39. Efficient Fuel and Solar Cells
(l.) Ulrich Wiesner (r.) Frank DiSalvo
Ulrich B. Wiesner, Materials Science and Engineering, Francis J. DiSalvo, Chemistry and Chemical Biology, and their research colleagues showed that a one-pot process could make more efficient materials for fuel cells and solar cells. In a fuel cell, a material with nanoscale pores offers more surface area over which a fuel can interact with a catalyst. In a solar cell, a porous material similarly offers more surface area over which light can be absorbed, so more of it is converted to electricity. Porous materials have previously been made on hard templates of carbon or silica or by using soft polymers that self-assemble into a foamy structure. Hard porous templates are tricky to make, and while the polymer approach is easier and creates a good structure, the metal oxides must be heated to high temperatures to crystallize fully, which causes the polymer pores to collapse. Wiesner and DiSalvo combined the best of the two approaches, creating porous films of crystalline metal oxides by using a soft block copolymer called poly(isoprene-block-ethylene oxide), or PI-b-PEO, that carbonizes when heated to high temperatures in an inert gas, providing a hard framework around which the metal oxide crystallizes. Subsequent heating in air burns away the carbon. The researchers call this approach CASH (combined assembly by soft and hard chemistries). The resulting materials were examined by electron microscopy, x-ray diffraction, and a variety of other techniques, all of which confirmed a highly crystalline structure and a uniform porosity. The next step is to apply the CASH process to the creation of porous metals.