掺杂ZnO光催化剂研究进展

ZnO作为半导体光催化剂，具有无毒性、高效性和低成本等优点得到广泛研究。但是ZnO禁带宽度较宽，为3.37 eV，仅能吸收紫外光，而且光生电子和空穴较容易复合，在太阳光照射下，表现出较低的光催化活性，不能满足工业应用要求。对ZnO进行改性能够提高ZnO对可见光的利用率及光催化活性。其中,对ZnO进行掺杂能够有效改变光催化剂的比表面积、颗粒大小和光催化活性等性质，适当引入一些金属或非金属离子有可能使催化剂对光的吸收范围扩展到可见光区。金属掺杂能使ZnO形成更多的晶格缺陷，降低电子和空穴的复合几率；而非金属掺杂能够在ZnO晶格中引入氧空位以及引起ZnO晶格膨胀，使ZnO禁带变窄，进而能吸收可见光；同时，掺杂两种非金属有可能比掺杂单一非金属更能改善ZnO对可见光的吸收。结合金属掺杂与非金属掺杂的优点，金属与非金属共同掺杂到ZnO中，使ZnO的各种缺点得到全面改善。此外，利用金属氧化物对ZnO进行掺杂，可改变ZnO晶格结构以及表面电子状态，提高ZnO光催化活性。需加强对掺杂理论的研究,掺杂虽能使ZnO能够吸收可见光，但是对可见光吸收不强，对太阳能利用率不高，需要对ZnO改性方法进行更深入研究,同时，光催化要进一步在工业上进行应用，应加强对光催化降解多组分废水及真实废水进行研究,其稳定性、固载化及其回收利用方面也应该得到更多关注。

Development of doped ZnO photocatalysts

As a semiconductor photocatalyst with the advantages of non-toxic, high efficiency and low cost, ZnO is widely studied. Because the band gap of ZnO is about 3.37 eV, ZnO can only absorb ultravi- olet light, and the light electrons and holes are easily recombined. Under the irradiation of the sunlight, ZnO showed low photocatalytic activity, which could not meet the requirements for commercial applica- tion. Modification of ZnO could improve the utilization of visible light and the photocatalytic activity of ZnO. Element doping could effectively change the specific surface areas, particle sizes, and catalytic activ- ity of ZnO, and appropriate introduction of some metal or nonmetal ions could make the light absorption of ZnO photocatalyst extend to visible region. After doped by metal, much more lattice defects could be pro- duced in ZnO, which could reduce the recombination of electrons and holes. Nonmetal doping could intro- duce the oxygen vacancy in the lattice of ZnO and cause the lattice expansion of ZnO, and narrow the band gap of ZnO,which made ZnO absorb the visible light. Compared with the single nonmetallic doped ZnO, doping with two kinds of nonmetal might further improve its absorption of visible light. The photocat- alytic activity of ZnO was effectively improved by doping metal and nonmetal. Besides, the lattice structure and electronic state of ZnO surface were changed by doping with metal oxides, which improved the photo- catalytic activity of ZnO. After doping with the materials, ZnO can absorb visible light, however, the ab- sorption intensity for the visible light is not strong and the utilization of solar energy is low, which demon- strate that the doping theory of ZnO needs further studying. At the same time, for the further application of photocatalysis in industry, the photo-degradation of multicomponent wastewater and real wastewater should also be investigated, and more attention to the stability, immobilization and recycling of the photocatalyst should be paid.