Portable Hydrogen Generation

Motivation

• Determine cost, safety, energy density, and overall feasibility of using ammonia borane in portable power generation applications
• Develop low-cost, portable systems that can deliver on-demand hydrogen to drive a fuel cell as a direct alternative to batteries

System comparison to DoE Targets for Portable Applications

R&D to develop high-performance energy storage systems (Aeropak system shown as baseline)

Materials and Techniques

• Ammonia borane (AB) hydrolysis (~9 wt.% hydrogen)
  • Reaction initiated with water addition
  • Suppresses toxic borazines vapors formed when AB is thermally decomposed
  • Challenge in eliminating the ammonia gas produced (compatibility with a proton exchange membrane fuel cell)

SEM images of catalysts used, from left to right, Amberlyst-15 (as-received), Amberlyst-15 (ball-milled), and 20% Platinum / 80% Carbon

• Characterization of catalyzed hydrolysis reaction (see: Ammonia Borane &: Sodium Borohydride)
  • Proton exchange resin used as a catalyst
  • Comparisons to traditional metal catalyst
• Material Processing
  • Platinum black and activated carbon mixed via ball milling
  • Amberlyst – 15: ball milled separately to a similar particle size

Experimental Setup

• Test the aspects of decomposition reaction that relate to portable operation with a PEM fuel cell
• Control of the water delivery, and reaction environment
• Measurements of temperature, pH, gas production rate, and gas purity

Experimental Results

• Gas Purity & Kinetics Studies:
  • Objective: determine activation energies and gas compatibility with PEM fuel cells
  • Gas chromatography used for hydrogen concentration
  • FTIR used to identify contaminate species
  • Amberlyst-15 eliminates ammonia production from AB hydrolysis and reduces activation energy by factor of ~5 compared to Pt/C catalyst

Accomplishments/Highlights

• Decomposed ammonia borane via catalyzed hydrolysis
• Tested gas purity and compatibility with PEM-fuel cells
• Characterized hydrolysis reaction kinetics of AB using various catalysts

Multimedia

Hydrolysis of AB with Amberlyst-15. Yield: 95% of theoretical, Reaction duration: 10 seconds, Exotherm: 5°C


Hydrolysis of AB with Pt/C. Yield: 85% of theoretical, Reaction duration: 3 minutes, Exotherm: 20°C

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Researchers