The development of new materials has always been strictly related to the rise of new technologies and progressively efficient systems. However, cutting-edge materials might not be enough to ensure the effectiveness of a given product if the design guidelines used do not favor the specific advantages of this material. Polymeric composites are known for their excellent mechanical properties, but current manufacturing techniques and the relatively narrow expertise in the field amongst engineers impose the challenge to provide the most suitable designs to certain applications. Bio-inspired designs, supported by thousands of years of evolution of nature, have shown to be extremely profitable tools for the design of optimized yet structurally complex shapes in which the tailoring aspect of polymeric composites perfectly fit. Bearing in mind the current but old-fashioned designs of auto-parts and vehicles built with metals with little or no topological optimization, the present work addresses how biomimicry is being applied in the mobility industry nowadays to provide lightweight structures and efficient designs. A general overview of biomimicry is made regarding vehicles, approaching how the use of composite materials has already contributed to successful cases.

The effect of Sn loading (5-30 mol %) on Pt catalysts supported on reduced graphene oxide was investigated for ethanol electro-oxidation in acidic medium. Reduced graphene oxide was synthesized via graphite oxidation-exfoliation process in liquid phase and chemical reduction. Pt and Pt x Sn y catalysts were deposited on reduced graphene oxide by a NaBH 4 impregnation-reduction method. The adopted procedures allowed the synthesis of graphene-like nanosheets where single Sn-doped Pt nanoparticles were impregnated. Pt lattice parameter and micro-strain increased with Sn addition, confirming the formation of a solid solution. Concerning ethanol electro-oxidation, Pt was more active when supported on reduced graphene oxide whereas the introduction of Sn enhanced the catalyst activity, leading to lower ethanol oxidation potentials and higher current densities.

Aos meus pais, Carlos e Ivani Cordeiro, pela liderança e formação, pelo apoio e carinho. Ao meu irmão, Lucas Cordeiro, pelo companheirismo e incentivo. À Dra. Dolores Lazar, pela orientação e pelos conhecimentos transmitidos durante o desenvolvimento deste trabalho. Ao Dr. Almir Neto, pela co-orientação e pelos conhecimentos transmitidos durante o desenvolvimento deste trabalho. Ao Dr. Valter Ussui, pela colaboração e pelas contribuições acadêmicas. Ao Dr. Ricardo Piasentin, pela colaboração e pelas contribuições acadêmicas. Ao Dr. Nelson de Lima, pela colaboração e pelas contribuições acadêmicas.

A simple and low-cost approach for the preparation of wide-gap (E g = 3.43 eV), fine cerium dioxide crystals (CeO 2 , d = 8.1 nm), was developed in order to support Pt nanoparticles as electrocatalysts for ethanol oxidation. Cerium oxide powders were prepared by precipitation from cerium chloride solution in ammonia medium and the influence of calcination temperature was evaluated. Platinum nanoparticles were incorporated by a wet chemical reduction of chloroplatinic acid with sodium borohydrate. Compared to a state-of-the-art Pt/C, the nanocomposite exhibited a much higher mass activity (2.5×) and significant antipoisoning ability. The promotional effect of the CeO 2 nanocrystals was discovered to be affected by heat treatment conditions. Compared to oven-dried samples, calcination allows to (i) an enhanced metal-support interaction between CeO 2 and Pt and (ii) an enhancement of electron transportation to catalyst owing to the shrinkage of CeO 2 bandgap, thereby promoting the oxidation of the strongly adsorbed C x H y. Therefore, the Pt/CeO 2 nanocomposite appears to be a promising electrocatalyst for advanced energy conversion.

Improvements of the catalytic efficiency of nickel–aluminum oxides in reforming reactions for hydrogen production have been achieved by the development of synthesis processes that provide powders with high surface area. The reduction of the crystallization temperature is one of the procedures in this direction. In this work, the effect of solvothermal treatment on coprecipitated gels with 15 wt% nickel content in alumina matrix was evaluated. Powders were obtained by coprecipitation with and without treatment of gels under n-butanol vapor pressure at 150oC. Products were characterized by TG/DTA, X-ray diffraction, specific surface area measurements, scanning electron microscopy and laser beam scattering for granulometric distribution determination. The results showed that calcined powders have high specific surface area (ranging from 170 to 260 m2.g-1) and are composed by gamma alumina and nickel aluminate phases. Aging treatment did not promote hydroxides decomposition under solvothermal conditions, indicating the need of calcination step.