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Authors
Abstract(s)
The need for alternative fuels has been increasing since the latest decades due to climate change. Climate
change is caused by the release of greenhouse gases, mainly CO2 and CH4, which has increased
dramatically with the industrialisation of developing countries. Species like NH3 can be used as a carrier
to produce via its electrocatalytic conversion, H2 as an alternative carbon-free fuel, offering several
advantages when compared with the water splitting process. Advantages such as, a 95% lower standard
redox E and a 50% higher hydrogen quantity per molecule. Metal-organic frameworks structures that
have high crystallinity and permanent porosity constituted by an inorganic centre and organic ligand.
These structures show promising results as catalysts due to their properties and the presence of active
sites. The use of these structures as electrocatalysts require their immobilisation on a conductive surface,
as they are obtained in powder form using the most common method – solvothermal synthesis. There
are two different electrochemical methods for the formation of metal-organic framework films, a direct
method, consisting of the formation of the metal-organic framework directly on the surface of the
conductive substrate and an indirect method, which focuses on immobilising these materials in a powder
form post-synthesis. This work focuses on the synthesis, immobilisation, and electrochemical studies of
some of these materials as well as their application for the electroconversion of ammonia. The films
were formed using the cathodic deposition as the direct method and the electrophoretic deposition as the
indirect method. The obtained metal-organic framework powders and films were characterised using Xrays diffraction, Fourier Transform infrared spectroscopy and scanning-electron microscopy. The
electrochemical studies were made using cyclic voltammetry and the conversion of NH3 was
investigated using controlled potential electrolysis experiments and its products were quantified using
gas chromatography with a thermal conductivity detector.
Description
Tese de mestrado, Química (Química), 2023, Universidade de Lisboa, Faculdade de Ciências
Keywords
Estruturas metalo-orgânicas deposição eletroquímica filmes conversão de amoníaco hidrogénio Teses de mestrado - 2023