First-Principles Studies on Deoxidizing Mechanism of V$_{\mathrm{2}}$O$_{\mathrm{5}}$ via Hydrogen

With its high melting point, good plasticity and good corrosion resistance at low temperatures, vanadium has been widely used in the industries of iron and steel, aviation, energy storage, etc. However, the traditional manufacturing technologies of pure vanadium are usually connected with complex manufacturing processes, high costs and serious environment pollution, which more or less hindered its further applications. Recently, hydrogen gas has been considered as a promising reducing agent of V$_{\mathrm{2}}$O$_{\mathrm{5}}$, but experimental studies of deoxidization process of V$_{\mathrm{2}}$O$_{\mathrm{5}}$ single crystal surfaces were found to be extremely difficult. In this work, we perform extensive \textit{ab initio} studies on~the structural and electronic properties of different V$_{\mathrm{2}}$O$_{\mathrm{5}}$ surfaces, as well as the adsorption sites, diffusion and desorption processes of H on these surfaces as a dependence of depth. We found that H atoms adsorb at oxygen site to form surface hydroxyl (OH$^{\mathrm{-}})$ and further to form H$_{\mathrm{2}}$O on V$_{\mathrm{2}}$O$_{\mathrm{5}}$(010) surfaces, and the latter is easier to be desorbed compared with the former. But the desorption of H$_{\mathrm{2}}$O causes significant surface reconstructions, which makes the further deoxidization of V$_{\mathrm{2}}$O$_{\mathrm{5}}$ difficult, particularly on the V$_{\mathrm{2}}$O$_{\mathrm{5}}$ single-layer. Our theoretical results are instructive for understandings of the reduction mechanism of V$_{\mathrm{2}}$O$_{\mathrm{5}}$ by using a green agent of H$_{\mathrm{2}}$, and furthermore for the design of new experiments$_{\mathrm{.}}$