Eletrocatalisadores baseados em Pd/C, PdCu/C, PdNi/C e PdAg/C foram produzidos pelo método de micro-ondas para serem utilizados como cátodo na célula a combustível alcalina na ausência e presença de álcool. Este método se mostrou bastante efetivo para a produção dos materiais, uma vez que as partículas apresentaram boa dispersão no suporte de carbono e produziram eletrocatalisadores com tamanho de partícula em torno de 3,5 nm, de acordo com as análises de DRX e MET. A partir das voltametrias cíclicas observa-se que para os eletrocatalisadores de PdCu/C e PdNi/C quanto maior a quantidade de Cu ou Ni, respectivamente, maior a área ativa do material estudado. Análises de disco anel rotatório foram realizadas nos eletrocatalisadores demonstrando que, independente da composição estudada, a quantidade produzida de peróxido foi de no máximo 4%. Estes dados corroboram com as inclinação das retas nas análises de Koutecky-Levich, uma vez que em ambos os casos a RRO ocorre via 4 elétrons. Análises de estabilidade dos materiais demonstraram que todos eles mantiveram ou melhoraram seu desempenho diante da RRO, quando se compara os dados obtidos antes e depois de 1000 ciclos voltamétricos. Testes de tolerância ao metanol e etanol foram realizados em meia célula com todas as composições de eletrocatalisadores produzidos. Na presença tanto de metanol quanto de etanol as composições atômica de 50:50, para todos os materiais estudados, foram as que demonstraram menor influência da presença do álcool durante a varredura linear da RRO. Nas medidas realizadas em célula unitária, com relação à tolerância ao metanol durante a RRO, o eletrocatalisador que demonstrou melhor desempenho foi o PdAg/C 70:30 enquanto que na presença de etanol o eletrocatalisador que demonstrou melhor desempenho foi o PdNi/C 70:30. / Pd/C, PdCu/C, PdNi/C and PdAg/C electrocatalysts were produced by microwave method to be used as cathode in alkaline fuel cell in the absence and presence of alcohol. This method showed to be effective for the materials production, the particles exhibited good dispersion in carbon support and it produced electrocatalysts with a particle size of about 3.5 nm, according to XRD and TEM analysis. In cyclic voltammetry is observed that PdCu/C and PdNi/C electrocatalysts has higher active area with higher amount of Cu and Ni, respectively. Rotating ring disk analysis in the electrocatalysts showed that the amount of peroxide produced was at most 4%. This data is similar to Koutecky-Levich analysis, once for both the ORR occurs via 4 electrons. Materials stability analysis showed that they kept or improve performance in ORR, comparing the data before and after 1000 voltammetric cycles. Tolerance tests in methanol and ethanol were performed in a half cell in all electrocatalysts compositions. In presence of methanol and ethanol the compositions 50:50, to all materials studied, showed less influence in the presence of alcohol in ORR linear scan. In alkaline fuel cell PdAg/C 70:30 showed better performance for ORR in presence of methanol and PdNi/C 70:30 showed better performance for ORR in ethanol presence.

The first part of this dissertation highlights the contents of the electrochemical characterization of Cu and its electroplating on Ru-based substrates. The growth of Ru native oxide does diminish the efficiency of Cu plating on Ru surface. However, the electrochemical formed irreversible Ru hydrate dioxide (RuOxHy) shows better coverage of Cu UPD. The conductive Ru oxides are directly plateable liner materials as potential diffusion barriers for the IC fabrication. The part II of this dissertation demonstrates the development of a new rapid corrosion screening methodology for effective characterization Cu bimetallic corrosion in CMP and post-CMP environments. The corrosion inhibitors and antioxidants were studied in this dissertation. In part III, a new SEC methodology was developed to study the ORR catalysts. This novel SEC cell can offer cheap, rapid optical screening results, which helps the efficient development of a better ORR catalyst. Also, the SEC method is capable for identifying the poisoning of electrocatalysts. Our data show that the RuOxHy processes several outstanding properties of ORR such as high tolerance of sulfation, high kinetic current limitation and low percentage of hydrogen peroxide.

Este trabajo de Tesis Doctoral se ha centrado en comprender el comportamiento de electrocatalizadores basados en materiales carbonosos para la reacción de reducción de oxígeno. Con el fin de profundizar en el conocimiento de la naturaleza de los sitios activos de catalizadores basados en materiales carbonosos para esta reacción, se han seleccionado o preparado muestras con diferentes composiciones, texturas porosas y estructuras. De estos resultados se han conseguido importantes avances en el conocimiento del papel que los sitios activos de catalizadores basados en materiales carbonosos desempeñan en dicha reacción. Estos conocimientos y los materiales derivados pueden utilizarse en el desarrollo de cátodos para pilas de combustible en medio alcalino. / Heiwa Nakajima Foundation

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Developing highly active and durable oxygen reduction reaction (ORR) catalysts is crucial to reduce the cost of polymer electrolyte fuel cells (PEFCs). To meet those requirements, unsupported Pt-Cu alloy nanochains (aerogels) were synthesized by a simple co-reduction route in aqueous solution and their structure was characterized by X-ray absorption spectroscopy and STEM-EDX. These catalysts exceeded the ORR activity of commercial Pt/C catalysts by more than 100 % in RDE experiments and met the US DOE targets, thereby qualifying as very promising materials. The behavior of Pt-Cu aerogels under PEFC operation conditions was mimicked by acid washing experiments which showed that the Cu content in the alloy phase and ORR activity decrease through this step. Comparing composition, structure and ORR activity for various specimens, the Cu content in the alloy phase was identified as the main descriptor of ORR activity. An almost linear correlation was found between those two parameters and complemented by supporting data from the literature.

This thesis describes the fabrication of an induction heating apparatus and its use to directly heat small platinum and gold electrodes in electrolyte solution. The heating characteristics of the electrodes were studied via the entropic shift of redox potential with temperature and change in Faradaic current. Temperature pulse voltammetry (TPV) and cyclic voltammetry were used for temperature calibration under various heating conditions. The maximum temperature reached at a 0.25 mm diam platinum electrode surface in solution was 84 degrees C. At heated electrodes an increase in current was found to be due to convection and diffusion. TPV was performed with inductively heated gold (0.5 mm diam) and platinum electrodes, which gave complete current-potential-temperature information. Induction heated Pt electrodes were employed to investigate the kinetics and mass transfer process of oxygen reduction reaction (ORR) in acidic and alkaline media.

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No description available.

abstract: This work aimed to characterize and optimize the variables that influence the Gas Diffusion Layer (GDL) preparation using design of experiment (DOE) approach. In the process of GDL preparation, the quantity of carbon support and Teflon were found to have significant influence on the Proton Exchange Membrane Fuel Cell (PEMFC). Characterization methods like surface roughness, wetting characteristics, microstructure surface morphology, pore size distribution, thermal conductivity of GDLs were examined using laser interferometer, Goniometer, SEM, porosimetry and thermal conductivity analyzer respectively. The GDLs were evaluated in single cell PEMFC under various operating conditions of temperature and relative humidity (RH) using air as oxidant. Electrodes were prepared with different PUREBLACK® and poly-tetrafluoroethylene (PTFE) content in the diffusion layer and maintaining catalytic layer with a Pt-loading (0.4 mg cm-2). In the study, a 73.16 wt.% level of PB and 34 wt.% level of PTFE was the optimal compositions for GDL at 70 °C for 70% RH under air atmosphere. For most electrochemical processes the oxygen reduction is very vita reaction. Pt loading in the electrocatalyst contributes towards the total cost of electrochemical devices. Reducing the Pt loading in electrocatalysts with high efficiency is important for the development of fuel cell technologies. To this end, this thesis work reports the approach to lower down the Pt loading in electrocatalyst based on N-doped carbon nanotubes derived from Zeolitic Imidazolate Frameworks (ZIF-67) for oxygen reduction. This electrocatalyst perform with higher electrocatalytic activity and stability for oxygen reduction in fuel cell testing. The electrochemical properties are mainly due to the synergistic effect from N-doped carbon nanotubes derived from ZIF and Pt loading. The strategy with low Pt loading forecasts in emerging highly active and less expensive electrocatalysts in electrochemical energy devices. This thesis focuses on: (i) methods to obtain greater power density by optimizing content of wet-proofing agent (PTFE) and fine-grained, hydrophobic, microporous layer (MPL); (ii) modeling full factorial analysis of PEMFC for evaluation with experimental results and predicting further improvements in performance; (iii) methods to obtain high levels of performance with low Pt loading electrodes based on N-doped carbon nanotubes derived from ZIF-67 and Pt. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

During the past two decades, one of the positive developments in academia has been the emergence of a sizable literature pertaining to ecological education-the theory and practice of preparing children and adults alike for ecologically responsible citizenship. Gregory A. Smith, David W. Orr, and C. A. Bowers are three of the more prolific writers in the field. Smith critiques modern primary and secondary education and argues for, and paints a picture of, an alternative "green pedagogy" that seeks to inculcate in students strong community and ecological values. Orr focuses on the social and ethical problems associated with the environmental crisis and the changes that colleges and universities need to make in order to become propagators of, rather than impediments to, a widespread diffusion of ecological literacy. Bowers emphasizes the role that ecologically problematic modern cultural assumptions play in blinkering the ecological vision of most educational theorists and in preventing the flowering of an eco-justice pedagogy. Each writer seeks the transformation of both education and culture with a view toward realizing ecological sustainability, strong communities, social justice, and moral edification. They neglect or ignore some important subjects, including animal welfare ethics, politics, and corporate influence on governments.