基于插层化学的单晶氧化钨纳米片的制备、表征与形成机制

结合插层化学与湿化学方法的优点, 建立了一种高比表面积、大径厚比、易分散的二维氧化钨(WO3)纳米片单晶的制备新方法. 微米级WO3与Bi2O3在800 ℃通过固相反应生成层状化合物Bi2W2O9; 所得到的Bi2W2O9经盐酸选择性溶出[Bi2O2]层后得到质子化形式的H2W2O7·xH2O相. 以H2W2O7·xH2O为钨源, 以辛胺插层所得无机-有机混杂纳米带为前驱物, 经硝酸氧化除去前驱物中的有机组分后得到正交相WO3·H2O纳米片; 将所得到的WO3·H2O纳米片在250~ 450 ℃和空气气氛中热处理2~5 h(升温速率为2 ℃/min), 得到单斜相WO3单晶纳米片. TEM与SEM分析结果表明, 单晶WO3·H2O与WO3纳米片的形貌相似, 其大小为(200~500) nm×(200~500) nm, 厚度为10~30 nm; 所得WO3·H2O与WO3纳米片单晶的厚度方向分别为[010]和[001]. N2吸附结果表明, WO3·H2O与WO3纳米片的比表面积分别可达到250与180 m2/g.

Synthesis, Characterization and Formation Mechanism of Single-Crystal WO3 Nanosheets via an Intercalation-chemistry-based Route

In this work an intercalation-chemistry-based method to synthesize tungstate and tungsten oxide nanosheets was described. A layered bismuth tungstate(Bi2W2O9) was used as the W-containing starting material. After the bismuth oxide layers were leached by a chloride acid, a protonated form, H2W2O7·xH2O with sizes of 5—15 μm, was achieved. The intercalation reaction of n-octylamine with H2W2O7·xH2O in heptane and the subsequent dissolution-recrystallization process led to the formation of tungstate-based inorganic organic hybrid nanobelts. Orthorhombic WO3·H2O nanosheets were obtained by removing the organic species of the as-obtained hybrid nanobelts. After the dehydration of the as-obtained WO3·H2O nanosheets at 250—450 ℃, monoclinic WO3 nanosheets were achieved. The results of XRD, TEM and SEM indicate that the obtained WO3·H2O and WO3 were single-crystalline nanosheets with areas of (200—500) nm×(200—500) nm and thicknesses of 10—30 nm. The SAED patterns suggest that the WO3·H2O and WO3 nanosheets possessed a reduced directions of [010] and [001], respectively. N2 adsorption measurement results indicate that the specific surface areas of the as-obtained WO3·H2O and WO3 nanosheets were up to 250 and 180 m2/g, respectively. The formation mechanisms for hybrid nanobelts, WO3·H2O and WO3 nanosheets were discussed. The proposed novel route was efficient in producing two-dimensional WO3 nanosheets on a large scale.