Cu_3B_2O_6/CuB_2O_4单晶的制备及其可见光催化降解亚甲基蓝

以醋酸铜/硝酸铜和硼酸为原料,柠檬酸作发泡剂,采用溶胶-凝胶法制得了高纯度的单晶结构硼酸铜(Cu3B2O6/CuB2O4).利用X射线衍射(XRD)、扫描电镜(SEM)、高分辨率透射电镜(HRTEM)、热重-差热分析(TGDTA)等对样品进行了表征,并考察了Cu3B2O6/CuB2O4在可见光(400 nmλ1100 nm)下对亚甲基蓝(MB)溶液的催化降解性能.结果表明,两种结构的硼酸铜都具有良好的光催化性能.当亚甲基蓝的初始浓度为50 mg·L-1,催化剂用量为1 g·L-1,光照6 h后,CuB2O4对亚甲基蓝的光催化降解率为63.36%,Cu3B2O6对亚甲基蓝的光催化降解率为99.52%.紫外-可见漫反射光谱(UV-Vis DRS)结果表明,Cu3B2O6的中间能态宽度为1.78 eV,小于CuB2O4的中间能态宽度(1.95 eV),且Cu3B2O6的禁带宽度较窄(Eg=2.34 eV),不仅可以发生价带顶与中间能态的电子跃迁,同时可以发生禁带间的电子跃迁,所以Cu3B2O6比CuB2O4具有更高的可见光催化性能.

Synthesis of Single-Crystalline Cu3B2O6/CuB2O4 and Their Photocatalytic Degradation of Methylene Blue under Visible-Light Irradiation

Single-crystalline Cu₃B₂O₆/CuB₂O₄ was successfully prepared by a sol-gel method fromcupric nitrate/ cupric acetate and boric acid, using citric acid as a foaming agent. The obtained materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and thermogravimetry-differential thermal analysis (TG-DTA). The photodegradation of methylene blue (MB) solution was used to evaluate the photocatalytic activity of Cu₃B₂O₆/CuB₂O₄ under visiblelight irradiation (400 nm<λ<1100 nm). The results indicated that both Cu₃B₂O₆ and CuB₂O₄ displayed good photocatalytic activity. Under visible-light irradiation for 6 h, the photocatalytic activities of CuB₂O₄ and Cu₃B₂O₆ reached 63.36% and 99.52%, respectively, in MB aqueous solution (50 mg·L^-1) containing 1 g·L^-1 catalyst. Ultraviolet-visible analysis showed that the width of the midgap state for Cu₃B₂O₆ is 1.78 eV, which is much narrower than that of CuB₂O₄ (1.95 eV), and the band gap of Cu₃B₂O₆ is narrow (E_g=2.34 eV). These results indicated that electron transitions can occur in both the midgap state and forbidden band for Cu₃B₂O₆; this is why Cu₃B₂O₆ has higher visible-light photocatalytic activity than CuB₂O₄.