Sviluppo di sistemi di produzione elettrolitica di idrogeno senza ricorso a catalizzatori del gruppo del platino

The work presented herein takes into account the fundamental and technological issues associated to the realization of water electrolysis in an alkaline environment, without the use of devices with proton exchange membrane (PEM). Due to the high cost and limited availability of platinum group metals (PGM), used as catalysts in PEM electrolysers, these devices have little chance of being employed in the production of hydrogen on a large scale. Owing to recent advances in the development of non-PGM catalysts, this limitation can be overcome by using non-PEM alkaline electrolysis systems. The experimental results collected in this thesis demonstrate how an alkaline electrolyser, with performances comparable with those of PEM electrolysers, can be achieved without resorting to PGM and high stability and durability catalysts. The studies on the advantages and limitations of such electrolysers, with different architectures, show how a judicious application of differential pressure in a system with electrolyte recirculation helps to reduce the limits of mass transport and increases the system efficiency and power density.