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 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.

Insights into the carbonate effect on water oxidation over metal oxide photocatalysts/photoanodes

“…S2 in the ESI†). 18 In B02 , the molecular adsorption of H 2 O due to the Bi⋯O interaction with a distance of 2.688 Å occurred, and this was analogous to the DFT results obtained by Li and coworkers. 15 The first deprotonation from the adsorbed H 2 O was largely endergonic ( B03 ), as in the corresponding step on TiO 2 ( T02 → T03 , Fig.…”

“…In this study, we focus on the photoinduced oxidation of H 2 O and carbonic acid (H 2 CO 3 ) on TiO 2 and BiVO 4 using quantum chemical calculations at the DFT level. According to a commonly accepted theoretical description that consists of four proton-coupled electron-transfer (PCET) steps with two H 2 O molecules, 14–19 the intermediate and oxidation mechanisms of H 2 CO 3 , as well as H 2 O, are investigated using molecular cluster models. By identifying the cause of the effect of carbonate, the variety of available photocatalysts/photoelectrodes and that of the products from H 2 O and solar energy for sustainable development should be extended.…”

Photooxidation of Water on Pristine, S- and N-Doped TiO2(001) Nanotube Surfaces: A DFT + U Study

“…The large overpotential required for the OER is known to be a serious restraint to PEC water splitting and has motivated many investigations for finding efficient ways to lower it (see, e.g., ref for a review). Because of its many beneficial properties, such as chemical and optical stability, nontoxicity, low cost, as well as abundance, TiO 2 has been one of the most studied photoanode materials. − A few studies have shown that water splitting on TiO 2 also suffers from such large overpotentials, especially on the anatase surface, where overpotentials larger than 1 eV have been recorded for the OER. , …”

“…5−7 A few studies have shown that water splitting on TiO 2 also suffers from such large overpotentials, especially on the anatase surface, where overpotentials larger than 1 eV have been recorded for the OER. 8,9 Several recipes have been proposed to reduce the OER overpotential on TiO 2 and to broaden the light absorption spectra so as to cover the visible region. One such recipe is to couple TiO 2 with Cu 2 O and CuO nanoparticles or clusters.…”

Tandem Cu2O-covered silicon micropillar photocathodes for solar-to-fuel devices

“…Unstable semiconductors are being coated with nanometer scale thin films of materials including metals or metal silicides, [106][107][108][109] wide band gap semiconductors, 110 transparent conducting oxides, 111,112 transition metals and their oxides, 113,114 and organic polymers. 115 Most recent studies deal with the fabrication of these using ALD, 116 which allows for ultra-thin films with limited charge transfer resistance.…”