The Preparation Of Bismuth Molybdate-based Nano Material For Photocatalysis

With the increase of population and the acceleration of industrialization,various kinds of organic wastewater discharge,which seriously damaged the human health and ecological balance of the earth.Therefore,management and control of water pollution become a major issue to be addressed.Photocatalysis as a promising candidate for water treatment has attracted much attention due to its strong oxidation ability,no secondary pollution,low energy consumption,recycle,a mild reaction conditions and easy operation etc.Currently,the researches of photocatalysis mainly concentrated in two aspects:One is modification of some common broad bandgap semiconductor such as TiO2,SnO2 or ZnO to expand their light response region,and the other is looking for a new semiconductor photocatalyst which can respond to visible light,including some of oxide,sulfide etc.Bismuth molybdate as a kind of bismuth Aurivillius oxide has been attracting much attention due to its unique layered structure,excellent optical property and excellent photocatalytic activity.In this thesis,we aimed to explore the photocatalytic performance of bismuth molybdate by modification to obtain better photocatalytic performance.In our work,we mainly focuse on the design and optimization of bismuth molybdate composite,and found that such design and optimization of bismuth molybdate composite is helpful to improve its photocatalytic performance.The major content is as follows:1.Yolk-shell structure Bi2MoO6 is prepared via a template-free process by optimization of the solvothermal temperature.And the formation process of yolk-shell structure Bi2MoO6 is mainly due to Ostwald ripening proceeding.Compared with Bi2MoO6 nanosheets and nanoparticles,yolk-shell structure exhibits higher photocatalytic degradation rate of 97%in 240 min.Such superior photocatalytic performance is due to the multiple light reflections of yolk-shell structure,which can enhance the absorbance of Bi2MoO6.2.As known,CNT and CS exhibit negative charge after acid-treatment.Hence Bi2MoO6 can nucleate and grow rapidly around the CNT or CS to form crosslinked structure Bi2MoO6-CNT composite and core-shell structure CS@Bi2MoO6 composite in the solvothermal reaction.With the introduction of CNT and CS,Bi2MoO6-CNT and CS@Bi2MoO6 composite exhibit enhancement of photocatalytic performance compared with Bi2MoO6,which is because CNT and CS can increase electron transfer in composite under visible light irradiation.Therein,the optimized Bi2MoO6-CNT composite and CS@Bi2MoO6 composite exhibit degradation rate of 89%and 95%in 120 min for RhB,respectively.3.Yolk-shell structure Bi4-2xMOxO6(x?1)microsphere was optimized by adjusting the proportion of Mo and Bi,and found that such microsphere exhibits an enhancement of photocatalytic performance than Bi2MoO6,which is because defects of Bi2.38Mo0.81O6 can increase electron transfer.Therein,Bi2.38Mo0.81O6 exhibits a degradation rate of 99%for RhB in 120 min.Furthermore,We also designed Bi2.38Mo0.81O6@RGO composite.Due to the superior electronic transfer performance of RGO and the stepwise structure of energy levels of composite,the optimized Bi2.38Mo0.81O6@RGO composite exhibits a degradation rates of 99%for RhB in 80 min.4.The Bi2MoO6-SnO2 and Bi2MoO6-TiO2 heterojunctions were synthesized by the addition of TiO2 and SnO2 in precursor.Afterwards,Bi2MoO6 can nucleate and grow rapidly to form heterojunction due to the presence of TiO2 and SnO2.Bi2MoO6-SnO2 and Bi2MoO6-TiO2 heterojunctions exhibit an enhancement of photocatalytic performance compared with Bi2MoO6,which is due to the stepwise structure of energy levels in Bi2MoO6-SnO2 and Bi2MoO6-TiO2 heterojunction.The optimized Bi2MoO6-SnO2 heterojunction exhibits a degradation rates of 97%for RhB in 150 min and 90%for nitrobenzene in 360 min,respectively.And the optimized Bi2MoO6-TiO2 heterojunction also exhibits a degradation rate of 96%for phenol and 94%for nitrobenzene in 300 min.