Degradation in photocatalytic activity induced by hydrogen-related defects in nano-LiNbO3 material

Abstract

As a representative example, nano-$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ is prepared by a wet-chemical method in order to enhance its photocatalytic activity through improving the surface area. The samples perform good crystallinity from powder x-ray diffraction and transmission-electron-microscope observations. It is surprising that photocatalytic activity of nano-$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ decreases with an increase of its surface area. The presence of hydrogen in the as-prepared $\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ samples is detected by measuring the $\mathrm{O}{\mathrm{H}}^{-}$ absorption that occurred near $3500{\mathrm{cm}}^{-1}$ in infrared spectra. Though the surface area of the nano-$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ samples with good crystallinity increases with a decrease of the sintered temperature, the number of hydrogen-related defects in the samples increases noticeably, thus reducing the photocatalytic activities of the nano-$\mathrm{Li}\mathrm{Nb}{\mathrm{O}}_3$ samples.