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

• Published in: Journal of physical chemistry. C Vol. 120; no. 45; pp. 25851 - 25860
• Main Authors: Rodríguez-Hernández, F, Tranca, D. C, Martínez-Mesa, A, Uranga-Piña, Ll, Seifert, G
• Format: Journal Article
• Language: English
• Published: American Chemical Society 17.11.2016
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.6b08473

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 TMs explored in this workFe, Co, and Niare found to reproduce the observed experimental trends for the overpotentials in TiO2 doped electrodes. In the case of Cr and Mn, the present study predicts an enhancement of the OER activity for the anatase-like clusters while a reduction of this activity is found for the rutile-like ones. Moreover, the vanadium-doped structures do not show relevant influence in the OER activity compared to pure TiO2-based cluster models.