晶面协同TiO_(2)的制备及其可见光催化特性

Preparation of TiO_(2)with crystal facet synergy and its visible light photocatalytic properties

以不同氟化物为晶面控制剂,采用超声辅助-溶胶凝胶法制备{001}和{101}晶面协同的F-TiO_(2),借助XRD、TEM和EDS表征其物相结构、微观形貌和元素组成,通过改变氟化物种类和添加量确定F-TiO_(2)的最佳制备条件,并探讨其可见光催化过程中的主要活性物种及作用机理,研究关键反应参数对F-TiO_(2)光催化活性的影响.结果表明,引入NH_(4)F、NaF和HF可调控TiO_(2)沿{001}、{101}晶面生长,同时F-掺杂能够增大材料的比表面积,制备所得材料的光催化性能均高于纯TiO_(2).但在NaBF_(4)调控下合成的TiO_(2)为锐钛矿/金红石/Na_(3)TiF_(6)三相共存的半导体耦合结构,可见光催化活性显著下降.当NH_(4)F添加量为0.1 g时,材料显示出最强的光催化性能,可见光照射60 min后RhB的降解率为97.24%,矿化率达78.39%.降解反应符合一级反应动力学规律,速率常数为0.1321 min^(-1).通过自由基捕获实验和ESR测试发现,h+、·OH均以关键活性因子参与F-TiO_(2)的可见光催化过程.F-TiO_(2)光催化活性增强主要归因于{001}和{101}晶面的协同作用和表面异质结的形成,其能有效提高光催化反应过程中光生电子空穴对的分离和迁移效率.在可见光照射下,适当增加催化剂投加量,降低RhB初始浓度,控制溶液为中性环境,可显著提高材料的降解速率.

F-TiO_(2)with synergistic{001}and{101}facets were prepared via an ultrasound-assisted sol-gel method using different fluorides as crystalline surface control agents,and its phase structure,microscopic morphology and elemental composition were characterized using XRD,TEM and EDS.The optimal conditions used to prepare F-TiO_(2)were determined by changing the fluoride-type and loading,along with an assessment of the main active species and mechanism of the visible light catalytic process.Finally,the effects of the key reaction parameters on the photocatalytic activity of F-TiO_(2)were investigated.The results show that the introduction of NH_(4)F,NaF and HF can regulate the growth of TiO_(2)along the{001}and{101}crystal facets,while the F–doping can increase the specific surface area of the material and the photocatalytic properties of the as-prepared materials were higher than those of pure TiO_(2).However,TiO_(2)synthesized under the regulation of NaBF_(4)is a semiconductor coupled structure with the coexistence of three phases comprised of anatase/rutile/Na_(3)TiF_(6)and the visible light photocatalytic activity significantly decreased.When 0.1 g of NH_(4)F was added,the resulting material showed the highest photocatalytic performance;the degradation rate of RhB was 97.24%and the mineralization rate reached 78.39%after irradiation with visible light for 60 min.The degradation process conforms to the first-order reaction kinetics equation and the rate constant was 0.1321 min^(–1).Radical capture experiments and ESR tests revealed that both h+and·OH participate in the visible light photocatalytic process of F-TiO_(2)as key active species.The enhanced photocatalytic activity of F-TiO_(2)was mainly attributed to the synergistic effect of the{001}and{101}crystal facets and the formation of surface heterojunctions,which effectively improve the separation and migration efficiency of the photogenerated electron-hole pairs during the photocatalytic reaction.Under visible light irradiation,the degradation rate of the materials can be significantly improved by increasing the catalyst loading,decreasing the initial concentration of RhB and controlling the solution to a neutral environment.