1. Sol-gel synthesis of porous metal oxides sorbents
Sol-gel processing refers to the fabrication process of ceramic materials by preparation of a sol, gelation of the sol, and removal of the solvent. Xerogels are obtained by drying the gels through evaporation at normal conditions under which capillary pressure causes shrinkage of the gel network, while areogels are produced by drying the wet gels at supercritical conditions where the liquid-vapor interface is eliminated, and relatively little shrinkage of the gel network occurs. Active adsorption sites are introduced into the surface of xerogels and areogels to enhance the selectivity and adsorption capacity through formation of p-complexation and other weak chemical bonds. Sol-gel process offers a high flexibility to tailor both pore texture and surface functional groups of xerogels and areogels for specific applications by manipulating the synthesis conditions. Existing research projects in this direction include sorbents for deep desulphurization of transportation fuels, getter materials for radionuclides immobilization, natural gas purification, and carbon monoxide removal from hydrogen.
2.Microwave heating synthesis of metal organic frameworks
Metal organic framework (MOF) is a novel crystalline nanoporous material that consists of metal atoms occupying the vertices of a lattice, with the lattice size, porosity, and chemical environment defined by the organic linker molecules that bind the metal atoms into a robust periodic structure. MOFs that are generally synthesized through hydrothermal method have found applications in hydrogen and methane storage, gas separation and purification. New synthesis approach with the assistance of microwave heating is being explored to prepare MOFs for new applications including waste water treatment and air pollution control.
3.Sulfur and carbon monoxide tolerant fuel cell electrocatalysts
Carbon monoxide and sulfur levels in hydrogen produced by reforming hydrocarbons fuels must be reduced for operation of proton exchange membrane (PEM) fuel cells with platinum based electrocatalysts. The chemically adsorbed CO prevents the dissociative electrosorption of hydrogen and dramatically lowers the cell potential produced by the membrane electrode assembly since a much higher anode potential is required to sustain the rate of hydrogen electroxidation. While the sulfur compounds in hydrogen strongly and irreversibly adsorb on active sites of platinum and permanently poison the electrocatalysts. Searching for sulfur and carbon monoxide tolerant catalysts with high hydrogen oxidation activity represents one of the major research efforts in fuel cell catalysts for PEM fuel cell. Unsupported and supported nickel promoted ruthenium sulfide (Ni x Ru 1-x S 2 ) catalysts are being prepared with both flash pyrolysis and precipitation methods, and will be evaluated in a PEM fuel cell unit.
