稀土Ce掺杂对ZnO结构和光催化性能的影响

采用共沉淀-焙烧法合成了一系列不同含量的稀土Ce掺杂的ZnO光催化剂. 利用傅里叶变换红外(FT-IR)光谱、粉末X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)光谱、光致发光(PL)谱等技术对所制备的光催化剂进行了系列表征. 以酸性橙II脱色降解为模型反应, 考察了掺杂不同含量的铈及不同焙烧温度对ZnO的物理结构和光催化脱色性能的影响. 结果表明: 掺入质量分数(w)为2%的铈可以明显改善氧化锌表面状态, 有利于产生更多的表面羟基; 同时可以抑制光生电子与光生空穴(e^-/h⁺)的复合, 显著提高光催化脱色活性和光催化稳定性; 焙烧温度对光催化剂的晶体结构、表面性能和光催化活性产生较大影响, 500 °C的焙烧处理使样品的结晶度较高, 同时催化剂颗粒粒径较细, 表面具有丰富的羟基. 但过高的焙烧温度(600-800 °C)将导致催化剂的物理结构发生恶化, 降低光催化性能.

Effects of Rare Earth Ce Doping on the Structure and Photocatalytic Performance of ZnO

A series of ZnO photocatalysts doped with different amounts of cerium were prepared by co-precipitation and then calcined at different temperatures. The prepared pure ZnO and Ce-doped ZnO samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), UV-visible (UV-Vis) spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic activity of the samples was evaluated by the photodegradation of acid orange II under UV light (λ=365 nm) irradiation. FT-IR results showed that ZnO doped with 2% (w, mass fraction) cerium had far more OH groups over the surface of the doped sample than the pure ZnO. At the same time, PL tests indicated that the presence of 2% (w) cerium effectively suppressed the recombination of the photogenerated hole-electron pairs. On the other hand, the calcination temperatures influenced the crystallinity and crystal size of the catalysts. XRD tests indicated that the sample calcined at 500 °C had good crystallinity and a small crystal size while elevated temperature treatment (600-800 °C) would result in sintering and increase the crystal size. At the optimal calcination temperature of 500 °C and at 2% (w) cerium doping the composite photocatalyst had much higher photocatalytic activity and stability compared with pure ZnO. The high photocatalytic performance of the Ce doped ZnO could be attributed to an increase in surface OH groups, high crystallinity and a low recombination rate of electron/hole (e^-/h⁺) pairs.