Abstract
The desorption behaviors of hydrogen from high entropy alloy TiZrVMoNb hydride surface have been investigated using the density functional theory. The (110) surface has been determined to be the most preferable surface for hydrogen desorption from TiZrVMoNb hydride. Due to the high lattice distortion and heterogeneous chemical environment in HEA hydride, hydrogen desorption from the HEA hydride surface is found to be complex. A comparison of molecular and atomic hydrogen desorption reveals that hydrogen prefers to desorb in atomic states from TiZrVMoNb hydride (110) surface rather than molecular states during the hydrogen desorption process. To combine as H2 molecules, the hydrogen atoms need to overcome attractive interaction from TiZrVMoNb hydride (110) surface. These results suggest that the hydrogen desorption on TiZrVMoNb hydride (110) surface is a chemical process. The presented results provide fundamental insights into the underlying mechanism for hydrogen desorption from HEA hydride surface and may open up more possibilities for designing HEAs with excellent hydrogen desorption ability.
Highlights
Hydrogen, with its quite plentiful amount, cost-effective renewability, high energy density and zero-emission characteristics, has been considered as a potential substitute for fossil fuels in the past several decades [1,2,3,4]
Developing hydrogen storage materials with a low decomposition temperature and pressure, high recyclability, fast kinetics and high hydrogen storage capacity is one of the most crucial difficulties restricting the utilization of hydrogen energy for real applications [5,6,7]
Based on the obtained lattice constant, the (100), (110) and (111) surfaces of high entropy alloys (HEAs) TiZrVMoNb hydrides are modeled by repeated slab models, in which one slab consists of seven atomic layers
Summary
With its quite plentiful amount, cost-effective renewability, high energy density and zero-emission characteristics, has been considered as a potential substitute for fossil fuels in the past several decades [1,2,3,4]. Among the investigations of hydrogen storage of HEAs, efforts have been made to study the desorption properties of HEA hydrides. Montero et al [32] reported that the addition of only 10% Ta into Ti0.325 V0.275 Zr0.125 Nb0.275 decreases the desorption temperature of the hydride phase by around 100 K Despite these experimental studies of dehydrogenation of HEAs hydrides, few theoretical simulations of hydrogen desorption properties of HEAs have been reported. (d) recombination of chemisorbed hydrogen atoms and physisorption; (e) desorption to the gas phase Among these steps, surface desorption is one of the critical processes. The presented results will advance the understanding of the hydrogen storage properties of HEAs and may promote related experimental and theoretical investigations to improve the desorption ability of HEA hydrides
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