OER trends on TiO₂ anatase hydroxylated surfaces: a DFT study.

Area of Science:

• Surface Science
• Computational Chemistry
• Electrochemistry

Background:

• Limited research exists on the influence of hydroxylated titanium dioxide (TiO2) surfaces on the oxygen evolution reaction (OER).
• Understanding these effects is crucial for developing efficient electrocatalysts.

Purpose of the Study:

• To systematically investigate the impact of varying degrees of hydroxylation and oxygen coverage on anatase TiO2 (100) and (101) surfaces during OER.
• To explore the changes in OER mechanisms and active sites under different surface conditions.

Main Methods:

• Density functional theory (DFT) calculations were employed to model TiO2 surfaces with six degrees of hydroxylation and varying oxygen coverage.
• A thermodynamic model was used to analyze reaction mechanisms and active sites.
• Analysis focused on the balance of electrons between donor and acceptor groups and its effect on adsorption energies and Fermi level.

Main Results:

• Different OER mechanisms (associative, binuclear) were predicted based on hydroxylation levels and oxygen coverage.
• Highly hydroxylated surfaces favored associative mechanisms, while moderate hydroxylation showed competition between associative and binuclear mechanisms.
• Electron donor-acceptor balance strongly influenced adsorption energies of OER intermediates and theoretical overpotentials, more so than surface coverage.

Conclusions:

• Surface hydroxylation and oxygen coverage on TiO2 significantly alter OER mechanisms and energetics.
• The electronic interplay between surface groups is a key factor in determining OER performance.
• Optimizing TiO2 surface properties through controlled hydroxylation and electron balance can lead to lower theoretical overpotentials for OER.