Abstract
We are now dealing with several worldwide issues, including the rapid depletion of fossil fuels,
pollution, and global warming. Therefore, secondary energy sources to replace coal, petroleum,
and natural gas are critical for long-term development. Because of its numerous sources, purity,
minimal carbon emissions, flexibility, and excellent efficiency, Hydrogen (H2) energy is the most
promising energy for the future. The global inclination to accept the so-called "Hydrogen
Economy" has grown as the demand for clean and efficient energy is expanding. The Hydrogen
economy's major setback is purification and separation from impurities like CO2, N, HCL, etc. The
current Hydrogen production has 99.97% purity. However, the current materials used for
Hydrogen Purification are palladium and palladium alloys are very scary and highly expensive,
which has brought a major setback for large-scale industrial production.
Pure vanadium also shows higher permeability than Palladium, but due to high solubility in
Hydrogen, it exhibits Hydrogen embrittlement at a temperature above 1500C, which contribute to
its setback. However, adding Nickle power to vanadium to form vanadium-nickel (V-Ni) alloys
will subdue Hydrogen embrittlement. The inter-metallic diffusion that used to occur in previous
research, mainly caused by fabrication methods like electroless plating, sol-gel, arc melting etc.,
will be resolved using an innovative technique called Atomic layer deposition (ALD).
This study developed a new metallic composite membrane by dopping zirconium atoms into
Vanadium-Nickel alloys and investigating its behaviour when exposed to hydrogen during
purification. Numerical modelling and simulation of hydrogen purification were performed at the
atomistic level from the first principle method using density functional theory(DFT) implemented
in the Vienna Abi Initio Simulation Package(VASP) software package.
Vanadium-Nickel based alloys are considered to be among the most promising hydrogen
separation membranes due to their high hydrogen permeability which is a great interest of this
dissertation, and the dissolution and diffusion of hydrogen in Vanadium-Nickel-Zcronium(V-Ni-
Zr) alloy composite membrane was investigated. The adsorption energy was calculated as -
3.6718eV and -3.0233eV for solution energy without Zero-Point Energy(ZPE) and with Zero-
Point Energy(ZPE), respectively. Therefore, the addition of alloying elements like Nickel and
Zirconium elements with small atomic sizes reduces the solubility of hydrogen in pure vanadium
and enhances its resistance to hydrogen embrittlement. For hydrogen diffusion, V-Ni-Zr composite membrane can be a good candidate because its shows higher barrier energy of 0.2eV and hydrogen
diffusion coefficient of 0.699 x 10-4cm2s-1 than other ternary alloys of Vanadium-Nickel based
alloys that were reported in the literature. The mechanical properties and elastic properties show
that this composite membrane is mechanically stable. Its high value of Young's modulus shows
that it has higher stiffness for deformation.
Secondly, the selectivity and permeability of hydrogen over other mixtures of gases like CO, CO2,
CH4, N2 and H2S on the surface of the V-Ni-Zr composite membrane were investigated. The
adsorption properties of the gas mixture were calculated, and the predicted result shows that both
CH4 and CO did not adsorb through the surface of the V-Ni-Zr composite membrane. The
electronic charged density also supports it by showing the bonding properties between the
membrane and the mixture of each gas.
The results demonstrate an excellent selectivity of H2 over other mixtures of gases(CO, CO2, CH4,
N2, and H2S) at varying temperatures based on the predicted permeance of H2. This work
effectively evaluates the permeability and selectivity of metal alloy membranes for gas separation.
This study will enormously contribute towards developing novel composite membranes for
hydrogen purification for the sustainability of Hydrogen Economics, which can be further tested
experimentally and used in a Fuel cell for hydrogen generation. The Author believed that the
outcome of this research would provide a basic guideline for experiments and contribute to the
field of Engineering.