锌尖晶石ZnM_2O_4(M=Cr，Mn，Fe)纳米晶的制备及其在可见光下对染料的光催化降解(英文)

PREPARATION AND PHOTOCATALYTIC DEGRADATION BEHAVIORS TO DYES OF ZINC SPINEL ZnM_2O_4(M=Cr,Mn,Fe) NANOCRYSTALS UNDER VISIBLE LIGHT IRRADIATION

采用无机盐溶胶-凝胶法,以硝酸锌、硝酸铁、硝酸铬、硝酸锰为原料,柠檬酸为络合剂.在空气气氛中,制得干凝胶经600℃热处理制备了系列锌尖晶石ZnM_2O_4(M=Cr,Mn,Fe)纳米粉体。用X射线衍射仪和透射电子显微镜分别对粉体的结构、形貌进行了分析和表征。结果表明:制备的ZnCr_2O_4,ZnMn_2O_4和ZnFe_2O_4粉体均为单一尖晶石晶体结构,呈不规则颗粒状,粒径为10～35nm。通过紫外-可见漫反射吸收光谱,得到吸收极限波长分别红移至400,600,680 nm,具有较好的可见光响应。在高压汞灯(λ>400 nm)和太阳光照射下,纳米ZnM_2O_4(M=Cr,Mn,Fe)粉体对甲基橙、酸性红B、活性艳红K-2G等有机模拟降解液的2h脱色降解率分别达到80%,57%和39%以上,表明锌尖晶石ZnM_2O_4(M=Cr,Mn,Fe)光催化剂具有良好的可见光催化活性,并随禁带宽度E_g的减小,催化活性增加。根据无机固体化学能带理论和晶体场理论,依据M—O电负性和d电子数量讨论了它们光催化活性的差别。

Zinc spinel ZnM2O4 （M=Cr, Mn, Fe） nanoparticles were prepared from dry gel using an inorganic salt sol-gel method and calcination in air at 600 ℃. The crystalline structure and morphology were characterized by powder X-ray diffraction and transmission electron microscopy. The results indicate that ZnCr2O4, ZnMn2O4 and ZnFe2O4 powders possess a single spinel-type structure. The particles have an irregular shape with the sizes of 10-35 nm. The absorption edge wavelengths of ZnCr2O4, ZnMn2O4 and ZnFe2O4 crystals are 400, 600 nm and 680 nm, respectively, in ultraviolet-visible diffuse reflectance spectra. The photocatalytic degradation property of ZnM2O4 （M=Cr, Mn, Fe） nanoparticles was investigated by using methyl orange, acid red B and reactive red K-2G as model pollutants under the irradiation of a mercury-vapor lamp （2〉400 nm） or sunlight. The degradation rates of the above three dyes by ZnM2O4（M=Cr, Mn, Fe） are over 80%, 57% and 39%, respectively within 2 h. It is found that ZnM204 （M=Cr, Mn, Fe） has a novel photocatalytic behavior for dyes under visible light irradiation. And with the decrease of band gap energy （Eg） of ZnM204 （M=Cr, Mn, Fe）, the catalytic activity increases steadily. The possible reason for this activity change is discussed from the crystal field theory and energy band theory.