Abstract
To investigate Mo doping effects on the hydrogen permeation performance of Nb membranes, we study the most likely process of atomic hydrogen adsorption and diffusion on/into Mo-doped Nb (100) surface/subsurface (in the Nb12Mo4 case) via first-principles calculations. Our results reveal that the (100) surface is the most stable Mo-doped Nb surface with the smallest surface energy (2.75 J/m2). Hollow sites (HSs) in the Mo-doped Nb (100) surface are H-adsorption-favorable mainly due to their large adsorption energy (−4.27 eV), and the H-diffusion path should preferentially be HS→TIS (tetrahedral interstitial site) over HS→OIS (octahedral interstitial site) because of the correspondingly lower H-diffusion energy barrier. With respect to a pure Nb (100) surface, the Mo-doped Nb (100) surface has a smaller energy barrier along the HS→TIS pathway (0.31 eV).
Highlights
Over 80 percent of synthetic chemicals are produced with the application of catalysts, meaning that the interactions of hydrogen with catalytic metal surfaces during heterogeneous catalysis are of great interest for several important processes [6,7,8] including petrochemical processing, pharmaceutical production [9], highly efficient electrocatalysis [10], fine chemical production [11], and conversion of biomass to fuels and chemicals [12]
To gain a detailed understanding of the hydrogen-permeation behavior of Mo-doped Nb membranes, adsorption and diffusion of hydrogen atoms on a Mo-doped Nb (Nb12 Mo4 ) surface have been investigated by first-principles calculations in this work
An energy cutoff of 360 eV was used for the plane-wave basis sets, and a grid with 2π × 0.03 Å−1 resolution in the Brillouin zone was used for all calculations to minimize the error from the k-point meshes
Summary
The interaction between hydrogen and metal surfaces is an interesting topic in science and engineering, and has been investigated by both experimental [1,2,3] and theoretical [4,5] approaches. H has higher diffusivity and lower solubility in Mo, leading to lower H retention [33,34,35] These characteristics make Mo an important alloying candidate of Nb-based membranes for hydrogen permeation. To gain a detailed understanding of the hydrogen-permeation behavior of Mo-doped Nb membranes, adsorption and diffusion of hydrogen atoms on a Mo-doped Nb (Nb12 Mo4 ) surface have been investigated by first-principles calculations in this work. We believe this work is important to comprehensively understand the basic mechanism of atomic hydrogen sorption on TM surfaces and the influence of element doping, and contribute to the design of Nb-based alloys for H-storage and H-separation applications
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