Molten Salt Synthesis of Bi2WO6 Powders and its Visible-Light Photocatalytic Activity

Bi2WO6 powders were synthesized by the molten salt method at 250-350 ºC using the mixture of Bi(NO3)3·5H2O and Na2WO4·2H2O as a precursor, and the mixture of LiNO3 and NaNO3 with a molar ratio of 27:33 as a molten salt, respectively. The effects of temperature and salt amount on the phase composition, morphology and photocatalytic activity under the visible light irradiation were investigated. The results revealed that pure phase Bi2WO6 powders could be synthesized at 350 ºC as the weight of molten salts were 2‒5 times as many as the precursor. Bi2WO6 powder synthesized with lower salt amount exhibited larger surface area, more abundant pores, narrower bandgap and lower PL intensity, all of which contributed a higher photocatalytic activity. The synthesized Bi2WO6 powder could degrade 0.01 mol/L Rhodamine-B solution by 97% after irradiation under visible light for 60 min. The obtained Bi2WO6 powder had a good photochemical stability and reusability, revealing potential application in environmental treatment.

本研究以五水合硝酸铋（Bi(NO3)3·5H2O）与二水合钨酸钠（Na2WO4·2H2O）的混合物作为前驱体，以摩尔比为27:33的硝酸锂（LiNO3）与硝酸钠（NaNO3）混合物作为熔盐介质，通过熔盐法在250~350 ℃的条件下合成了钨酸铋（Bi2WO6）粉体。考察了合成温度与熔盐用量对产物相组成、形貌以及可见光照射下光催化活性的影响。结果显示，当熔盐用量为前驱体质量的2~5倍时，可在350 ℃下合成纯相钨酸铋粉体。低熔盐用量条件下合成的钨酸铋粉体具有更大的比表面积、更丰富的孔结构、更窄的禁带宽度以及更低的光致发光（PL）强度，上述特性共同赋予其更优异的光催化性能。所合成的钨酸铋粉体在可见光照射60 min后，可将0.01 mol/L的罗丹明B（Rhodamine B）溶液降解97%。所得钨酸铋粉体具备良好的光化学稳定性与重复使用性能，在环境污染治理领域展现出潜在应用价值。