Water oxidation by P25 TiO₂ photoanodes in acidic solution

Area of Science:

• Materials Science
• Electrochemistry
• Photochemistry

Background:

• Titanium dioxide (TiO2) is a key material for photoelectrochemical water splitting.
• Understanding the kinetics of water oxidation on TiO2 photoanodes is crucial for improving solar fuel production.

Purpose of the Study:

• To investigate the photoelectrochemical behavior of P25 TiO2 photoanodes in different acidic electrolytes.
• To elucidate the kinetics of water photo-oxidation on P25 TiO2 using advanced spectroscopic and transient photocurrent techniques.

Main Methods:

• Linear sweep voltammetry (LSV) to analyze photocurrent responses.
• Photo-induced absorption spectroscopy (PIAS) to monitor surface-accumulated holes.
• Transient photocurrent (TC) measurements to determine reaction kinetics.

Main Results:

• P25 TiO2 exhibited distinct photocurrent behaviors in 0.5 M H2SO4 and 1 M HClO4.
• In 1 M HClO4, high faradaic efficiency for O2 evolution (0.91) indicated efficient water oxidation.
• PIAS and TC measurements revealed a second-order dependence of water oxidation on surface-accumulated holes, with a turnover frequency of 19 s-1 under 1 sun irradiation.

Conclusions:

• The study successfully employed PIAS/TC to probe photoelectrochemical kinetics of mesoporous TiO2 for water oxidation.
• Water oxidation kinetics on P25 TiO2 in 1 M HClO4 are governed by surface-accumulated holes.
• This work provides insights into optimizing TiO2-based photoanodes for efficient water splitting.