Gary Pattrick

CO oxidation: Deactivation of Au/TiO2 catalysts during storage

In a study of the phenomenon of catalyst deactivation during storage, Au/TiO2 catalyst was stored under various conditions, viz. vacuum, nitrogen, air, refrigeration, dark, and light, and tested for CO oxidation activity at regular intervals. The data shows that the catalyst deactivates under all the storage conditions over 12 months and that storage in vacuum significantly enhances the rate and extent of deactivation. Storage in light accelerates the deactivation. The catalyst appears to deactivate through a combination of Au(III) reduction, Au nanoparticle agglomeration, loss of surface hydroxyl groups, loss of surface moisture, and accumulation of surface carbonates and formates. The rate and extent of catalyst deactivation can be limited by storing the catalyst in the dark at sub ambient temperature (refrigerator) and under inert atmosphere.

An unconventional Au/TiO2 PROX system for complete removal of CO from non-reformate hydrogen

Au-based catalysts, generally known for high activity in the selective catalytic oxidation of CO to CO2 at ambient temperatures, can play a significant role in increasing the fuel cell system’s CO tolerance. In this work, an unconventional CO tolerance method, using an Au/TiO2 “guard bed”, has been investigated. The system is unconventional in the sense that it does operate as a PROX catalyst, but not in a traditional reformer system configuration. Instead, it has been developed to completely remove CO onboard the vehicle over a wide range, ppm to percentage levels, from impure pressurized H2-rich gas, i.e. from partially enriched H2 that would be stored in a fuel tank/cylinder but that would have some CO contamination and would essentially be dry. This set up will allow a reduction in the cost and complexity of conventional “off-board” hydrogen enrichment. The system CO tolerance obtained with the Au/TiO2 system was compared with state of the art PtRu/C and PtMo/C CO tolerant anode technologies. Catalytic effectiveness in the removal of CO has been directly monitored by both direct analytical measurements and by monitoring the operation of a laboratory fuel cell to which the purified hydrogen stream was passed.

Mild and Low-Cost Synthetic Process for Monodispersive Platinum Nanoparitcles on Carbon Aerogel

A mild synthetic process using formic acid as the reduction agent was applied to prepare 40 wt% Pt/carbon aerogel (CA) electrocatalyst. The as-prepared sample was characterized by transmission electron microscopy (TEM) and electrochemical measurements. The results exhibit Pt nanoparticles with narrow particle size distribution are dispersed throughout carbon aerogel structure. Moreover, the Pt/CA catalyst has smaller Pt nanoparticle mean size than Johnson Matthey HiSpecTM 4000 (JM4000). The electrochemical measurement results indicate that the Pt/CA catalyst with Pt loading of 40 wt% possesses similar electrochemical surface area (ESA) value and oxygen reduction reaction (ORR) activity as JM4000.

Characterization and Synthesis of PtRu/C Catalysts for Possible use in Fuel Cells

Mixed metal nanocatalysts containing platinum and ruthenium on a carbon support were synthesized for possible use in direct methanol fuel cells (DMFC). the synthesis of these catalysts, as described in the literature, is a standard impregnation method of the metal salts, followed by reduction. The reduction can be carried out in a number of ways - either by the addition of a liquid reducing agent or by passing a reducing gas over the filtered and dried catalyst. In this study, PtRu/C catalysts were prepared by reduction with various possible reducing agents, i.e. formaldehyde, formic acid and hydrogen gas at relatively low (923 K) and high (1 173 K) temperatures. The catalyst material was tested by transmission electron microscopy (TEM), X-ray diffraction (XRD) and electro chemical methods in order to determine the particle size, alloy formation and catalytic activity of the material. It was found that milder reducing agents led to smaller particle sizes of the metal particles on the carbon support. Reduction conditions were also found to significantly influence the properties of the catalyst. A variety of different metallic, hydrated and oxide species of the precious metal particles are possible. Temperature programmed reduction (TPR) was used to investigate the relative oxidation state of the metal particles.

CATALYSIS AND CAPACITANCE OF NANOSTRUCTURED GOLD SPONGES

In the present paper we describe the catalytic properties and electrolytic double-layer capacitance of nano-structured, mesoporous gold sponges. These materials are effective catalysts for CO oxidation, and for the selective catalytic conversion of NOx. The possible application of mesoporous gold in electric double layer capacitors is premised on its high surface area, corrosion resistance and excellent electrical conductivity. The niche, if any exists, would be in high-efficiency, and high-power density ultra-capacitors for top-end consumer appliances.