Water Splitting on Transition Metal Active Sites at TiO2-Based Electrodes: A Small Cluster Study

Abstract

We investigate the influence of doping TiO2 surfaces with transition metals (TMs) on the performance of TiO2-based electrodes for the water-splitting electrochemical reaction. Two cluster models of the TM-doped active sites which resemble both the TiO2 anatase (001) and rutile (110) surfaces are considered for the evaluation of the water decomposition reaction when a Ti is replaced by a TM atom. These models constitute a direct extension from our previous work in which similar representations were employed to address the water-splitting reaction on pure TiO2-based electrodes. Regarding the cluster structure as a simplified representation of an active site on the anode in the electrochemical cell, the oxygen evolution reaction (OER) is investigated using density functional theory (DFT). Simulations are carried out for a set of TMs spanning from vanadium to nickel. The proposed reaction pathways are evaluated via the variation of the free-energy profile with respect to the applied external bias. The late TM...