Ir-based nanoparticles for catalytic hydrogen generation using chemical hydrogen storage compounds

The objective of this thesis is to present and evaluate hydrous hydrazine as a suitable liquid storage compound for the production of hydrogen that can be utilised for hydrogen fuel cells. Catalytic decomposition of hydrous hydrazine at mild conditions is considered for application for hydrogen generation in portable devices, focusing on the (I) productivity, (II) reusability of the catalysts and the yield of hydrogen and (III) avoiding the production of ammonia which is harmful to the fuel cell membrane. Ir-based nanoparticles were synthesised and deposited on a range of supports and different preparation methods were used to tune their structural and catalytic properties. Moreover, computational calculations were used to elucidate the mechanism of reaction and the interaction of the catalytic surface with the hydrazine and intermediates. The catalytic performance of a synthesised Ir/CeO2 as reference material is presented in order to optimise the reaction conditions for identifying the kinetic regime of the studied reaction. Characterisation techniques and computational calculations are used to provide possible reaction pathways for tuning the yield of the reaction toward hydrogen production. After the determination of the optimal reaction parameters the preparation methods of supported monometallic Ir nanoparticles were modified in order (I) to tune the catalytic properties of active metal, (II) explore possible metal-support interactions by using different metal oxides as support and finally (III) optimising the yield of the reaction towards hydrogen. ATR-IR studies were carried out in order to identify adsorbed species on the surface of the desired model catalyst in specific chosen reaction conditions and validate the possible mechanisms of the reaction. Once Ir-based catalysts were optimised Ni-based catalysts were subsequently investigated to perform hydrous hydrazine catalytic decomposition with higher yield toward molecular hydrogen. From the knowledge obtained by the catalytic and characterisation studies of monometallic Ir and Ni catalysts bimetallic Ir-Ni catalysts were synthesised and characterised in order to combine the higher selectivity and higher activity of the two monometallic catalysts. Characterisations were performed to investigate and elucidate the properties of the bimetallic materials synthesised. Finally, the main conclusions of the results are reported and a set of options to continue this research is presented