分级微/纳结构ZnO的制备及其光催化性能

分别采用溶剂热法和草酸盐法制得具有分级微/纳结构但形貌迥异的两种ZnO材料,以亚甲基蓝溶液(MB)作为目标降解物对其光催化性能进行评价。结果表明:溶剂热法所制得的ZnO呈花状微球形貌,由纳米片自组装而成;草酸盐法所制得的ZnO为微米棒状形貌,以纳米颗粒为基本单元发展而来。草酸盐法ZnO材料具有更为优异的光催化性能,其对亚甲基蓝溶液的降解反应速率常数是溶剂热法ZnO材料的7.65倍。活性自由基物种鉴定结果证实,两种ZnO材料在受到紫外光激发时均能产生·OH和·O₂^-活性自由基。两种ZnO样品光催化性能的差别源于能带结构不同所引起的活性自由基生成数量上的差异。较之溶剂热法ZnO,草酸盐法ZnO在受紫外光激发时产生的·OH和·O₂^-数量更多,且以强氧化能力的·OH为主,因而表现出更为优异的光催化性能。

Preparation of ZnO with micro/nano hierarchical structure and its photocatalytic performances

Two different morphological ZnO materials with hierarchical micro/nano structures were fabricated through solvothermal method and oxalate method,respectively.Their photocatalytic performances were evaluated by using the degradation of methylene blue(MB)solution as model reaction.The results show that the product via solvothermal method exhibits flower-like micro-spherical appearance assembled by many nano-flakes,while its counterpart derived from oxalate strategy shows micro-rod like morphology constructed by many nanoparticles.ZnO fabricated by oxalate method has much better photocatalytic activity towards MB degradation,whose reaction rate constant is 7.65 times as high as that one obtained by solvothermal method.The identification results for active radicals verify that·OH and·O₂^- are both formed in the two samples when they are irradiated under ultraviolet light.However,due to their diverse band structures,there is difference in number of active radicals produced in the reaction system,which can further lead to different photocatalytic efficiency for MB degradation.As for oxalate-derived ZnO,greater number of·OH and·O₂^- can be formed under the irradiation of ultraviolet light.Meanwhile,·OH with strong oxidation capacity plays a dominant role in the photocatalytic reaction system.As a result,it possesses more excellent property in degradation of MB than that of ZnO originated from solvothermal method.