The Effects of Li/Nb Ratio on the Preparation and Photocatalytic Performance of Li-Nb-O Compounds

The effects of Li/Nb ratio on the preparation of Li-Nb-O compounds by a hydrothermal method were studied deeply. Li/Nb ratio has a great impact on the formation of LiNbO(3); the ratio smaller than 3:1 is beneficial to the formation of LiNbO(3), while larger than 3:1, forms no LiNbO(3) at all and the morphology and chemical bond of Nb(2)O(5) raw material are totally modified by Li ions. The reason can be attributed to the large content of LiOH, which is beneficial to form Li(3)NbO(4) not LiNbO(3), and also, even if LiNbO(3) particle locally forms, it is easily dissolved in LiOH solution with strong alkalinity. Pure LiNb(3)O(8) powders are obtained with two absolutely opposite Li/Nb ratios: 8:1 and 1:3; the former shows a unique porous and hollow structure, quite different from the particle aggregation (the latter shows). Compared with Li/Nb = 1:3, the 4.2 times higher photocatalytic performance of LiNb(3)O(8) (Li/Nb = 8:1) are observed and it can be attributed to the unique porous and hollow structure, which provides a high density of active sites for the degradation of MB. Compared to LiNbO(3), the improved photocatalytic performance of LiNb(3)O(8) can be attributed to its layered structure type with the reduced symmetry enhancing the separation of electrons and holes.