Mechanism of Electrochemical Hydrogen Storage for α-Fe2O3 Particles as Anode Material for Aqueous Rechargeable Batteries

In this work, a new mechanism is proposed to describe hydrogen storage using alpha-Fe2O3 particles as an anode material in an aqueous solution. According to this mechanism, the transfer of H+ in the Fe2O3 lattice plays an important role in the hydrogen storage process. This mechanism, which was based on a conventional theoretical description of the electrochemical reaction of Fe2O3 in an aqueous solution, also included the reaction of H+ in the interior of the Fe2O3 particles. The entrance and separation of H+ in the interior of the Fe2O3 particles were instrumental to the charge/discharge processes at the anode. The tetrahedral oxygen interspace in the Fe2O3 lattice was an optimum size for H+ transport. Charge/discharge cycling and X-ray diffraction experiments were also performed. Using a first-principle simulation, covalent bonding was found to be possible between H+ and O in the interior of a Fe2O3 particle, and the lowest energy location for this bonding was in the tetrahedral oxygen interspace. These findings provide a more comprehensive understanding of the electrochemical reactions between Fe2O3 and water. (C) 2016 The Electrochemical Society. All rights reserved.