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Tuning the water-splitting mechanism on titanium dioxide surfaces through hydroxylation
Lu Wu1,2, Meijing Liao2, Bing Zhao2
1Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, Shandong Universities Engineering Research Center of Integrated Circuits Functional Materials and Expanded Applications, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, P. R. China. zhangyuexing@sdu.edu.cn.
Surface hydroxyl groups significantly enhance titanium dioxide (TiO2) for water splitting. This study clarifies the mechanism and roles of these hydroxyl groups in the oxygen evolution reaction (OER), guiding future catalyst development.
Area of Science:
- Materials Science
- Physical Chemistry
- Catalysis
Background:
- Surface hydroxyl groups are known to enhance TiO2's water-splitting capabilities.
- The precise mechanism and role of these hydroxyl groups in water splitting remain unclear.
- Hydroxyl groups on TiO2 surfaces can form via H2O or H2 cracking, categorized as type I (OH1) and type II (OH2).
Purpose of the Study:
- To systematically investigate the water oxidation mechanism on hydroxylated TiO2 surfaces.
- To elucidate the varying roles of hydroxyl groups in the oxygen evolution reaction (OER) and product selectivity.
- To provide insights for developing efficient water-splitting catalysts based on hydroxylated TiO2.
Main Methods:
- Construction of six hydroxylated TiO2 surfaces: anatase (101), rutile (110), and brookite (210) with OH1 and OH2 groups.
- Density functional theory (DFT) calculations to study the water oxidation process.
- Thermodynamic analysis of the OER pathway and surface overpotentials.
Main Results:
- All studied hydroxylated TiO2 surfaces produce oxygen via a four-electron/proton process, distinct from pure TiO2.
- Surface overpotentials range from 0.53 V (R-110-OH1) to 1.49 V (B-210-OH2).
- Rutile (110) and brookite (210) surfaces with OH1-type hydroxyl groups are more favorable for the OER process.
Conclusions:
- Hydroxylated TiO2 surfaces exhibit a unique OER mechanism compared to pure TiO2.
- The type and configuration of hydroxyl groups significantly influence OER efficiency and thermodynamics.
- Specific hydroxylated TiO2 facets, particularly rutile (110) and brookite (210) with OH1, show promise for catalytic water splitting.
