金属有机骨架和g-C_(3)N_(4)共掺杂改性TiO_(2)光催化性能

Photocatalytic performance of TiO_(2) co-doped with metal organic framework and g-C_(3)N_(4)

以钛酸四丁酯、三聚氰胺、二甲基咪唑和Co(NO_(3))_(2)•6H_(2)O为原料,采用溶胶-凝胶法、高温煅烧法,将类石墨相氮化碳(g-C_(3)N_(4))和二甲基咪唑钴(ZIF-67)与TiO_(2)共掺杂,制备了TiO_(2)-g-C_(3)N_(4)-ZIF-67光催化剂。采用XRD、XPS、SEM和紫外-可见漫反射光谱(UV-Vis DRS)对TiO_(2)-g-C_(3)N_(4)-ZIF-67进行了表征,对TiO_(2)-g-C_(3)N_(4)-ZIF-67光催化降解甲基橙的催化活性进行了评价,并对其催化机理进行了推测。结果表明,TiO_(2)-g-C_(3)N_(4)-ZIF-67同时包含锐钛矿及少量金红石相TiO_(2)、g-C_(3)N_(4)及ZIF-67;g-C_(3)N_(4)的加入使TiO_(2)的带隙降至2.45 eV,ZIF-67将带隙进一步降至1.91 eV;g-C_(3)N_(4)和ZIF-67的共掺杂降低了带隙,显著提高了TiO_(2)可见光吸收范围(492~649 nm);TiO_(2)-g-C_(3)N_(4)-ZIF-67形成了Ⅱ型异质结,TiO_(2)-g-C_(3)N_(4)与金属有机骨架的结合增强了TiO_(2)光催化降解甲基橙的能力。Co质量分数21.5%的TiO_(2)-g-C_(3)N_(4)-ZIF-67-2具有最佳的光催化降解甲基橙活性,在可见光照射40 min时,甲基橙降解率可达79.92%,3次循环后甲基橙降解率为58.86%(90 min),光催化反应对ZIF-67的结晶度有所影响,进而影响了循环时的光催化活性。

TiO_(2)-g-C_(3)N_(4)-ZIF-67 photocatalysts were prepared by co-doping graphite-like phase carbon nitride(g-C_(3)N_(4))and dimethylimidazole cobalt(ZIF-67)with TiO_(2)using sol-gel and high temperature calcination method using tetrabutyl titanate,melamine,dimethylimidazole and Co(NO_(3))_(2)•6H_(2)O as raw materials,and then characterized by XRD,XPS,SEM,and ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS).The photocatalytic activity of TiO_(2)-g-C_(3)N_(4)-ZIF-67 on Methyl Orange degradation was evaluated,with the catalytic mechanism speculated.The results showed that TiO_(2)-g-C_(3)N_(4)-ZIF-67 contained both anatase and a small amount of rutile-phase TiO_(2),g-C_(3)N_(4)and ZIF-67.The addition of g-C_(3)N_(4)decreased the bandgap of TiO_(2)to 2.45 eV,while the addition of ZIF-67 further reduced it to 1.91 eV,which significantly increased the visible light absorption range of TiO_(2)(492~649 nm).Meanwhile,TiO_(2)-g-C_(3)N_(4)-ZIF-67 formed a typeⅡheterojunction,and the combination of TiO_(2)-g-C_(3)N_(4)with metal-organic framework enhanced the photocatalytic degradation of Methyl Orange,with TiO_(2)-g-C_(3)N_(4)-ZIF-67-2 with Co mass fraction of 21.5%exhibiting the best photocatalytic performance of degradation rate reaching 79.92%at 40 min of visible light illumination and 58.86%(90 min)after three cycles,showing good stability of catalyst.The photocatalytic reaction had an effect on the crystallinity of the ZIF-67,thus affecting the photocatalytic activity during the cycles.