Cerium’s Photocatalytic Superpower: Unlocking Titanium Dioxide’s Visible Light Absorption

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A research group from the Chinese Academy of Sciences has significantly improved visible light absorption in Ce/TiO2 by doping cerium in the TiO2 lattice, resulting in a high photocurrent density and better separation efficiency of photogenerated electrons and holes. This study presents a practical strategy for developing efficient visible light-activated rare earth-doped photocatalysts.

Visible Light Absorption of Titanium Dioxide Through Cerium Synchronous Doping in Anatase

The introduction of rare earth elements into TiO2 can effectively improve the electron-hole separation of TiO2 and prolong the visible light response of TiO2.

Cerium (Ce) shows variable valence states Ce3+/Ce4+ with different electronic structures (4f15d0 and 4f05d0, respectively) among rare earth elements, which easily form oxygen vacancies. Ce element with unique electronic structure can be used to modify semiconductor photocatalysts to improve their photocatalytic performance.

In a study published in the journal Molecule, the research group led by Prof. LU Canzhong from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences, reported the visible light absorption of Ce/TiO2.

The researchers achieved simultaneous doping of Ce in the TiO2 lattice using a simple sol-gel method which achieved Ce synchronous doping in the lattice of TiO2. They observed morphology and structure of the pure TiO2, Ce-doped TiO2 (Ce/TiO2), and CeO2-mixed TiO2 (CeO2-TiO2) samples by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). They found that Ce doping in the lattice of anatase TiO2 resulted in a smaller grain size of the sample.

Besides, the researchers revealed the high photocurrent density (10.9 µA×cm-2) of Ce/TiO2 by linear sweep voltammetry (LSV) test, which is 2.5 times that of common TiO2 material (4.3 µA×cm-2). They evaluated the light absorption range of Ce/TiO2 using incident photo-to-current efficiency (IPCE) test. Ce/TiO2 shows visible light absorption up to 500 nm, while pure TiO2 shows no obvious response in the visible region.

Moreover, the researchers unveiled that the electron-trapping centers formed by Ce doping into the TiO2 lattice improved the separation efficiency of photogenerated electrons and holes. The narrow bandgap of Ce-doped TiO2 showed excellent visible light absorption and photocurrent response. Due to the Ce doping, the Ce/TiO2 samples achieved high photocurrent density and incident photon current efficiency (IPCE).

This study provides a practical strategy and an important reference for the preparation and understanding of highly efficient visible light-activated rare earth-doped photocatalysts.

Reference: “Cerium Synchronous Doping in Anatase for Enhanced Photocatalytic Hydrogen Production from Ethanol-Water Mixtures” by Mei-Hong Tong, Yan-Xin Chen, Tian-Ming Wang, Shi-Wei Lin, Gen Li, Qian-Qian Zhou, Rui Chen, Xia Jiang, Hong-Gang Liao and Can-Zhong Lu, 7 March 2023, Molecule.
DOI: 10.3390/molecules28062433

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