Electrochemical and photoelectrochemical characteristics of TiNbO5 nanosheet electrode

Exfoliated TiNbO5 nanosheets were obtained by delaminating a layered compound KTiNbO5. Employing a layer-by-layer electrostatic deposition technology, the exfoliated nanosheets were deposited into a multilayer composite film with polyethylenimine as the linker, confirmed by UV–vis absorption spectra and X-ray diffraction. The polymer-free TiNbO5 nanosheet multilayer film was achieved through the subsequent ultraviolet light exposure. The cyclic voltammogram of the resulting TiNbO5 nanosheet multilayer film electrode exhibited a reversible reduction–oxidation process of Ti3+/Ti4+, accompanying with the insertion/deinsertion of Li+ ions into/from the nanosheet galleries. The bandgap energy and flatband potential of TiNbO5 nanosheet were observed to be 3.47 eV and −1.01 V vs. Ag/AgCl, respectively. The investigation on the photoelectrocatalytic degradation of Rhodamine B with the TiNbO5 nanosheet electrodes revealed that both the oxygen anionic radicals and the dye cationic radical are essential for the mineralization of the dye under visible light-driven photocatalytic conditions, and that the electron separation under an anode bias can suppress the rapid recombination of the photogenerated charge carriers under ultraviolet light irradiation. It is the first time to investigate the mechanism of photoelectrocatalysis for TiNbO5 nanosheet electrode.

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► TiNbO5 nanosheet-film electrode exhibited a reversible reduction–oxidation process.
► The flatband potential was determined as −1.01 V vs. Ag/AgCl.
► The oxygen anionic radicals are essential to mineralize the dye under visible light irradiation.
► An anode bias can suppress the rapid recombination of the photogenerated charge carriers.