A first-principles study on the effect of Hf on the hydrogen evolution of ZrCoH3
The transition metal element Hf is designed to be added to ZrCoH3 by occupying Co atoms,Zr atoms and interstitial sites.The effect of Hf on the hydrogen evolution of ZrCoH3 are investigated by first-principles calculations.It is found that substitution with Hf destabilizes ZrCoH3,leading to a reductions in the dehydrogen-ation energy(Ed)and the Co-H average bond length with the order of Zr16Co16H48>Zr16Co16HfH48>Zr16Co15HfH48>Zr15Co16HfH48.Theoretical studies show that in the ZrCoH3-Hf system,the weaker Co-H covalent bond interaction,metallic properties and the formation of Hf-H bonds are all beneficial to improve the hydrogen release capacity of ZrCoH3.Hf atoms preferentially occupy interstitial sites,but this has little effect on the hydro-gen dissociation energy.Although the Zr15Co16HfH48 compound has low hydrogen dissociation energy and exhibits good hydrogen desorption performance,it needs to consume too high energy cost when Hf occupies Zr site in practical application.
Hydrogen storageZrCoH3First-principles calculationsDehydrogenation performanceTransition metal element doping
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