Reformers

Anode design is simpler when hydrogen is the fuel, compared to anodes that use organic fuels. However, hydrogen must currently be stored as a high-pressure gas in large, expensive containers. Alternatively, liquid hydrocarbons can be used to carry hydrogen. In that case, a reformer is used to produce and provide clean hydrogen (free from significant CO and sulfur poisons if Pt is the anode). Cleaning the hydrogen requires a number of steps.

  • Steam Reformation
    • fuel is combined with water to form carbon dioxide, carbon monoxide and hydrogen over a catalyst (Nickel)
      • this mixture must then be purified before introduction into the fuel cell
    • operation temperature is higher than 650°C
    • this high temperature requirements limit steam reformers to use in large fixed installations using solid oxide fuel cells (SOFC)
  • Catalytic Partial Oxidation(Air Reformers)
    • oxygen from air is directly combined with the fuel to produce CO2 and H2
    • lower operation temperatures (as low as 350°C for methanol
    • avoids the water management issues of steam reformation
    • noble metal catalysts are required
    • more than 30% of the free energy of combustion is lost for methanol in the non-electrolytic formation of CO2
  • Combine reformation and oxidation
    • more complex controls

Even though reformer operation temperatures have been lowered to 350° these reformer temperatures are still too high for many smaller applications to which fuel cells would be otherwise well-suited. However, if the challenges in storing hydrogen cannot be overcome, the reformer may be necessary. Currently, all the automotive fuel cell R&D assumes that the hydrogen storage problem will be solved or that 10,000 psi gas tanks can be cheaply produced. Others assume that it is more reasonable to carry liquid fuels and put a complex reformer on board. If this option is to be viable, there is a great impetus to develop reformer and water-gas shift catalysts that operate more efficiently and at lower temperatures.

  • Anode materials that function at lower (less positive) potentials are likely to be excellent catalysts for water gas-shift reactors at low temperatures.
  • Both anodes and reformers must activate the fuel to dehydrogenation and must provide oxygen to readily oxidized carbon to CO2.
  • Such characteristics are already embodied in the new anode materials that we have studied at CFCI, and so are excellent candidates for reformer catalysts.
  • We are collaborating with others to evaluate the utility of the above intermetallics in reformer and water-gas shift applications.