Hydrogen is a promising energy carrier in future energy systems. However, storage of hydrogen is a substantial challenge, especially for applications in vehicles with fuel cells that use proton-exchange membranes (PEMs). Different methods for hydrogen storage are discussed, including high-pressure and cryogenic-liquid storage, adsorptive storage on high-surface-area adsorbents, chemical storage in metal hydrides and complex hydrides, and storage in boranes. For the latter chemical solutions, reversible options and hydrolytic release of hydrogen with off-board regeneration are both possible. Reforming of liquid hydrogen-containing compounds is also a possible means of hydrogen generation. The advantages and disadvantages of the different systems are compared.

Chemical and Physical Solutions for Hydrogen Storage

Fuel processing for low-temperature and high-temperature fuel cells: Challenges, and opportunities for sustainable development in the 21st century

Dimethyl ether (DME) as an alternative fuel

Carbon supported platinum is commonly used as anode and cathode electrocatalyst in low-temperature fuel cells fuelled with hydrogen or low molecular weight alcohols. The cost of Pt and the limited world supply are significant barriers to the widespread use of these types of fuel cells. Moreover, platinum used as anode material is readily poisoned by carbon monoxide, present in the reformate gas used as H2 carrier in the case of polymer electrolyte fuel cells, and a byproduct of alcohol oxidation in the case of direct alcohol fuel cells. In addition, Pt alone does not present satisfactory activity for the oxygen reduction reaction when used as cathode material. For all these reasons, binary and ternary platinum-based catalysts and non-platinum-based catalysts have been tested as electrode materials for low temperature fuel cells. Palladium and platinum have very similar properties because they belong to the same group in the periodic table. The activity for the oxygen reduction reaction (ORR) of Pd is only slightly lower than that of Pt, and by addition of a suitable metal, such as Co or Fe, the ORR activity of Pd can overcome that of Pt. Conversely, the activity for the hydrogen oxidation reaction (HOR) of Pd is considerably lower than that of Pt, but by adding of a very small amount (5 at%) of Pt, the HOR activity of Pd attains that of pure Pt. This paper presents an overview of Pd and Pd-containing catalysts, tested both as anode and cathode materials for low-temperature fuel cells.

Palladium in fuel cell catalysis

▪ Abstract After a brief survey of fuel cell types, attention is focused on material requirements for SOFC and PEMFC stacks, with an introductory section on materials technology for reformers. Materials cost and processing, together with durability issues, are emphasized as these now dominate materials selection processes for prototype stack units. In addition to optimizing the cell components, increasing attention is being given to the composition and processing of the bipolar plate component as the weight and volume of the relevant material has a major influence on the overall power density and cost of the fuel cell stack. It is concluded that the introduction of alternative materials/processes that would enable PEMFC stacks to operate at 150–200°C, and IT-SOFC stacks to operate at 500–700°C, would have a major impact on the successful commercialization of fuel cell technology.

Recent Advances in Materials for Fuel Cells

Gasoline fuel cell systems

Industrial application of fuel cell technology requires suitable electrocatalysts. This is true for all different types of fuel cells. These catalysts are responsible for the oxidation of the fuel (i.e. hydrogen, hydrogen rich gases or methanol) as well as for the oxygen reduction. This paper focuses on solid polymer electrolyte fuel cell systems for mobile applications. Here the demands on the catalyst are most severe due to the low-temperature operating regime. Two system configurations are possible: either the carbon containing fuel is processed by a fuel converter to a hydrogen rich gas mixture and this in turn is fed into the fuel cell. Alternatively fuels such as methanol can be supplied directly into the fuel cell. In the first case, contaminations of CO in the feed gas have to be taken into account. These strongly absorbs on the surface of the catalysts (carbon-supported Pt or Pt-alloys) thereby inhibiting the hydrogen oxidation reaction. Electro-oxidation mechanisms of adsorbed CO as well as methanol—as an example for a direct fuel cell system—is discussed on Pt-Ru and other catalysts. Finally catalysts for methanol and hydrocarbon reforming reactions as well as for the shift reaction are reviewed.

Catalytic processes in solid polymer electrolyte fuel cell systems

Cold start simulations of a gasoline based fuel processor for mobile fuel cell applications

The catalytic material is applied to a carrier material (10a,10b,10c) which is formed as a cell and/or channel having monolithic structure made of ceramic or metal. The increase of the reaction surface per volume unit is by reduction of hydraulic cross-section and/or reduction of material wall thickness of the channel structure to create an increased cell thickness of the catalytic material. In an apparatus for catalytic conversion of a starting material, the starting material is brought into contact with a catalytic material between one of inlets of the apparatus and outlet of the apparatus, and the active reaction surface of the catalytic material is step-wisely or continuously increased per volume unit from the inlet to the outlet of the apparatus by the entering starting material.

Andreas Docter

Papers

Gasoline fuel cell systems

Catalytic processes in solid polymer electrolyte fuel cell systems

Cold start simulations of a gasoline based fuel processor for mobile fuel cell applications

Device for the catalytic conversion of a feedstock, particularely of a gas mixture

Modelling and dynamic simulation of a fuel cell system with an autothermal gasoline reformer