Preparation And Catalytic Performance Of Electro-catalysts For Oxygen Reduction

Fuel cell is a clean, low-cost, high-efficient energy conversion device that converts thechemical energy into electricity through a chemical reaction with oxygen. Oxygen reductionreaction (ORR) is important and widely studied in fuel cells, Recently, the catalyst of carbonblack supporting platinum-based nanoparticles are widely used for ORR. However, it iseasily poisoned by intermediate product CO and the high cost limits its application incommercial field. Thus, investigation focuses on reducing Pt-based electrode in fuel cells ordeveloping new ORR catalysts is an important topic. According to the literatures, bothgraphene-Pt NP hybrid films and metalloporphyrin-Au NP hybrid films show a superiorcatalytic activity for oxygen reduction and resist to CO poisoning. Base on these papers, weprepare electro-catalysts for oxygen reduction with low cost and high efficiency. In this work,we report on the direct synthesis of graphene-Pt nanocomposite films by using the directelectrochemically deposition method and the synthesis of metalloporphyrin-Au NP hybridfilms by using layer by layer method. The electro-catalytic activity toward oxygen reductionof the above two catalysts is studied. The main contents in this dissertation are summarizedas follows:(1) GN/Pt nanocomposites were fabricated by a simple, friendly, environmentally,direct electrochemical deposition approach which can control the thickness of the film bydifferent deposition time and cycles. The structure of the GN/Pt nanocomposites wascharacterized through SEM, Raman and XPS. The electrocatalytic performances were testedby cyclic voltammetric and liner sweep voltammetric. The results show that the Pt NPs andreduced graphene oxide have been successfully modified to the electrode. Theelectrochemical tests show that the resulting hybrid material GN/Pt shows goodelectro-catalytic activity for oxygen reduction.(2)[AuNP/CoTMPyP]nwere fabricated by electrostatic layer-by-layer (LBL)self-assembly technique. A three dimensional nanostructured film composed of positivelycharged CoTMPyP and negatively charged poly (acrylic acid)-stabilized AuNPs can beformed onto various substrates, including4-aminobenzoic acid modified glassy carbonelectrode,11-mercaptotroponic acid modified gold film, and quartz plate with negativelycharged surface. The regular growth of hybrid films is investigated by UV-vis spectroscopy, surface plasma resonance, and impedance spectroscopy. The prepared multilayer filmspossess flexible electro-catalytic activity toward O2reduction reaction.