Optical high-throughput screening for activity and electrochemical stability of oxygen reducing electrode catalysts for fuel cell applications.

A fluorescence-based electro-optical high-throughput method and setup for testing the oxygen reduction reaction (ORR) activity and electrochemical stability of 60 materials in parallel is described. We present thus a quantitative method for activity measurements for ORR-catalysts by optical fluorescence data acquisition. The fluorescence behavior of fluorescein, phloxine B, and umbelliferone as indicators is presented. The effect of oxygen concentration, saturation, and supply on electrochemical response is presented. Corrections for internal resistance differences and intensity differences are described. The final method allowed position independent determination of activities on the working-electrode library, containing up to 60 different electrocatalysts. A total of 378 selected mixed oxides have been studied. Cu/Ni/Mn and Co/Ni/Mn oxides proved electrochemically most active and comparable to a Pt-containing reference catalyst.

Search for new catalysts for the oxidation of SO2.

The focus of this paper is the search and characterization of novel catalysts for the gas phase oxidation of concentrated SO2 for the production of sulfuric acid. Modern high-throughout (HT) methods such as emissivity corrected Infrared Thermography (ecIRT) and automated synthesis techniques were used for the synthesis and activity measurements of the samples. In addition a plug flow reactor that uses UV-vis online analytics for the quantification of the SO2 conversion was designed, built and used for validation of the HT results. The study started with a highly diverse search space of elemental compositions designed for potential discovery. About a thousand samples were synthesized using sol-gel recipes and screened for catalytic SO2 oxidation activity over a temperature range of 330-450 °C. Several novel catalyst systems were discovered during the screening process and the most interesting systems were further characterized. The most important doping effects on activity found were the influence of bismuth and selenium doping on standard sulfuric acid catalysts, the activity gain of chromium based catalysts caused by the doping with antimony and the activity gain of chromium as well as iron and vanadium based catalysts caused by the doping with tin.

Combinatorial development of novel Pd based mixed oxide catalysts for the CO hydrogenation to methanol.

In a combinatorial study numerous palladium containing mixed oxides were synthesized by a sol-gel approach and screened for their catalytic activity toward methanol synthesis from synthesis gas. Several materials exhibited higher yields than comparable supported catalysts. Titanium based materials showed to be the most promising catalytic materials, which exhibited good selectivities for temperatures below 265 °C. The materials investigated are characterized by high specific surface areas and high pore volumes which seem to have a beneficial effect on the reactivity.

Fluorescence-based high throughput screening for noble metal-free and platinum-poor anode catalysts for the direct methanol fuel cell.

We describe here the results of a high throughput screening study for direct methanol fuel cell (DMFC) anode catalysts consisting of new elemental combinations with an optical high-throughput screening method, which allows the quantitative evaluation of the electrochemical activity of catalysts. The method is based on the fluorescence of protonated quinine generated during electrooxidation of methanol. The high-throughput screening included noble-metal free binary and ternary mixed oxides of the elements Al, Co, Cr, Cu, Fe, Mn, Mo, Nb, Ni, Ta, Ti, Zn, and Zr in the oxidized form as well as after prior reduction in hydrogen. In addition 318 ternary and quaternary Pt-containing materials composed out of the mixed oxides of Bi, Ce, Co, Cr, Cu, Fe, Ga, Ge, In, La, Mn, Mo, Nb, Nd, Ni, Pr, Sb, Sn, Ta, Te, Ti, V, Zn, and Zr with a molar Pt-ratio of 10% and 30% were screened. Validation and long time experiments of the hits were performed by cyclovoltammetry (CV). The microstructural stability of the electrode preparations of the lead compositions was studied by X-ray diffraction (XRD) pattern analysis.

High-throughput screening of nanoparticle catalysts made by flame spray pyrolysis as hydrocarbon/NO oxidation catalysts.

We describe here the use of liquid-feed flame spray pyrolysis (LF-FSP) to produce high surface area, nonporous, mixed-metal oxide nanopowders that were subsequently subjected to high-throughput screening to assess a set of materials for deNO(x) catalysis and hydrocarbon combustion. We were able to easily screen some 40 LF-FSP produced materials. LF-FSP produces nanopowders that very often consist of kinetic rather than thermodynamic phases. Such materials are difficult to access or are completely inaccessible via traditional catalyst preparation methods. Indeed, our studies identified a set of Ce(1-x)Zr(x)O(2) and Al(2)O(3)-Ce(1-x)Zr(x)O(2) nanopowders that offer surprisingly good activities for both NO(x) reduction and propane/propene oxidation both in high-throughput screening and in continuous flow catalytic studies. All of these catalysts offer activities comparable to traditional Pt/Al(2)O(3) catalysts but without Pt. Thus, although Pt-free, they are quite active for several extremely important emission control reactions, especially considering that these are only first generation materials. Indeed, efforts to dope the active catalysts with Pt actually led to lower catalytic activities. Thus the potential exists to completely change the materials used in emission control devices, especially for high-temperature reactions as these materials have already been exposed to 1500 degrees C; however, much research must be done before this potential is verified.

Visible-light detoxification and charge generation by transition metal chloride modified titania.

Amorphous microporous metal oxides of titanium (AMM-Ti) modified with chlorides of PtIV, IrIV, RhIII, AuIII, PdII, CoII, and NiII have been prepared by the sol-gel method and characterized by various surface analytical methods. These hybrid AMM-Ti powders are catalysts for the photodegradation of 4-chlorophenol (4-CP) in aqueous solution when illuminated with visible (lambda > or = 400 or 455 nm) or UV (lambda > or = 335 nm) light. The initial rate depends on the dopant level and is highest at 3.0% Pt in the case of PtIV/AMM-Ti. When employed in a photoelectrochemical cell, the activity spectrum of the photocurrent extends downward to about 600 nm, as does the photodegradation of 4-CP. It is suggested that the metal salt acts as a redox-active chromophore, transmitting the photogenerated charges to the amorphous matrix.