgaps of 1.5 eV and 2.1 eV coexist with p-type conductivity in porous and semitransparent Co3O4 samples, which exhibit light-induced photocurrent in photoelectrochemical cells (PEC) containing the alkaline electrolyte. The thickness-dependent properties of Co3O4 related to its use as a working electrode in PEC cells are extensively studied and show potential for the application in water oxidation and reduction processes. To demonstrate the stability, an alkaline cell was composed for the water splitting system by using two Co3O4 photoelectrodes. The oxygen gas generation rate was obtained to be 7.17 mL·h−1 cm−1. Meanwhile, hydrogen gas generation rate was almost twice of 14.35 mL·h−1·cm−1 indicating the stoichiometric ratio of 1:2. We propose that a semitransparent Co3O4 photoactive electrode is a prospective candidate for use in PEC cells via heterojunctions for hydrogen generation.

Radiolytic Hydrogen G Values for Waste Materials

2004 ◽  
Author(s):  
J. G. McFadden
Keyword(s):  
Decay Mode ◽  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Type Material ◽  
Waste Materials ◽  
Gas Generation ◽  
Radioactive Materials ◽  
Initial Concentration ◽  
Paper Citation ◽  
G Value

The radiolytic generation of hydrogen and other gases that support combustion are of particular concern for the transportation and handling of packages containing radioactive wastes and materials. An estimate of initial concentration of hydrogen and the rate of hydrogen generation through radiolysis within packages is therefore needed before shipping or storing radioactive materials. The most common method to estimate hydrogen gas generation is called the G value method. This paper documents a comprehensive database of hydrogen gas G values. The database is available electronically. It includes over 400 G values compiled from over 50 papers available in the open literature. The database includes: paper citation, author(s), author(s) affiliation, paper comments, material type, material sub-type, material comments, G value by decay mode, and G value comments.

Gold nanoparticle-catalysed photosensitized water reduction for hydrogen generation

2015 ◽  
Vol 3 (9) ◽  
pp. 5176-5182 ◽  
Author(s):  
Donghua Li ◽  
Jean-François Wehrung ◽  
Yue Zhao
Keyword(s):  
Gold Nanoparticles ◽  
Gold Nanoparticle ◽  
Hydrogen Generation ◽  
Hydrogen Gas ◽  
Gas Generation ◽  
Water Reduction ◽  
Component Systems

Gold nanoparticles (AuNPs) can catalyze photosensitized water reduction for hydrogen gas generation by using conventional three-component systems.

Improved Hydrogen Gas Generation Rate of n-GaN Photoelectrode with SiO[sub 2] Protection Layer on the Ohmic Contacts from the Electrolyte

2010 ◽  
Vol 157 (2) ◽  
pp. B266 ◽  
Author(s):  
Shu-Yen Liu ◽  
J. K. Sheu ◽  
Chun-Kai Tseng ◽  
Jhao-Cheng Ye ◽  
K. H. Chang ◽  
...  
Keyword(s):  
Ohmic Contacts ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Gas Generation ◽  
Protection Layer ◽  
Gas Generation Rate

Enhanced hydrogen gas generation rate by n-GaN photoelectrode with immersed finger-type indium tin oxide ohmic contacts

2011 ◽  
Author(s):  
Shu-Yen Liu ◽  
Jhao-Cheng Ye ◽  
Yu-Chuan Lin ◽  
Kuo-Hua Chang ◽  
Ming-Lun Lee ◽  
...  
Keyword(s):  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Ohmic Contacts ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Gas Generation ◽  
Gas Generation Rate

LiNO3 Addition to Cement Which Prevents Aluminum Corrosion

1997 ◽  
Vol 506 ◽  
Author(s):  
T. Matsuo ◽  
T. Izumida ◽  
M. Hironaga ◽  
Y. Horikawa ◽  
T. Shiomi
Keyword(s):  
Underground Water ◽  
Hydrogen Gas ◽  
Disposal Site ◽  
Chemical Analyses ◽  
Metallic Aluminum ◽  
Gas Generation ◽  
Water Penetration ◽  
Waste Forms ◽  
Aluminum Corrosion ◽  
Land Disposal

ABSTRACTLiNO3 addition to cement was examined to prevent hydrogen gas generation from metallic aluminum in dry active wastes during waste solidification and under circumstances of underground water penetration into the land disposal site. And its reaction mechanism was identified by some chemical analyses. The volume of the hydrogen gas generation with LiNO3 addition was 10% as much as that without LiNO3, by formation of the insoluble Li-Al preservation film on aluminum. After the land disposal of waste forms, LiNO3 would be expected to be effective to prevent aluminum corrosion as long as the cement forms keep their alkaline character, and when it became ineffective, the circumstances around the waste forms can be made less corrosive for aluminum. The aluminum corrosion at that time would be as much as 10% of that without LiNO3 addition.

Influence of Oxygen Concentration and Alkalinity on the Hydrogen Gas Generation by Corrosion of Carbon Steel

2000 ◽  
Vol 663 ◽  
Author(s):  
A. Fujiwara ◽  
I. Yasutomi ◽  
K. Fukudome ◽  
T. Tateishi ◽  
K. Fujiwara
Keyword(s):  
Carbon Steel ◽  
Oxygen Concentration ◽  
Test System ◽  
Hydrogen Gas ◽  
Localized Corrosion ◽  
Generation Rate ◽  
Passive State ◽  
Corrosion Mechanism ◽  
Gas Generation ◽  
Gas Generation Rate

ABSTRACTA repository for low and intermediate level radioactive wastes will contain a great deal of carbon steel as reinforcement materials and waste containers. These steel components are expected to generate hydrogen gas due to reductive corrosion of carbon steel under repository condition. In this study, we have investigated the influence of the environmental factors such as oxygen concentration and pH in the solution on the rate of the gas generation. This rate was measured with a gas flow type test system under the controlled oxygen concentration, which simulates the redox conditions from initial to final environment in a repository. In addition, the corrosion mechanism was examined through the electrochemical tests.As a result, it has been found that pH in the solution and the oxygen concentration considerably affected the generation rate of hydrogen gas in various way. As to the influence of pH of the solution, it has been found that the gas generation rate increased with the increase of pH between 11.8 and 14. Further, as to the influence of the oxygen concentration, when the oxygen concentration in the blowing nitrogen gas was 2 ppm or more, the gas generation rate increased with the oxygen concentration. This trend was possibly caused by local decrease of pH due to localized corrosion. The gas generation rate was very low when the oxygen concentration was in the passive region. The rate was equal to 0.01 μm/y or less if the corrosion occurs with an equation: 3Fe+4H2O → Fe3O4 + 4H2 ↑ to 0.01 *m imcro;/y (hereafter we call this the equivalent corrosion rate). However the gas generation rate increased when the oxygen concentration was controlled to the extent that sufficient passive film cannot be produced and thus it shifts from passive state to active state.

scholarly journals Solid-State NaBH4/Co Composite as Hydrogen Storage Material: Effect of the Pressing Pressure on Hydrogen Generation Rate

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1184 ◽  
Author(s):  
Olga Netskina ◽  
Elena Tayban ◽  
Anna Ozerova ◽  
Oxana Komova ◽  
Valentina Simagina
Keyword(s):  
Solid State ◽  
Sodium Borohydride ◽  
Cobalt Chloride ◽  
Hydrogen Generation ◽  
Generation Rate ◽  
Pressing Pressure ◽  
Gas Generation ◽  
Chloride Hexahydrate ◽  
Cobalt Chloride Hexahydrate ◽  
Gas Generation Rate

A solid-state NaBH4/Co composite has been employed as a hydrogen-generating material, as an alternative to sodium borohydride solutions, in the long storage of hydrogen. Hydrogen generation begins in the presence of cobalt-based catalysts, immediately after water is added to a NaBH4/Co composite, as a result of sodium borohydride hydrolysis. The hydrogen generation rate has been investigated as a function of the pressure used to press hydrogen-generating composites from a mechanical mixture of the hydride and cobalt chloride hexahydrate. The hydrogen generation rate was observed to increase with the increase of this pressure. Pre-reduction of the cobalt chloride, using a sodium borohydride solution, leveled this dependence with a two-fold decrease in the gas generation rate. According to TEM and XPS data, oxidation of the particles of the pre-reduced cobalt catalyst took place during preparation of the composites, and it is this oxidation that appears to be the main reason for its low activity in sodium borohydride hydrolysis.

Gas Generation Behavior of Transuranic Waste Under Disposal Conditions

1999 ◽  
Vol 556 ◽  
Author(s):  
Ryutaro Fujisawa ◽  
Tetsunari Kurashige ◽  
Yusuke Inagaki ◽  
Muneaki Senoo
Keyword(s):  
Stainless Steel ◽  
Carbon Steel ◽  
Initial Period ◽  
Hydrogen Gas ◽  
Generation Rate ◽  
Gas Generation ◽  
Geological Disposal ◽  
Synthetic Groundwater ◽  
Gas Generation Rate ◽  
Transuranic Waste

AbstractThe generation of hydrogen-gas from metallic waste is an important issue for the safety analysis of geological disposal facilities for transuranic (TRU) radioactive waste in Japan. The objective of this study is to clarify the gas-generation behavior of stainless steel and carbon steel in non-oxidizing alkaline synthetic groundwater (pH 12.8 and 10.5) at 30 °C simulating geological disposal environments. At pH 12.8, the observed gas-generation rate from stainless steel in the initial period of immersion was 1.0 × 102 Nml/m2/y and 1.0 × 10 Nml/m2/y after 200 days (N represents the standard state of gas at 0 °C and 1 atm). At pH 10.5, gas generation was not observed for 60 days in the initial period. At 60 days, the gasgeneration observed was 5.0 × 10 Nml/m2/y. After 250 days, the gas-generation rate approaches zero. At pH 12.8, the observed gas generation rate of carbon steel in the initial period of immersion was 1.5 × 102 Nml/m2/y and the gas generation rate began to decrease after 200 days. After 300 days, it was 25 Nml/m2/y. At pH 10.5, the gas generation rate in the initial period was 5.0 × 102 Nml/m2/y and was 1.0 × 10 Nml/m2/y after 200 days.

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