Synthesis and characterization of lithium nickel phosphate nanocrystals via a microemulsion method as a new class of electrocatalyst for oxygen reduction

This thesis examines the electrocatalytic properties shown by lithium nickel phosphate nanoparticles for the oxygen reduction reaction (ORR), an important cathode reaction in fuel cells. The main drawback to the continued development of fuel cells is the relatively slow rate of the ORR compared with a reaction at the anode of a fuel cell. Electrocatalysts are necessary to increase the rate of oxygen reduction and allow more power to be generated at higher efficiencies. Inspired by ideas from chemical catalysis, lithium nickel phosphate nanoparticles were synthesized to determine the possibility of its use as an electrocatalyst for oxygen reduction.;Lithium nickel phosphate nanomaterials were synthesized using a microemulsion approach, with a novel washing and drying technique. The resulting powders were characterized using XRD and FESEM to determine composition and particle size, along with particle uniformity throughout the sample. It was determined that the microemulsion method could be used to predictably tailor the size, shape, and crystalline nature of the product by changing various variables within the synthesis method. The resulting products were studied electrochemically using the rotating ring disk electrode (RRDE) to observe the mechanism of oxygen reduction on the LiNiPO4 surface, along with the effect that the particle size had on the electrocatalysis of the oxygen reduction reaction.;The mechanism of oxygen reduction on LiNiPO4 is via the two electron peroxide pathway, followed by another two electron peroxide dissociation reaction to produce water. The electrocatalysis of oxygen using LiNiPO 4 catalyzes the two electron reaction of oxygen to form peroxide. RRDE results showed that larger particle sizes created larger amounts of electrocatalytic activity. At the largest particle sizes, it was found that peroxide would also be preferentially dissociated at the electrocatalyst surface, producing the full four-electron pathway and increasing the number of electrons transferred per oxygen molecule adsorbed.