The electric double layer at a rutile TiO₂ water interface modelled using density functional theory based molecular...

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Understanding the electric double layer (EDL) at the rutile titanium dioxide (TiO2) (110) water interface is crucial for various electrochemical applications.
• Protonation states and counter-ion coordination significantly influence surface properties and interfacial behavior.

Purpose of the Study:

• To construct a fully atomistic model of the EDL at the rutile TiO2(110)-water interface.
• To determine the capacitance of the interface for different protonation states and counter-ion coordination (inner vs. outer sphere).

Main Methods:

• Utilized density functional theory (DFT) based molecular dynamics simulations.
• Calculated the free energy for electron and proton insertion to determine the TiO2 conduction band minimum relative to the standard hydrogen electrode.
• Computed capacitance from electrode potentials and electrostatic potential differences.

Main Results:

• Developed an atomistic model for the EDL at the rutile TiO2(110)-water interface.
• Inner sphere complexes exhibited a slightly higher capacitance (0.4 F m(-2)) compared to outer sphere complexes (0.3 F m(-2)).
• Two distinct methods for capacitance calculation yielded nearly identical potential-charge profiles when aligned at the point of zero charge.

Conclusions:

• The study provides atomistic insights into the capacitance of the rutile TiO2-water interface.
• Inner sphere complexation enhances interfacial capacitance, relevant for designing TiO2-based electrochemical devices.
• The findings validate computational approaches for predicting interfacial properties in semiconductor-water systems.