Neil J. Lawrence

Defect Engineering in Cubic Cerium Oxide Nanostructures for Catalytic Oxidation

Traditional nanostructured design of cerium oxide catalysts typically focuses on their shape, size, and elemental composition. We report a different approach to enhance the catalytic activity of cerium oxide nanostructures through engineering high density of oxygen vacancy defects in these catalysts without dopants. The defect engineering was accomplished by a low pressure thermal activation process that exploits the nanosize effect of decreased oxygen storage capacity in nanostructured cerium oxides.

Pd/CeO2−x Nanorod Catalysts for CO Oxidation: Insights into the Origin of Their Regenerative Ability at Room Temperature

The decrease in the activity of a catalyst after use is a persistent challenge in the chemical industry. We report that palladium‐decorated ceria (Pd/CeO2−x, in which 0≤x<0.5) nanorod catalysts demonstrate regenerative ability for carbon monoxide oxidation at room temperature. Pd/CeO2−x catalysts with 75 % decreased catalytic activity can be regenerated and restored almost 100 % of their original catalytic activity by exposing them to ambient conditions for 24 h. X‐ray spectroscopy studies of the atomic structures and oxidation states of palladium in the catalyst found that the formation of disordered palladium oxide is partly accountable for its observed regenerative catalytic property.

Influence of nanostructured ceria support on platinum nanoparticles for methanol electrooxidation in alkaline media

The catalytic activity of platinum (Pt) nanoparticles (NPs) towards methanol electrooxidation in alkaline media was demonstrated to be dependent on their interactions with their nanostructured ceria support. Ceria nanorods (NRs) with diameters of 5 to 10 nm and lengths of 15 to 50 nm as well as ceria NPs with diameters of 2 to 6 nm were applied as supports for similarly sized Pt NPs with diameters of 2 to 5 nm. Cyclic voltammetry data showed that Pt NPs supported on ceria NPs exhibited a 2-to-5-fold higher catalytic current density versus ceria NRs. X-ray photoelectron spectroscopic data indicated that Pt NPs deposited onto ceria NRs were disproportionally composed of oxidized species (Pt2+, Pt4+ and Pt–O–M) rather than Pt0 while Pt NPs on ceria NPs mainly consisted of Pt0. Stronger metal-support interactions between Pt NPs and ceria NRs are postulated to induce preferential oxidation of Pt NPs and consequently decrease the catalytic sites and overall activity.

Controlling E. coli Adhesion on High-k Dielectric Bioceramics Films using Poly(amino acid) Multilayers

The influence of high-k dielectric bioceramics with poly(amino acid) multilayer coatings on the adhesion behavior of Escherichia coli (E. coli) was studied by evaluating the density of bacteria coverage on the surfaces of these materials. A biofilm forming K-12 strain (PHL628), a wild-type strain (JM109), and an engineered strain (XL1-Blue) of E. coli were examined for their adherence to zirconium oxide (ZrO(2)) and tantalum oxide (Ta(2)O(5)) surfaces functionalized with single and multiple layers of poly(amino acid) polyelectrolytes made by the layer-by-layer (LBL) deposition. Two poly(amino acids), poly(l-arginine) (PARG) and poly(l-aspartic acid) (PASP), were chosen for the functionalization schemes. All three strains were found to grow and preferentially adhere to bare bioceramic film surfaces over bare glass slides. The bioceramic and glass surfaces functionalized with positively charged poly(amino acid) top layers were observed to enhance the adhesion of these bacteria by up to 4-fold in terms of bacteria surface coverage. Minimal bacteria coverage was detected on surfaces functionalized with negatively charged poly(amino acid) top layers. The effect of different poly(amino acid) coatings to promote or minimize bacterial adhesion was observed to be drastically enhanced with the bioceramic substrates than with glass. Such observed enhancements were postulated to be attributed to the formation of higher density of poly(amino acids) coatings enabled by the high dielectric strength (k) of these bioceramics. The multilayer poly(amino acid) functionalization scheme was successfully applied to utilize this finding for micropatterning E. coli on bioceramic thin films.

Resonant Photoemission Observations and DFT Study of s–d Hybridization in Catalytically Active Gold Clusters on Ceria Nanorods

Gold clusters have garnered intense interest because of their unusual catalytic activities towards chemical reactions of industrial importance. Electronic structures of oxide supported gold clusters can provide critical clues to the mechanisms for their catalytic activity. Gold atoms possess an electronic configuration of [Xe] 4f145d106s1. However, both relativistic effects and 5d band upshift of gold clusters result in a theoretically expected hybridization of the 5d and 6s orbitals. These s-d hybridized orbitals are expected to, essentially, increase the number of free d states (or d holes) available for bonding with incoming reactant molecules, thus lowering the transition state energy and promoting the reactions.

Preparation and characterization of Pt/Pt:CeO2-x nanorod catalysts for short chain alcohol electrooxidation in alkaline media

Multi-functional anode catalysts composed of platinum (Pt) nanoparticles electrodeposited on 2 wt% Pt decorated ceria (Pt:CeO2−x) nanorod supports were shown to enhance the alkaline electrocatalytic oxidation of methanol, ethanol and n-butanol over electrodeposited Pt nanoparticles alone or ones supported with pure ceria nanorods. The Pt:CeO2−x nanorod support was demonstrated to increase the current density of the investigated alkaline electrooxidation of methanol, ethanol and n-butanol by more than 30% over the other two catalysts.

Rapid Analysis of Copper Ore in Pre-Smelter Head Flow Slurry by Portable X-ray Fluorescence.

Copper laden ore is often concentrated using flotation. Before the head flow slurry can be smelted, it is important to know the concentration of copper and contaminants. The concentration of copper and other elements fluctuate significantly in the head flow, often requiring modification of the concentrations in the slurry prior to smelting. A rapid, real-time analytical method is needed to support on-site optimization of the smelter feedstock. A portable, handheld X-ray fluorescence spectrometer was utilized to determine the copper concentration in a head flow suspension at the slurry origin. The method requires only seconds and is reliable for copper concentrations of 2.0–25%, typically encountered in such slurries.