An ab-initio study of hydrogen atom diffusion in metal-oxides for energy conversion

As an outcome of the reduction of reliance on fossil fuels as the main energy source, different solutions had been developed as an alternative energy sources. One of the main techniques is water splitting using photocatalytic process in order to gather H₂. The hydrogen molecules are then used to produce electricity via electrochemical reaction in a fuel cell.

Both splitting water and the reverse process in the fuel cell involve proton transport. In This study, DFT calculations have been done for migration of H atom inside a metal-oxide anode during the oxygen evolution reaction (OER). Additionally, hydrogen diffusion through vacancies in the metal-oxide has been investigated. The results shows low energy barriers for hydrogen transport, suggesting that hydrogen migration inside the anode is plausible and might affect the efficiency. Furthermore, calculations shows low energy barrier and possible pathway for hydrogen hopping between vacancies in the bulk material.

The main method that was used in purpose to find energy barrier and minimum energy path (MEP) for hydrogen atom transport was `Nudged Elastic Band` (NEB). The NEB is a chain-of-states method for discovering MEP between known initial and final states. The method optimizes guessed states between the initial and final ones while maintaining equal spacing between adjacent states and minimizing the energy for each state.