Advancing Palladium-Based Nanostructures for Catalysis : From Nanoparticles to Multifunctional Nanoarchitectures

The development of nanoscale materials is essential across various fields, including catalysis. The intrinsic properties of well-defined nanometre-sized catalysts directly influence their catalytic performance. This thesis investigates the design, fabrication and optimisation of palladium (Pd)-based nanostructures as potential nanocatalysts through a multidisciplinary approach combining state-of-the-art fabrication and characterisation methods. High-purity Pd nanoparticles, fabricated via a chemical-free spark ablation method, serve as the core building blocks, offering precise control over size and composition, essential for tuneable catalytic properties. The first study, addressed in Paper I, focuses on enhancing spark discharge generator (SDG) efficiency through COMSOL simulations and experimental studies, paving the way for higher-throughput catalytic nanoparticle production. The nanoparticle tunability extended to Pd-based alloys was investigated in Paper II, exploring the synthesis of Pd-Ga alloy nanoparticles via a novel combination of spark ablation and in-flight metal-organic precursor decomposition, which demonstrates the ability to fine-tune catalytic properties by controlling composition and processing conditions. Pd nanoparticles are further integrated with gallium phosphide (GaP) nanowires to create innovative hybrid nanocatalysts, as detailed in Paper III. The design and surface engineering of these nanostructures reveal the critical role of their morphology in catalytic performance, particularly in hydrogenation reactions. The final study, in Paper IV, examines the growth of branched GaP nanowires using Pd nanoparticles as seeds, achieving three-dimensional structures with enhanced surface area and attractive for catalytic applications. This research contributes to the development of solid-state nanocatalysts by leveraging the precise generation of Pd nanoparticles and alloy materials and their integration with semiconductor-based supports. The findings highlight the potential for these materials as nanocatalysts.