Final Report: Accelerated Hydrogen Diffusion Through Glass Microspheres: An Enabling Technology for a Hydrogen Economy

EPA Grant Number: R830420C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R830420
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Center for Environmental and Energy Research (CEER)
Center Director: Earl, David A.
Title: Accelerated Hydrogen Diffusion Through Glass Microspheres: An Enabling Technology for a Hydrogen Economy
Investigators: Shelby, James , Hall, Matthew M.
Institution: Alfred University
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2002 through February 28, 2004
RFA: Targeted Research Center (2002) Recipients Lists
Research Category: Targeted Research , Congressionally Mandated Center

Objective:

A completely new phenomenon based on photo-enhanced diffusion of hydrogen in glass has been discovered at Alfred University.  Application of this phenomenon to glass microspheres for storage of hydrogen can provide the enabling technology for replacement of traditional methods for storing and transporting hydrogen in high pressure containers or at cryogenic temperatures with lighter, cheaper, safer technology.  Use of hydrogen either for combustion or in fuel cells will drastically alter the transportation industry, radically reduce smog, and save hundreds of billions of dollars in cost of imported oil.

The specific objectives of this research project were to:  (1) provide data needed to demonstrate that light enhanced diffusion can be optimized to produce rates sufficient for commercial applications; and (2) optimize the various experimental parameters to provide a highly efficient combination of material and light source.

Summary/Accomplishments (Outputs/Outcomes):

Methods

The saturation/outgassing method, which closely approximates the conditions that will occur in many commercial applications of this technology, was used to determine the rate of release of gasses that have been introduced into the glass samples previously by either heating in the appropriate atmosphere or by exposing the samples to light.  The details of these methods can be found in the M.S. thesis by Kenyon (1998).  The apparatus used in that study was used in this work.

A 250 watt infrared lamp, which is a broad spectrum lamp with considerable emission in the visible, was used as the light source in this research project.  Optical filters were used to define specific irradiation wavelength ranges to determine the most effective wavelengths for inducing this effect.

Preliminary results suggested that no further enhancements in diffusivity are gained by increasing the intensity of the light beyond some level at which the process is fully activated. The effect of lower intensities, which may provide a path for controlling the release rate of hydrogen from the microspheres during application, was studied by using a variable voltage transformer in series with the light source.

Glasses used in the earlier studies were based on commercial sodium borosilicate compositions.  Borosilicate glasses differ in morphology at the 50 to 500 nm scale from most other commercial glasses, with a microstructure consisting of two interspersed glasses of very different composition and properties.  Because the glasses studied in earlier work have this morphology, it was not known if the enhancement of diffusivity was in some way related to that microstructure or if glasses that are homogeneous at this level would also exhibit the enhanced diffusion effect.  It follows that determination of the effect of glass composition on the enhancement effect was needed to increase understanding of the mechanism responsible for this phenomenon.  Furthermore, because borosilicate glasses are much more expensive than many other types of glasses, the potential exists for considerable cost reduction of an operational system for hydrogen storage if other cheaper glasses can be used.  In particular, soda-lime-silicate glasses were included in this research project to determine if they can replace the more expensive borosilicate glasses.  A small series of other glasses having a systematic compositional variation was included to determine the effect of the content of the glassformer on the process.  A survey of other, widely different types of glasses, including some non-silicate glasses (borates or phosphates), also has been carried out to ensure that the basic nature of the host glass does not radically alter the acceleration behavior.

Irradiation of the colorless, as-received glass does not yield a significant enhanced diffusion effect.  The glasses used in the earlier work were doped with either iron or copper oxides.  Although both dopants cause strong enhanced diffusion effects, the use of iron oxide produced a greater effect.  A number of other dopants were studied in the present work to determine the interaction between the source spectrum and the absorption spectrum of the glass.  In particular, dopants that only absorb in the infrared (e.g. Yb3+), those which absorb strongly at the ultraviolet end of the spectrum (e.g. Ti3+), and those which exhibit broad absorption bands (e.g. Ni2+ and Co2+) in the near infrared (NIR) were studied.

Results

Results of the present study (Rapp, 2004; Rapp and Shelby, 2004) demonstrated that photo-induced outgassing of dissolved hydrogen from glass occurs at much faster rates than thermally induced outgassing from identical samples.  It has been proven that addition of absorbing species is necessary for rapid release of hydrogen (Figure 1).

Figure 1. Comparison of Outgassing Curves for NiO  Doped CGW-7070 Glass With the Undoped Glass.

Figure 1.  Comparison of Outgassing Curves for NiO Doped CGW-7070 Glass With the Undoped Glass

In addition to the previous discovery that iron ions (ferrous state) are highly efficient dopants for creating the photo-enhanced hydrogen diffusion effect, it also has been shown that iron and cobalt ions are equally effective in producing this effect (Figure 2).  Further heat treatments in hydrogen reduce the nickel and cobalt ions to the atomic state, where they agglomerate to form colloids.  The glass then becomes black, with an increased NIR absorption.  This treatment results in a more efficient dopant than found for any of the ionic species.

Figure 2. Comparison of Outgassing Curves.

Figure 2.   Comparison of Outgassing Curves for NiO and Fe2O3 Doped CGW­7070 Glass With the Undoped Glass

It was determined that a commercial borosilicate glass, designated as CGW-7070, is the most efficient glass for our purpose.  This glass is closely followed by CGW-7740 borosilicate glass, which is commonly known as Pyrex®.  Soda-lime-silicate glasses were less effective in producing photo-enhanced hydrogen diffusion effects.
It was determined that the outgassing rate is linearly proportional to light intensity, after a minimum intensity required before any effect occurs.  This discovery will provide a method for controlling the flow rate of hydrogen from the microspheres to the fuel cell.

Surprisingly, an aging effect was found for the iron-doped glasses, which may actually improve their performance with repeated cycles of saturation-outgassing.  In other words, the efficiency of the overall process will actually increase with the number of fill/release cycles.  This finding is in direct contrast with results for metal hydrides, which typically degrade in performance with repeated filling/release cycles.

It has been clearly established that this process is induced absorption specifically in the NIR region of the spectrum, with the maximum effect for wavelengths between 800 and 2,000 nm.  Coupling of a light source rich in these wavelengths with dopants that strongly absorb in this region will result in a maximum photo-enhanced hydrogen diffusion effect.

Although no attempts were made during this study to produce hollow glass microspheres from the doped borosilicate glasses, it was demonstrated that solid glass microspheres can easily be produced from these materials.

Conclusions

Results of this study indicate that hydrogen storage in hollow glass microspheres doped with the appropriate absorbing species are a viable contender for storage of hydrogen for automotive applications.

References:

Kenyon BE. Gas solubility and accelerated diffusion in glasses and melts. M.S. Thesis. Alfred University, 1998.


Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 3 publications 1 publications in selected types All 1 journal articles
Other center views: All 34 publications 8 publications in selected types All 6 journal articles
Type Citation Sub Project Document Sources
Journal Article Rapp DB, Shelby JE. Photo-induced hydrogen outgassing of glass. Journal of Non-Crystalline Solids 2004;349:254-259. R830420 (Final)
R830420C001 (Final)
R830420C006 (Final)
  • Abstract: Science Direct Abstract
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  • Supplemental Keywords:

    sustainable industry/business, technology for sustainable environment, clean technologies, environmental materials, glass technology, energy, environmental engineering, alternative energy source, ceramic materials, clean energy, renewable energy, green building design, hydrogen, diffusion, hollow glass microspheres, photo-enhanced hydrogen diffusion,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Technology, Technology for Sustainable Environment, Environmental Engineering, NOx reduction, clean energy, energy conservation, clean technologies, cleaner production, sustainable development, environmental conscious construction, clean manufacturing, energy efficiency, energy technology, emissions control, fuel cell design, environmentally conscious design, polymer fuel cell

    Relevant Websites:

    http://ceer.alfred.edu/ Exit
    http://ceer.alfred.edu/Research/glassspheres.html Exit

    Progress and Final Reports:

    Original Abstract
  • 2003 Progress Report

  • Main Center Abstract and Reports:

    R830420    Center for Environmental and Energy Research (CEER)

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