| The formation of Z-scheme photocatalytic systems that mimic natural photosynthesis is a promising strategy to improve photocatalytic activity that is superior to single component photocatalysts.However,further application was severely limited due to low light utilization efficiency,rapid electron–hole recombination and serious photocorrosion.The search for low-cost,earth-abundant and environmentally friendly photocatalysts that can efficiently function over the entire UV–vis–NIR spectrum remains one of the most pressing challenges in the photocatalytic elimination of pollutants from water.Herein,we accurately designed and fabricated a direct Z-scheme carbon nanodots/WO3 nanorods composite（CDots/WO3）with highly enhanced photo-response and broad-spectrum photocatalytic activity.Under ultraviolet,visible,near-infrared（UV,Vis,NIR）irradiation,respectively,the removal efficiencies of rhodamine B（RhB）always decreased in the order CDots/WO3（97.1,99.1,61.2%）>prepared WO3 nanorods（66.6,69.1,22.4%）>commercial WO3nanoparticles（22.1,11.6,0%）.Additionally,reaction rate constants of 0.4030 and0.2889 h-1 were achieved by the CDots/WO3 nanocomposites when photo-oxidizing tetracycline hydrochloride（TCH）and phenol,respectively,both of which were2.9times higher than those for WO3 nanorods.This excellent photocatalytic performance was ascribed to synergistic effects,including the highly dispersed carbon nanodots on the surface of the WO3 nanorods and efficient charge separation induced by the heterostructure formed between carbon nanodots and WO3 nanorods.Accordingly,a direct Z-scheme photocatalystic mechanism was proposed to account for the photocatalytic reaction process.The prepared catalyst showed no obvious change in its photocatalytic performance or other chemical properties after 5 cycles of use.As a representative artificial photosynthetic system,direct Z-scheme WO3/CdS is a promising photocatalyst system for water purification.However,this system is still limited due to low electron transfer efficiency and serious photocorrosion.Herein,we designed and precisely fabricated a novel all-solid-state Z-scheme WO3/CDots/CdS system.The CDots,as a non-metallic electron mediator,could promote interfacial charge carrier separation and eliminate photocorrosion with enhanced photocatalytic activity.The phase,morphologies,microstructures,optical and electrical properties of as-obtained Z-scheme WO3/CDots/CdS heterojunction were investigated in detail.The photocatalytic performances of as-prepared catalysts were evaluated by the decomposition of 4-chlorophenol（4-CP）,RhB and TCH,and the reduction of aqueous Cr（VI）in visible light,respectively.The optimized Z-scheme WO3/CDots/CdS-2 photocatalyst exhibited the highest photocatalytic activities for degrading and mineralizing the 4-CP（70.0%and 48.3%in 7h）,respectively,both which exceeded the rates observed in WO3/CdS samples by2 times under the same conditions.In addition,the WO3/CDots/CdS-2 showed an excellent stability and reusability with negligible change at2.2%difference for 4-CP degradation in eight cycles.The release percentage of SO42–(transformed from S2–)and Cd2+were only0.77%and 0.79%when compared with the initial concentration,respectively,which were far less than WO3/CdS system（5.64%and 5.70%）.The results indicated that a thorough and complete Z-scheme charge carrier transfer route was achieved.The toxicity assessment authenticated good biocompatibility and low cytotoxicity of WO3/CDots/CdS.Here,for the first time,we synthesized UV-,visible-and NIR-light-driven direct Z-scheme CDots/WO3 nanorods composite photocatalysts,ensuring the fast interior transport,surface separation and effective solar-light absorption of the carriers so as to enhance the photocatalytic activity.In addition,we designed and precisely constructed a novel all-solid-state Z-scheme WO3/CDots/CdS system,in which CDots were used as a solid-state nonmetallic electron mediator to promote interfacial charge carrier separation and transport and to eliminate photocorrosion in order to enhance photocatalytic activity.This work provided a new strategy for the application of CDots in the preparation of Z-scheme heterojunction. |
