Ag掺杂三氧化钨的制备及其光催化降解甲苯性能研究

Preparation of silver-doped WO and study on its photocatalytic performance for degradation of toluene

以钨酸钠与硝酸银为原料,采用水热法将Ag元素引入斜方晶型WO_(3)光催化剂,探究了Ag元素提高WO_(3)光催化活性的机理。光催化降解实验结果表明,当n(Ag)∶n(W)=1∶500时,甲苯的降解效率达到90%以上,与未掺杂Ag的WO_(3)相比,其降解效率提高11.7%;第3次循环时甲苯降解率达到82%,表明Ag/WO_(3)具有较高的稳定性。综合表征结果表明,Ag元素的添加不改变WO_(3)的晶型结构,随着Ag元素掺杂比例的增加,WO_(3)粒径不断减小,禁带宽度由2.23 e V降低为1.72 e V。Ag元素的掺杂增加了WO_(3)中的氧空位,促进了电子-空穴的分离。但当n(Ag)∶n(W)>1∶500时,过多的氧空位形成了新的复合中心,更多的电子被束缚,导致WO_(3)催化活性降低。

Silver is doped into orthorhombic tungsten trioxide(WO_(3))through hydrothermal method with sodium tungstate and silver nitrate as raw materials.Influence of silver doping on the photocatalytic activity of Ag/WO_(3) is investigated.The as-prepared catalysts are characterized to explain the amelioration effect of silver on WO_(3) in detail.Photocatalytic degradation experiment results show the degradation rate of toluene over Ag/WO_(3) exceeds 90%when n(Ag)∶n(W)=1∶500,which is 11.7%higher than that over WO_(3) without Ag doping.The degradation rate of toluene can reach 82%when Ag/WO_(3) is used for the third recycling,indicating a high stability.Comprehensive analysis results show that the addition of silver has not impact on the crystal structure of WO_(3).The particle size of WO_(3) decreases with the increase of Ag doping ratio.Silver doping reduces bandgap energy of WO_(3) from 2.23 e V to 1.72 e V,enhances oxygen vacancies in WO_(3) and promotes separation of electron and hole.However,excessive oxygen vacancies form new recombination centers and affect the separation process of electron-hole negatively when n(Ag)∶n(W)exceeds 1∶500,thus the degradation rate of toluene decreases.