Nanotechnology for Energy, Environment, Healthcare and Industry : Session II
Program Organizers: Gary Pickrell, Virginia Tech; Navin Manjooran, Siemens Corporation
Monday 2:00 PM
October 8, 2012
Room: Room 312
Location: David L. Lawrence Convention Ctr
Session Chair: Brian Scott, Virginia Tech
2:00 PM
Transmission Electron Microscope Study of Shape-Directed Platinum Nanoparticles towards Catalysis: Ross Grieshaber1; Judith Yang1; 1University of Pittsburgh
Platinum nanoparticles have been shown to be quite effective catalysts, especially in the realm of fuel cell development. Tailoring the synthetic recipe of nanoparticles allows for strict size dispersions, that combined with tight morphologic control allow for very specific nanoparticles to be grown for use in catalysis where selectivity is important. In this research, platinum nanoparticles were synthesized via an inverse-micellar process, where metal salts are reduced in a polyol solvent. Shape directing agents are added to the reaction mixture to elicit various morphological shapes. Particular nanoparticle morphologies have various facets in dominance, such as (100) and (111) for cubic and octahedral, respectively. TEM is used to characterize the shape and morphological distribution of as-synthesized nanoparticles. An intimate understanding how nanocatalysts’ shape morphologies are affected by synthesis, reaction, and support conditions is crucial to the success of coherent design of catalysts in the future and beyond.
2:20 PM
A New Architecture for Robust Nano-Catalysts: Palladium on Hierarchical Carbon Structures: Hema Vijwani1; Sharmila Mukhopadhyay1; 1Wright State University
Catalytic activity can be significantly enhanced if the exposed surface area in a given volume is increased. This project demonstrates such enhancement using a palladium-graphite system supported on hierarchical graphitic nanostructures. Palladium-nanoparticles are deposited on porous carbon-foam substrates whose surface area has been increased by orders of magnitude through the attachment of carbon nanotubes. This type of structure can lead to unprecedented miniaturization of catalytic devices. Moreover, the nanoparticles and nanotubes are structurally durable, and remain attached to the base support after long periods of rapid rotation in water that indicates lower risk of material degradation and/or environmental. Fabrication issues of these structures will be presented along with microstructure and spectroscopic analysis. The results suggest potential adaptation of these hybrid structures in robust catalytic devices such as sensors, water purification systems, fuel cell electrodes and hydrogen storage sponges. Electrochemical behavior and water purification capabilities of these structures are being investigated.
2:40 PM
Magnetic Activate Carbon Nanocomposites for Water Purification: Allen Apblett1; Tarek Trad2; 1Oklahoma State University; 2The University of Texas at Brownsville
Green nanotechnology requires maximizing the potential benefits of nanotechnology for solving environmental problems while minimizing the environmental impact of nano-based processes. Nanoparticles have been demonstrated to have useful absorption and catalytic properties but it is difficult to take advantage of these properties in the real world due to their small size that makes it difficult to prevent their escape to the environment. We have addressed this challenge by utilizing the pyrolysis of waste cellulose/metal salt mixtures to generate nanoparticles embedded in and organic contaminants from water.
3:00 PM
Physicochemical Characterization of Cerium Particles Generated by Combustion of Ce-Doped Diesel Fuel: Robert Willis1; Kristin Bunker2; Traci Lersch2; Gary Casuccio2; Eric Grulke3; Natalia Mandzy3; Joseph Conny4; Michael Lewandowski1; Jason Weinstein1; Jonathan Krug1; Kasey Kovalcik1; David Nash1; 1Environmental Protection Agency; 2RJ Lee Group; 3University of Kentucky; 4National Institute of Standards and Technology
Diesel engines emit large amounts of soot which degrades air quality and harms public health. Nanoscale metal-oxide fuel-borne catalysts (FBCs) have been shown to reduce soot emissions and improve fuel efficiency. FBCs utilizing nano-sized cerium oxide (ceria) particles are used in other countries, but are not approved for on-road use in the US. The EPA’s Nanomaterial Research Strategy has targeted ceria as a nanomaterial of concern due to the potential for human and ecosystem exposure to nanoceria particles released to the atmosphere.In order to understand the exposure potential and environmental fate of nanoceria particles from use of FBCs, the EPA is conducting research to characterize the morphology, composition, and size distribution of cerium-rich particles generated by combustion of ceria-doped fuel. We will discuss results obtained using a nano-MOUDI™ cascade impactor to collect size-resolved particulate samples on filters (analyzed by ICP-MS) and TEM grids (analyzed with high-resolution electron microscopy).
3:20 PM Break
3:40 PM
Quantitative STEM Technique for Counting Numbers of Atoms in Nano-Catalysts: Long Li1; Zhongfan Zhang1; Judith Yang1; 1University of Pittsburgh
Catalysis is critical to wide variety of essential technologies, including energy generation, energy storage, sustainability, environmental protection and water purification. Performance of nano-catalysts depends intimately to their supported 3-D structures. STEM high-angle annular dark-field imaging is widely used in characterizations of supported metallic nanoparticles (NPs). We have developed a method determining numbers of atoms in NPs via quantitative-STEM (QSTEM) imaging from the high-angle scattered (>=100mrad) electrons which leads to an incoherent interpretation of images. The HAADF detector efficiency is measured under free-lens control, detector semi-inner/outermost angles of 100.3/252.1mrad, calibrated with STEM EDP of Au(100). Au NPs on an ultra-thin C-grid were characterized by this QSTEM technique. The average size of Au NPs is 0.9±0.2 nm with average 27±25 Au-atoms. The large range (±25atoms) of the average atom number indicates a variety of 3-D shapes of Au NPs even though they have a relatively monodispersive size distribution at the 2-D projection.
4:00 PM
Clustering Theory Evaluation for Thermal Conductivity Enhancement of Titania Nanofluid: Azadeh Ghadimi1; Hendrik Simon Cornelis Metselaar1; 1University Malaya
Nanofluid as a future cooling fluid attracted a wide span of application due to its great capability of heat dissipation. Nanofluid is a suspension of nanoparticles in a base fluid which often requires stabilization processing. In this study, 0.1%wt/v of TiO2 nanoparticles were mixed with distilled water. Three hours ultrasonication was used to prepare samples. Sodium lauryl sulfate(0.01-0.2)%wt/v and pH(10-12) were used as stability controlling parameters in order to verify thermal conductivity and particle size of nanofluid. Central composite design(CCD) and response surface methodology(RSM) were used to develop a model as well as defining the optimum condition with design of experiments(DOE). Amongst the variety of theories, clustering and agglomeration proved to be responsible for increasing thermal conductivity with rising particle size among different nano-suspensions. Results revealed that optimum conditions is located at high pH and low SDS concentration in which high thermal conductivity will be accompanied with larger particle sizes.
4:20 PM
Nanosegregated Catalysts for Polymer Electrolyte Membrane Fuel Cells: Theoretical Modeling: Guofeng Wang1; Zhiyao Duan1; 1Univeristy of Pittsburgh
Platinum (Pt) alloy nanoparticles are the most efficient catalysts to promote the electrochemical reactions in polymer electrolyte membrane fuel cells. The performance of these Pt alloy electrocatatalysts are determined by the arrangement of different elements in their surface regions. In this work, we employed an atomistic Monte Carlo simulation method to model the surface segregation processes and predict the equilibrium structure and surface composition of various nanosegregated Pt alloy nanoparticles. Specifically, we have examined our computational approach for several Pt bimetallic alloys that represent different fashions of Pt segregation to the surfaces: Pt-Ni (strong and oscillatory surface segregation), Pt-Re (strong and monotonic surface segregation), Pt-Mo (weak and monotonic surface segregation), Pt-Ti (surface segregation sensitive to bulk composition), and Pt-Fe (surface segregation in ordered alloys). Furthermore, we used density functional theory calculation method to investigate how the surface segregation affects the kinetics of chemical reactions on the nanosegregated Pt alloy catalysts.
4:40 PM
Atomically Precise, Ligand-Stabilized Au25 Clusters for High Efficiency Electrochemical CO2 Reduction: Douglas Kauffman1; Dominic Alfonso1; Christopher Matranga1; Huifeng Qian2; Rongchao Jin2; 1National Energy Technolgoy Laboratory; 2Carnegie Mellon University
Atomically precise Au25 clusters are exciting catalyst candidates for reactions like CO2 reduction because they bridge the size-gap between molecules and nanoparticles, their surface structure is precisely known, and they possess an inherent negative charge. We found the Au25 electrocatalyst was capable of promoting the CO2 reduction reaction within 90 mV of the formal potential (thermodynamic limit). This represents a ~300 mV improvement over larger Au nanoparticles and bulk Au. We found peak CO2 conversion occurred at 1V vs. the reversible hydrogen electrode (pH = 7) with ~100% efficiency and a rate ~7-700 times higher than larger Au catalysts and ~10-100 times higher than current state-of-the-art processes. We also used optical spectroscopy, non-aqueous electrochemistry and density functional theory (DFT) modeling to study CO2 adsorption at the Au25 surface. Results indicate CO2 physisorption induces an electronic interaction wherein charge is reversibly redistribute within the Au25 cluster.