具有优异光激发NO_(2)气敏性能和MB光催化降解效率的ZnO-MoS_(2)纳米复合材料

ZnO-MoS_(2)nano-composites with excellent light-activated NO_(2)gas sensitivity and MB photocatalytic degradation efficiency

实现对有毒、有害气体的有效监测和对有机污染物的快速降解,对于减少大气污染和水污染所带来的危害至关重要。本研究采用超声复合方法将溶胶凝胶法制备的ZnO和水热法制备的MoS_(2)复合到一起,成功制备了ZnO-MoS_(2)纳米复合材料。采用XRD、SEM、TEM、XPS等手段对材料结构、形貌和表面化学组分进行表征。结果表明,多层片状MoS_(2)均匀负载到了ZnO纳米颗粒当中,复合材料具有较好的结晶性和丰富的表面缺陷。利用紫外-可见(UV-vis)漫反射光谱、光致发光光谱(PL)和表面光电压(SPV)对材料的光电性能进行了测试。结果表明,ZnO与MoS_(2)的复合在提升光利用率的同时,能够促进光生载流子的更有效分离。以NO_(2)作为目标气体的室温紫外光辅助气敏测试表明,本方法制备的ZnO-MoS_(2)气体传感器具有良好的灵敏度、恢复性、稳定性和选择性,可在室温下实现对低浓度NO_(2)的有效响应,MoS_(2)复合量为5wt%的ZnOMoS_(2)传感器对0.47 mg/m^(3)NO_(2)的响应值为19.6%。同时,气敏性能研究还发现空气中O_(2)分子在材料表面的吸附会对传感器的气敏性能产生较大的影响,ZnO-MoS_(2)传感器在无氧条件下对NO_(2)具有更高的气敏响应。此外,在模拟太阳光下进行的光催化降解亚甲基蓝(MB)的实验表明,依靠吸附和光催化降解的共同作用,ZnO-MoS_(2)复合材料能够在40 min内实现水溶液当中较高浓度MB(15 mg/L)的快速清除,MoS_(2)复合量为10wt%的ZnO-MoS_(2)样品的反应速率常数达到了0.032 min^(−1)。对机制的分析表明,MoS_(2)较好的吸附性和复合所导致的光生载流子分离率的提升是ZnO-MoS_(2)复合材料气敏和光催化性能提升的关键。

Effective monitoring of toxic and harmful gases and rapid degradation of organic pollutants are essential to reduce the hazards of air and water pollution.In this study,the MoS_(2)nanosheets prepared by hydrothermal method were coupled into the ZnO nanoparticles prepared by sol-gel method to form ZnO-MoS_(2)nano-composites via a facile ultrasonic chemical route.The structure,morphology and surface chemical component of synthesized materials were characterized by XRD,SEM,TEM and XPS.The characterizations show that multilayer MoS_(2)nanosheets are well dispersed among ZnO nanoparticles,and ZnO-MoS_(2)composites have good crystallinity and abundant surface defects.The photoelectric properties were explored by UV-vis diffuse reflectance spectrum,photoluminescence spectra(PL)and surface photovoltage spectra(SPV).The results reveal that the formation of ZnOMoS_(2)heterostructure improves the utilization of light and promotes the effective separation of photo-carriers.The UV light-activated gas sensitivity test using NO_(2)as the target gas preformed at room temperature saw that the prepared ZnO-MoS_(2)gas sensor exhibited excellent gas sensing properties with good sensitivity,recoverability,stability and selectivity,which could effectively respond to low concentration NO_(2).The response of the optimized ZnO-MoS_(2)sensor with 5wt%MoS_(2)to 0.47 mg/m^(3)NO_(2)reached 19.6%.Meanwhile,the gas sensing performance was found to be greatly influenced by the adsorption of O_(2)molecule on the surface of the materials,and ZnO-MoS_(2)gas sensor possessed much higher gas sensitivity to NO_(2)under oxygen free conditions.In addition,the photocatalytic degradation of methylene blue(MB)under simulated sunlight reveal that the ZnO-MoS_(2)composites can rapidly remove the high concentration of MB(15 mg/L)in aqueous solution within 40 min by combined action of adsorption and photocatalysis,thereinto,the ZnO-MoS_(2)sample with 10wt%MoS_(2)shows a reaction rate constant as high as 0.032 min^(−1).Mechanism analysis shows that the improvement of gas sensing and photocatalytic performance of ZnO-MoS_(2)composites mainly attribute to the better absorbability of MoS_(2)and the promotion of photocarrier separation rate caused by combination.