| A combinatorial method, based on fluorescence detection of electroactivity, was applied to the discovery and optimization of bifunctional electrocatalysts for the oxygen electrode in unitized regenerative fuel cells (URFC's). By using a consensus map generated from parallel screening, an electrocatalyst array containing five elements (Rh, Pt, Ru, Os, Ir) was simultaneously optimized for corrosion resistance and catalytic activity in both oxygen reduction and water oxidation. A ternary Pt-Ru-Ir catalyst identified by this method gave performance superior to the previously described PtIr binary catalyst. A detailed mechanistic study found that the addition of the oxophilic element ruthenium to the catalysts stabilized surface oxide species and accelerated the oxidative deprotonation of surface OH groups.; Ebonex was used as a supporting material to further study and optimize the bifunctional catalysts. A “hot zone” encompassing the most active supported catalysts was found around the same region where the most active unsupported catalysts were located on the consensus maps.{09}The amount of current generated by the supported catalysts (20wt% metal loading) was slightly more than the amount produced by the same weight of unsupported catalysts.; Other conductive supporting materials, Ti4O7 and Ti0.9Nb0.1O2, were also synthesized. The electrocatalyst prepared on Ti0.9Nb0.1O2 showed better electrochemical activity and stability as the porous oxygen electrode than those on Ebonex. Ac impedance measurements and transmission line modeling showed that these differences were due to the different electric behavior of the supports during the electrochemical process.; The goal of preparative-scale chiral separation has led to the design of a new generation of chiral stationary phases in which rigid cyclophanes were intercalated into high surface area lamellar solids. Neutral π-acceptor cyclophanes derived from 1,5-dinitronaphthelene and 1,4,5,8-naphthalenetetracarboxylic diimide were synthesized. The association of the cyclophanes with indole in solution was monitored by the UV-vis absorbance of charge transfer band, or the proton shifts in the 1HNMR spectra. Weak or no association was detected due to the poor π-acceptors in the synthesized cyclophanes. A method that ranks π-acceptor ability of different aromatic groups was devised, which justified the low binding constants of the synthesized cyclophanes, and also identified anthraquinone as a strong π-acceptor. |
