This thesis concerns investigations on novel multistage electrochemical deposition of nanostructured systems composed of noble metals platinum, ruthenium, and gold. Various electrochemical synthetic pathways were systematically explored producing multilayered nanoscale electrode systems composed of Pt, Ru, or Au on glassy carbon or crystalline gold used as substrates. Electrochemical pathways involved sequential surface-limited redox-replacement (SLRR) reactions of underpotentially-deposited or overpotentially-deposited copper, potentiostatic dealloying, direct spontaneous deposition of noble metals (without intermediary steps involving redox-replacement templating reactions) as well as sequential codeposition of noble metals (with or without SLRR templating reactions). Fundamental studies were conducted using thermodynamic and kinetic models, in situ electrochemical techniques and ex situ microscopic, spectroscopic, or spectrophotometric techniques employed for probing factors controlling electrode dynamics, electrocatalysis, morphology, bulk and surface compositional properties of the noble metal-based electrode systems. Unique multilayered multimetallic nanoclusters synthesized (with binary active sites of Pt with Ru or Au) exhibited superior electrocatalytic activity towards methanol or formic acid oxidation reactions when benchmarked to equivalent monometallic multilayered Pt. Hydrodynamic electrokinetic studies of the oxygen reduction reaction (ORR) on the multilayered monometallic Pt and bimetallic Rucontaining nanoclusters revealed that the monometallic nanoclusters exhibited direct four-electron ORR whereas electrocatalysis on the bimetallic ones could be tuned to proceed via a two-electron reaction pathway. Electrocatalytic bifunctional reaction mechanisms were especially enhanced by the nanostructured systems investigated. Characterisation of multilayered nanoclusters surface and near-surface metal contents revealed interactions between metal centers, car.

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.

Abstract: Fuel cell, as an alternative green power source for automobiles and portable electronics, has attracted worldwide attention due to its desirable properties such as high energy density and low greenhouse gas emission. Despite great progress in the past decades, several challenges still remain as obstacles for the large-scale commercialization. Among them, the high cost of Pt-based electrode material is considered as a major barrier, while the life span or stability of electrode catalysts is another concern since the electrocatalysts can be easily poisoned during the fuel cell operation. In order to overcome these issues, nanostructured carbon materials, especially carbon nanotubes (CNTs), are studied as catalyst support. In addition, recent research also suggests that the coupling of a second metal element with Pt can effectively protect the electrocatalysts from being poisoned and thus improve their long-term durability. The objective of the present work was to demonstrate an efficient synthetic method for the preparation of CNTs supported binary PtM (M=Ru, Sn) electrocatalysts. In this project, a polymer wrapping technique along with an in-situ polyol reduction strategy was adopted to decorate well-dispersed binary PtM nanoparticles on the surface of modified-CNTs. The unique nanostructures as well as the excellent catalytic activities of the as-prepared nanohybirds were investigated through a diversity of physiochemical and electrochemical characterization techniques. This fabrication method provided a simple and convenient route to assemble Pt-based catalyst on carbon substrates, which is useful for the further development of high-performance fuel cell catalysts.

Nanomaterials have recently garnered significant attention and practical importance for heterogeneous electrocatalysis. This book presents recent developments in the design, synthesis, and characterisation of nanostructured electrocatalytic materials, with a focus on applications to energy and wastewater treatment. Electrocatalytic nanomaterials can enhance process efficiency and sustainability, thus providing innovative solutions for a wide array of areas such as sustainable energy production, conversion, and wastewater treatment. Readers will gain insights into the latest breakthroughs in electrocatalysis and the activity of nanomaterials in energy conversion applications, e.g., fuel cells, hydrogen production, water splitting, and electro/photocatalytic water splitting, as well as for wastewater treatment. The book explores the development of advanced electrocatalysts, particularly hybrid materials.

Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries is a comprehensive book summarizing the recent overview of these new materials developed to date. The book is motivated by research that focuses on the reduction of noble metal content in catalysts to reduce the cost associated to the entire system. Metal oxides gained significant interest in heterogeneous catalysis for basic research and industrial deployment. Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries puts these opportunities and challenges into a broad context, discusses the recent researches and technological advances, and finally provides several pathways and guidelines that could inspire the development of ground-breaking electrochemical devices for energy production or storage. Its primary focus is how materials development is an important approach to produce electricity for key applications such as automotive and industrial. The book is appropriate for those working in academia and R&D in the disciplines of materials science, chemistry, electrochemistry, and engineering. Includes key aspects of materials design to improve the performance of electrode materials for energy conversion and storage device applications Reviews emerging metal oxide materials for hydrogen production, hydrogen oxidation, oxygen reduction and oxygen evolution Discusses metal oxide electrocatalysts for water-splitting, metal-air batteries, electrolyzer, and fuel cell applications

This thesis systematically introduces readers to a new metal-organic framework approach to fabricating nanostructured materials for electrochemical applications. Based on the metal-organic framework (MOF) approach, it also demonstrates the latest ideas on how to create optimal MOF and MOF-derived nanomaterials for electrochemical reactions under controlled conditions. The thesis offers a valuable resource for researchers who want to understand electrochemical reactions at nanoscale and optimize materials from rational design to achieve enhanced electrochemical performance. It also serves as a useful reference guide to fundamental research on advanced electrochemical energy storage materials and the synthesis of nanostructured materials.