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.