Density Functional Theory (DFT) Computation of the Oxygen Reduction Reaction (ORR) on Titanium Nitride (TiN) Surface

Two different facets of the TiN were studied as the possible electro-catalyst for the ORR. ORR was considered to take place in three different sequential steps namely oxygen adsorption, hydroxide production and water desorption. These steps were simulated by Vienna ab initio Simulation Package (VASP) on different adsorption sites on both TiN(111) and TiN(200). Comparing the adsorption energies proved that a strong dissociative adsorption of oxygen takes place on the TiN(111) regardless of the adsorption sites. The loses of the relatively OH adsorption and desorption on TiN(111) and on TiN(200) active sites to proceed the ORR were analysed and the surface which was suitable for a easy water production and desorption was deduced. It was shown that the TiN(200) surface exhibited an active site behavior for the ORR while the TiN(111) was poisoned by strong OH adsorption. The electron density of states (DOS) was determined for these two surfaces and the d-band center and fractional filling were calculated in different situations. Considering two possible bridge and top adsorption sites on the TiN(200), the energies of the hydroxide production and water desorption were determined and it was shown that these rates are the determining steps for the ORR in bridge and top sites, respectively. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.