Nanocrystalline Porous Hydrogen Storage Based on Vanadium and Titanium Nitrides

A Goncharov,E Lyubchenko,A Guglya,V Vlasov,E Solopikhina,A Kalchenko

doi:10.1155/2017/4106067

Abstract

This review summarizes results of our study of the application of ion-beam assisted deposition (IBAD) technology for creation of nanoporous thin-film structures that can absorb more than 6 wt.% of hydrogen. Data of mathematical modeling are presented highlighting the structure formation and component creation of the films during their deposition at the time of simultaneous bombardment by mixed beam of nitrogen and helium ions with energy of 30 keV. Results of high-resolution transmission electron microscopy revealed that VNxfilms consist of 150–200 nm particles, boundaries of which contain nanopores of 10–15 nm diameters. Particles themselves consist of randomly oriented 10–20 nm nanograins. Grain boundaries also contain nanopores (3–8 nm). Examination of the absorption characteristics of VNx, TiNx, and(V,Ti)Nxfilms showed that the amount of absorbed hydrogen depends very little on the chemical composition of films, but it is determined by the structure pore. The amount of absorbed hydrogen at 0.3 MPa and 20°C is 6-7 wt.%, whereas the bulk of hydrogen is accumulated in the grain boundaries and pores. Films begin to release hydrogen even at 50°C, and it is desorbed completely at the temperature range of 50–250°C. It was found that the electrical resistance of films during the hydrogen desorption increases 104times.

Highlights

Vanadium and titanium hydrides are deemed to be promising as solid state hydrogen storage
The objective of this review is to justify the principles of efficient solid state hydrogen storage formation and to show, in the case of titanium and vanadium, how to create structures with the desired gravimetric, thermodynamic, and kinetic characteristics
Using SPURT program as described previously in [24], we performed a mathematical simulation of the defect formation (Figure 1(a)) and ion implantation of nitrogen and helium (Figure 1(b)) in deposited vanadium films

Summary

Introduction

Vanadium and titanium hydrides are deemed to be promising as solid state hydrogen storage. The total mass of stored hydrogen in VH2 approaches value of 2.1 wt.%. The amount of absorbed hydrogen atoms comes to be 11.2 in VH2 and 9.1 in TiH2 (at/cm3, ×1022). Amounts are essentially higher than, for example, in popular MgH2 hydride (2.5 at/cm3, ×1022) [1]. V-H system includes the following phases: α- solid solution; β-(VH0.45–VH0.95) with body-centered tetragonal lattice (bct), and γ-VH2 with fcc-lattice (it is unstable at the atmospheric pressure). The β + γ phase mixture is in the VH1.0–VH2.0 concentration range

Objectives

Results

Conclusion