H ₂ In Fe ₃ O ₄ (â…¢) Adsorption And Solution From The Surface

As a renewable energy, because of its the high combustion, and the products of combustion is water, the application of hydrogen energy has aroused widespread concern, it does not cause any pollution to the environment, We can regain hydrogen through the electrolysis of water or by other methods, It is regarded as a new type of clean energy which is considered to be the most development potential energy for the human society in the coming decades. as a new type of hydrogen storage mode, Solid-state hydrogen storage materials is considered the most development potential methods for storage and transportation. Magnetite Fe3O4, a promising alternative for the hydrogen storage proposed by Otsuka et al, has attracted extensive attention. Basing on the old steam-iron process to produce hydrogen-rich fuel gas, it achieves the hydrogen storage-release processes by a simple redox reaction as following procedure:Step1:Hydrogen storage (reduction) Fe3O4+4H2â†'3Feâ†'4H2OStep2:Hydrogen recovery (oxidization)3Fe+4H2Oâ†'Fe3O4+4H2Due to the fact that the standard experimental technology, such as low-energy electron diffraction, X-ray photo-electron spectroscopy and Auger electron spectroscopy, are not sufficiently sensitive to H atom, experimental researches on hydrogen adsorption at Fe3O4surface are very limited. In this work, we report a DFT study on atomic and molecular hydrogen adsorption on Fetet1and Feoct2-terminated Fe3O4(111) surface to understand the reaction condition and hydrogen storage mechanism of Fe3O4from microscopic point of view. The Linear synchronous transit/quadratic synchronous transit (LST/QST) methods are used to search for the transition states. The activation energies and energy barriers are calculated to determine the dissociative adsorption pathway of H2. In addition, The density of the states of the two terminated Fe3O4(111) surface states including the adsorption and dissociative adsorption of H2are analyzed in detail to understand the interaction between atomic hydrogen and Fe3O4(111) surface.A detailed density functional study is performed on the adsorption and dissociative adsorption of H2on Fetet1and Feoct2-terminated Fe3O4(111) surface. Our results show clearly that S-Fetop model and E-Oc model are the most stable adsorption configuration for H2on Fetet1and Feoct2-terminated Fe3O4(111) surface with adsorption energy of-0.38eV and-0.27eV respectively. By calculated the dissociative adsorption of H2on Feoct2-terminated Fe3O4(111) surface, the dissociative adsorption pathway is from E2-Oc model to Fetop via the intermediate state of S2-Fetop model with adsorption energy of-0.48eV. By calculated the dissociative adsorption of H2on Fetet1-terminated Fe3O4(111) surface, the dissociative adsorption pathway is from S1-Fetop to Oa or Oc via a transition state with adsorption energy of-0.77eV or-0.73eV. Water molecules are generated on the Fetet1-terminated surface, remarkably in agreement with Otsuka.K’s conclusion on the reaction condition and hydrogen storage mechanism of Fe3O4from microscopic point of view. Finally, we discuss the density of states of H2adsorption and dissociative adsorption on the two terminated Fe3O4(111) surface and conclude that the models of dissociative adsorption of H2on Fe3O4(111) surface are more tempting.