银促进的TiO2光催化降解甲基橙

 采用溶胶-凝胶和水热协同法制备了不同Ag含量的负载型Ag-TiO2样品,这些样品具有较大的比表面积和较小的粒径. 适量负载金属银后的TiO2在紫外及可见光下的光催化活性均得到提高. 银在TiO2上的最佳负载量为0.15%, 过高的负载量反而会降低TiO2光催化降解甲基橙的活性. 由于反应机理的不同,银负载对TiO2可见光下催化活性的提高要明显高于对其紫外光下催化活性的提高. 在可见光照射下,从激发态染料注入到TiO2导带的电子迅速转移到了Ag原子簇, Ag原子簇通过促进电荷分离抑制了电子和染料正离子自由基的复合,从而促进了光催化过程. 研究结果表明,有效地促进电荷分离以及激发态电子和氧气分子的反应是提高染料敏化光催化活性的关键.

Photocatalytic Degradation of Methyl Orange on TiO2 Promoted by Silver

The Ag-TiO_2 photocatalyst was prepared by the sol-gel-hydrothermal method.The obtained powder has high surface area and small crystal size.The photocatalytic activity of Ag-TiO_2 is enhanced by proper silver loading under UV and visible light irradiation.The optimum content of Ag is 0.15%.However,the photocatalytic activity of Ag-TiO_2 decreases with the excessive silver loading.The increment in activity of TiO_2 powder enhanced by Ag under visible light irradiation is higher than that under UV light irradiation because of their different mechanisms.Under visible light irradiation,the photoexcited electrons are injected into the conduction band of TiO_2 from the dye and then transformed to silver clusters rapidly.Ag clusters accelerate the photocatalytic process through promoting the separation of charges and depressing the recombination of electrons with dye radical cations.The results indicate that the key to improving the activity of dye-sensitized TiO_2 system is to efficiently promote the separation of charges and accelerate the reaction of excited electrons and oxygen.