Noble Metal Based Nanomaterials in the Application of Direct Alcohol Fuel Cells

Fuel cells are envisaged to be a new generation of power sources which convert chemical energy into electrical energy with, theoretically, both economical and environmental benefit. As a subcategory of polymer electrolyte membrane fuel cells, direct alcohol fuel cells exhibit the most pertinent properties in the application of portable electronic devices. As the most important and the most expensive component in DAFCs, electrocatalysts have attracted considerable academic and industrial attention. One of the en route research on fuel cells aims to develop nanomaterials with better catalytic performance and lower cost. Proceeding towards this goal, this dissertation will be focusing on the study of the cathode and the anode catalysts in DAFCs. Specifically, as anode catalysts, novel palladium based, 1-dimensional, membrane electrodes were fabricated via a facile and versatile electrospinning – electroless plating procedure. Nanofibrous polyamide 6 and titanium dioxide were prepared by electrospinning, serving as the template for the subsequent electroless plating of Pd. The as-prepared, free-standing Pd nanofibers were applied in the electrocatalysis of ethanol oxidation reaction and glycerol oxidation reaction in alkaline medium. Beyond the examination of the activity of the catalysts, the mechanisms of EOR and GOR on Pd in alkaline electrolyte were also studied. In the context of cathode catalysts, platinum-copper alloy nanotubes were synthesized by galvanic replacement reaction using high-quality Cu nanowires as the sacrificial template. This rationally designed electrocatalyst for oxygen reduction reaction inherited the advantage of improved catalytic activity from the incorporation of a second transition metal and ameliorated durability from the 1-dimensional structure, which were verified by rotating disk electrode experiment and accelerated durability test, respectively. In addition, the fabrication of Pt based, free-standing catalyst on a conductive substrate, such as single-walled carbon nanotubes and polyaniline, was also investigated using electrodeposition technique. The applicability of the as-prepared Pt/SWCNTs composite as a free-standing electrocatalyst for ORR was also demonstrated. In summary, the developed methods for the fabrication of free-standing membrane electrodes and rationally designed nanomaterials combining several favorable properties will open up new avenues in the preparation of noble metal based nanomaterials and can be potentially extended to the synthesis of a wider range of electrocatalysts in the application of DAFCs