Nano-Structured Catalytic Material for Solar-Powered Biofuel Reforming

Abstract

The main goal of this project is to combine two renewable energy conversion technologies (low-temperature fuel cells and solarthermal collectors) to achieve synergies in terms of cost and energetic efficiency compared to systems based on a single energy source and energy conversion technology. Direct solar-to-electric energy conversion, such as photovoltaics, is currently not economically competitive with traditional electric power generation. Fuel cell technology using alcoholic fuel possibly generated from biomass (e.g. methanol) is not competitive in terms of costs either. The system proposed for this project is based on relatively cheap, commercially available hardware components (intermediate-temperature solar collector, pressurized gas tank, hydrogen-fed Proton Exchange Membrane (PEM) fuel cell) and benefits in terms of energetic efficiency from the cost-free supply of solar heat. By applying micro-fabrication technology and nano-scale structures (e.g. for catalytic surfaces), the efficiency of all individual system components and of the entire system can be increased drastically. The catalytic activity of micro-reactors containing this foam-like ceramic is tested in terms of their ability to convert alcoholic biofuel (e.g. methanol) to a hydrogen-rich gas mixture with low concentrations of carbon monoxide (up to 75% hydrogen content and less than 0.2% CO, for the case of methanol). This gas mixture is subsequently used in a low-temperature fuel cell, converting the hydrogen directly to electricity. A low concentration of CO is crucial to avoid poisoning of the fuel cell catalyst. Since conventional Polymer Electrolyte Membrane (PEM) fuel cells require CO concentrations far below 100 ppm and since most methods to reduce the mole fraction of CO (such as Preferential Oxidation or PROX) have CO conversions of up to 99%, the alcohol fuel reformer has to achieve initial CO mole fractions significantly below 1%. The catalyst and the porous ceramic reactor of the present study can successfully fulfill this requirement.