Synthesis Of Pt, Pd Noble Nanoparticles And Their Electrocatalytic Activity For Formic Acid Oxidation

Energy shortage will be a serious problem that human has to face in the future.Fuel cell as electricity generated equipment can convert fuel’s chemical energy toelectricity power directly by electrochemical method, and is hopeful to become the best,clean and high efficient electricity generating technology. As one of the most studiedfuel cells, direct formic acid fuel cells (DFAFCs) show wide and promising applicationsin portable equipment, electric car and field power etc., due to the low-pollution,abundant sources, high energy efficiency, ease of storage and transportation. However,the low electrochemical activity and high cost of the electrocatalysts are still the keyissues hindering the commercial application of DFAFCs. Therefore, it is of criticalimportance to improve the catalytic activity of the electrocatalysts and decrease theloading mass of noble metals.In this thesis, electrocatalysts were deposited on glass carbon electrode (GCE),indium tin oxidation (ITO) glass, Pt and Au electrodes potentiostatically orpotentiodynamically. The morphology and composition of the catalysts werecharacterized by SEM, EDX, and XRD techniques. The catalytic activities ofas-obtained catalysts towards formic acid electrooxidation were systematically studied.The main work of this thesis is as follows:(1) Pt-Au bimetallic catalysts have been fabricated on GCE potentiostatically.As-formed catalysts were characterized by SEM, EDX and electrochemical methods.SEM images reveal that the catalysts show near-spherical morphology with roughsurfaces. CV and chronoamperometry results indicate that the introduction of Au intobimetallic catalysts is beneficial to the electro-catalytic oxidation of formic acid and theanti-poisoning ability of Pt. The formic acid oxidation mechanism on these bimetalliccatalysts has been elucidated using an electrochemical impedance spectroscopytechnique. Moreover, the effect of Au loading in the bimetallic catalyst on formic acid oxidation has been studied. An optimal catalyst of Pt1Au1.803with the highest catalyticactivity for formic acid electrooxidation was finally obtained.(2) Pt-modified Au, another bimetallic catalyst different from the above one, hasbeen designed and electrochemically fabricated on GCE in this part. The obtainedcatalyst is featured with novel layered structure and ultralow Pt loading. SEMcharacterization signifies that the catalyst grows in a Stranski-Krastanov mode, resultingin a nearly ideal layer structure, with Au as the inner layer and Pt as the outer layer. Thecatalytic activity of as-formed Pt/Au/GC towards electrooxidation of formic acid wasstudied, and parallel studies of other catalysts modified electrodes (i.e. Pt/GC, Pt/Au,and Pt/Pt) have also been conducted. As a result, the electrocatalytic activity of Ptdepends significantly on the intrinsic properties of the substrates, and Pt/Au/GCelectrode with freshly prepared Au shows much higher catalytic activity for formic acidoxidation compared with Pt/GC, Pt/Au, and Pt/Pt electrodes. Additionally, the measuredelectrochemical impedance spectra indicate that the charge-transfer resistance forformic acid electrooxidation on Pt/Au/GC is smaller than that on other Pt modifiedelectrodes.(3) Pine needle-like Pd micro/nano-leaves have been directly electrodeposited onITO glass substrate by a facile and template-free electrochemical method. Themorphology and composition of obtained Pd catalyst were characterized by SEM andXRD. The catalytic activity of the catalyst towards formic acid electrooxidation hasbeen investigated. Compared to conventional Pd nanoparticles, as-prepared Pdmicro/nano-leaves exhibit superior electrocatalytic activity for formic acid oxidation.