ALTERING THIN FILM HYDRIDE FORMATION PROPERTIES BY PRETREATING SUBSTRATE WITH DC AND PULSED DC INDUCED PLASMA.

Depleting fossil resources and environmental concerns are raising great interest in renewable energy. Unfortunately, renewable energy sources are not equally available throughout time and require energy storage systems to balance supply and demand. Hydrogen as a way of chemical energy storage has a great potential to solve a whole set of energy related problems. A lot of efforts have been made to find a perfect solid state hydrogen storage material which would have high hydrogen storage capacity, proper thermodynamic properties and good cycling stability [1-3]. However, no single material was able to meet the requirement and it became clear that different sorts of material engineering is needed. Traditionally scientist looked for solutions which would improve the bulk properties of the hydride. The biggest step at improving hydrogen storage by changing their bulk properties was achieved by Bogdanavic when he added titanium chloride to sodium alanate [4-5]. Later it was realised that surface properties of the hydrogen storage materials can be equally important. It was shown that for particular materials hydrogenation kinetics can have a limiting step of H₂ dissociation at the surface or diffusion from the surface to the bulk. Various surface catalyst such as Pd, V and Ni significantly increased the hydrogenation kinetics but as with the bulk improvement their effect was not enough to achieve targets set by international energy agencies and industry. During current research it was tested if manipulation of thin film-substrate interaction zone and controlling free surface energy could have significant effects on hydrogenation properties of thin films deposited by magnetron sputtering. For this purpose we have chosen to use a well known and widely described Mg based materials and to deposit them on to the different substrates affected by different plasma treatment. The received experimental data has revealed interesting material behaviour under hydrogenation and provided experimental proof of concept that different surface pretreatment can be used to alter the overall hydrogenation properties of metal hydrides. [ABSTRACT FROM AUTHOR]