Proton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) are attractive power sources as they offer high conversion efficiencies with low or no pollution. However, the most commonly used platinum electrocatalyst is expensive and the world supply of Pt is limited. In addition, the slow oxygen reduction and methanol oxidation kinetics as well as the poisoning of the Pt catalyst at the cathode resulting from methanol permeation from the anode through the Nafion membrane to the cathode lead to significant performance loss. Also, the electrocatalyst utilization in the electrodes also needs to be improved to reduce the overall cost of the electrocatalysts and improve the fuel cell performance. This dissertation explores nanostructured Pt alloys with lower cost and higher catalytic activity than Pt for oxygen reduction in PEMFC to understand the effect of synthesis and structure on the catalytic activity, methanol tolerant Pt/TiOx nanocomposites for oxygen reduction in DMFC, nanostructured Pt-Ru alloys for methanol oxidation in DMFC, and improvement in the utilization of Pt by optimizing the membrane-electrode assembly (MEA) fabrication. From a systematic investigation of a series of Pt-M alloys (M = Fe, Co, Ni, and Cu), the catalytic activity of Pt-M alloys is correlated with the extent of atomic ordering. More ordered Pt alloys exhibit higher catalytic activity than disordered Pt alloys. The higher activity of the ordered Pt alloys is found to relate to various factors including the Pt-Pt distance, Pt: 5d orbital vacancy, {100} planar density and surface atomic configuration. The catalytic activity of the Pt alloys is also influenced by the synthesis method. Low temperature solution methods usually result in smaller particle size and higher surface area, while high temperature routes result in larger particle size and lower surface area but with a greater extent of alloying. Pt/TiOx/C nanocomposites exhibit higher performance than Pt for oxygen reduction in DMFC. The nanocomposites show higher electrchochemical surface area, lower charge transfer resistance, and higher methanol tolerance than Pt. Pt-Ru alloy synthesized by a reverse microemulsion method exhibits higher catalytic surface area than the commercial Pt-Ru. The higher catalytic activity is attributed to a better control of the particle size, crystallinity, and microstructure. Membrane-electrode assemblies (MEAs) fabricated by a modified thin film method exhibit much higher electrocatalyst utilization efficiency and performance than the conventional MEAs in PEMFC. Power densities of 715 and 610 mW/cm2 are obtained at a Pt loading of, respectively, 0.1 and 0.05 mg/cm2 and 90 oC. The higher electrocatalyst utilization is attributed to the thin catalyst layer and a better continuity of the membrane/catalysts layer interface compared to that in the conventional MEAs.

Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900 °C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation focuses on carbon-supported binary Pt@Cu and ternary PtxPd1-x@Cu "core-shell" nanoparticles synthesized by a novel galvanic displacement of Cu by Pt4+ and Pd2+ at ambient conditions. Structural characterizations suggest that the Pt@Cu nanoparticles have a Pt-Cu alloy layer sandwiched between a copper core and a Pt shell. The electrochemical data clearly point to an enhancement in the activity for ORR for the Pt@Cu "core-shell" nanoparticle electrocatalysts compared to the commercial Pt electrocatalyst, both on per unit mass of Pt and per unit active surface area basis. The increase in activity for ORR is ascribed to electronic modification of the outer Pt shell by the Pt-Cu alloy core. However, incorporation of Pd to obtain PtxPd1-x@Cu deteriorates the activity for ORR.

Proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are two types of low-temperature fuel cells (LTFCs) that operate at temperatures less than 100 °C and are appealing for portable, transportation, and stationary applications. However, commercialization has been hampered by several problems such as cost, efficiency, and durability. New electrocatalysts must be developed that have higher oxygen reduction reaction (ORR) activity, lower precious metal loadings, and improved durability to become commercially viable. This dissertation investigates the development and use of new electrocatalysts for the ORR. Core-shell (shell@core) Pt@Pd[subscript x]Cu[subscript y]/C electrocatalysts, with a range of initial compositions, were synthesized to result in a Pt-rich shell atop a Pd[subscript x]C[subscript y]-rich core. The interaction between core and shell resulted in a delay in the onset of Pt-OH formation, accounting in a 3.5-fold increase in Pt-mass activity compared to Pt/C. The methanol tolerance of the core-shell Pt@PdCu5/C was found to decrease with increasing Pt-shell coverage due to the negative potential shift in the CO oxidation peak. It was discovered that Cu leached out from the cathode has a detrimental effect on membrane-electrode assembly performance. A spray-assisted impregnation method was developed to reduce particle size and increase dispersion on the support in a consistent manner for a Pd88W12/C electrocatalyst. The spray-assisted method resulted in decreased particle size, improved dispersion and more uniform drying compared to a conventional method. These differences resulted in greater performance during operation of a single DMFC and PEMFC. Additionally, Pd88W12/C prepared by spray-assisted impregnation showed DMFC performance similar to Pt/C with similar particle size in the kinetic region while offering improved methanol tolerance. Pd88W12/C also showed comparable maximum power densities and activities normalized by cost in a PEMFC. Lastly, the activation of aluminum as an effective reducing agent for the wet- chemical synthesis of metallic particles by pitting corrosion was explored along with the control of particle morphology. It was found that atomic hydrogen, an intermediate, was the actual reducing agent, and a wide array of metals could be produced. The particle size and dispersion of Pd/C produced using Al was controlled using PVP and FeCl2 as stabilizers. The intermetallic Cu2Sb was similarly prepared with a 20 nm crystallite size for potential use in lithium-ion battery anodes. Lastly, it was found that the shape of Pd produced with Al as a reducing agent could be controlled to prepare 10 nm cubes enclosed by (100) facets with potentially high activity for the ORR.

Nanomaterials for Direct Alcohol Fuel Cells explains nanomaterials and nanocomposites as well as the characterization, manufacturing, and design of alcohol fuel cell applications. The advantages of direct alcohol fuel cells (DAFCs) are significant for reliable and long-lasting portable power sources used in devices such as mobile phones and computers. Even though substantial improvements have been made in DAFC systems over the last decade, more effort is needed to commercialize DAFCs by producing durable, low-cost, and smaller-sized devices. Nanomaterials have an important role to play in achieving this aim. The use of nanotechnology in DAFCs is vital due to their role in the synthesis of nanocatalysts within the manufacturing process. Lately, nanocatalysts containing carbon such as graphene, carbon nanotubes, and carbon nanocoils have also attracted much attention. When compared to traditional materials, carbon-based materials have unique advantages, such as high corrosion resistance, better electrical conductivity, and less catalyst poisoning. This book also covers different aspects of nanocomposites fabrication, including their preparation, design, and characterization techniques for their fuel cell applications. This book is an important reference source for materials scientists, engineers, energy scientists, and electrochemists who are seeking to improve their understanding of how nanomaterials are being used to enhance the efficiency and lower the cost of DAFCs. Shows how nanomaterials are being used for the design and manufacture of DAFCs Explores how nanotechnology is being used to enhance the synthesis and catalysis processes to create the next generation of fuel cells Assesses the major challenges of producing nanomaterial-based DAFCs on an industrial scale

One-dimensional Nanostructures for PEM Fuel Cell Applications provides a review of the progress made in 1D catalysts for applications in polymer electrolyte fuel cells. It highlights the improved understanding of catalytic mechanisms on 1D nanostructures and the new approaches developed for practical applications, also including a critical perspective on current research limits. The book serves as a reference for the design and development of a new generation of catalysts to assist in the realization of successful commercial use that have the potential to decarbonize the domestic heat and transport sectors. In addition, a further commercialization of this technology requires advanced catalysts to address major obstacles faced by the commonly used Pt/C nanoparticles. The unique structure of one-dimensional nanostructures give them advantages to overcome some drawbacks of Pt/C nanoparticles as a new type of excellent catalysts for fuel cell reactions. In recent years, great efforts have been devoted in this area, and much progress has been achieved. Provides a review of 1D catalysts for applications in polymer electrolyte fuel cells Presents an ideal reference for the design and development of a new generation of catalysts to assist in the realization of successful commercial use Highlights the progress made in recent years in this emerging field

Proton exchange membrane (PEM) fuel cells are promising clean energy converting devices with high efficiency and low to zero emissions. Such power sources can be used in transportation, stationary, portable and micro power applications. The key components of these fuel cells are catalysts and catalyst layers. “PEM Fuel Cell Electrocatalysts and Catalyst Layers” provides a comprehensive, in-depth survey of the field, presented by internationally renowned fuel cell scientists. The opening chapters introduce the fundamentals of electrochemical theory and fuel cell catalysis. Later chapters investigate the synthesis, characterization, and activity validation of PEM fuel cell catalysts. Further chapters describe in detail the integration of the electrocatalyst/catalyst layers into the fuel cell, and their performance validation. Researchers and engineers in the fuel cell industry will find this book a valuable resource, as will students of electrochemical engineering and catalyst synthesis.

Metal Nanoclusters in Catalysis and Materials Science: The Issue of Size Control deals with the synthesis of metal nanoclusters along all known methodologies. Physical and chemical properties of metal nanoclusters relevant to their applications in chemical processing and materials science are covered thoroughly. Special attention is given to the role of metal nanoclusters size and shape in catalytic processes and catalytic applications relevant to industrial chemical processing.An excellent text for expanding the knowledge on the chemistry and physics of metal nanoclusters. Divided in two parts; Part I deals with general aspects of the matter and Part II has to be considered a useful handbook dealing with the production of metal nanoclusters, especially from their size-control point of view. * Divided into two parts for ease of reference: general and operational * Separation of synthetic aspects, physical properties and applications* Specific attention is given to the task of metal nanoclusters size-control