Abstract
Ti-V-based body-centered cubic (BCC) alloys have potential for large-scale hydrogen storage if expensive vanadium is substituted with much cheaper Fe-containing ferrovanadium. Use of ferrovanadium reduces the alloys’ hydrogen storage capacity. This is puzzling since the amount of Fe is low and hydrogen atoms are accommodated in interstitial sites which are partly coordinated by Fe in many intermetallic compounds. The present work is aimed at finding a structural explanation for Fe-induced capacity loss in Ti-V alloys. Since such alloys and their hydrides are highly disordered without long-range occupational order of the different metal species, it was necessary to employ a technique which is sensitive to local structure. Neutron total scattering coupled with reverse Monte Carlo modelling was thus employed to elucidate short-range atomic correlations in Ti0.63V0.27Fe0.10D1.73 from the pair distribution function. It was found that Fe atoms form clusters and that the majority of the vacant interstitial sites are within these clusters. These clusters take the same face-centered cubic structure as the Ti-V matrix in the deuteride and thus they are not simply unreacted Fe which has a BCC structure. The presence of Fe clusters is confirmed by transmission electron microscopy. Density functional theory calculations indicate that the clustering is driven by thermodynamics.
Highlights
The potentially catastrophic consequences of our reliance on fossil fuels have led to a world-wide effort to increase the share of renewables in the global energy mix
Deuterated alloy was on the other hand easy to crush to a fine powder in a mortar
The clusters are observed by Transmission electron electron microscopy microscopy (TEM)/EDS
Summary
The potentially catastrophic consequences of our reliance on fossil fuels have led to a world-wide effort to increase the share of renewables in the global energy mix. Most renewable energy sources, such as wind and solar power, are highly intermittent and should be coupled with energy storage devices that can save excess energy for use when the sun is not shining and the wind does not blow. A viable alternative is to use excess energy to produce hydrogen from water by electrolysis. The hydrogen can later be fed to a fuel cell to produce electricity on demand. Gaseous hydrogen has a very low density even at high pressure, leading to low volumetric energy density for hydrogen gas-based energy storage systems. Gas compression itself is Energies 2020, 13, 1947; doi:10.3390/en13081947 www.mdpi.com/journal/energies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
