Synthesis And Characterization Of Two Phototcatatlysts With Efficient And Broad Spectrum Photocatalytic Properties Under UV,Visible,and Near-infrared Irradiation

As a technology with handy,environmental and wide application range,photocatalysis provides an ideal method for energy utilization and environmental pollution improvement.However,photocatalytic technology has shown a very bright application prospect and huge economic and social benefits,there still are two mainly limitations of photocatalytic efficiency:（1）light absorption;（2）charge transfer and separation,both of which are intrinsically controlled by the electronic structure,thus the efficient catalytic activity can not be achieved.In this research,a simple one-step hydrothermal method was employed to synthesize P25/（NH₄）_x WO₃ hybrid photocatalystand SnO₂ nanoparticles with adjusted energy band configuration by introduced oxygen vacancies.Herein,we have detailedly and systematically investigated full-spectrum-responsive photoreactivity of the obtained samples.Commercial TiO₂ P25 has two serious problems as a photocatalyst.One is that it can only absorb ultraviolet light which only accounts for less than 5%of total solar radiation.The other problem is low photocatalytic efficiency.Aiming at these problems,we combined with efficient light absorption of（NH₄）_xWO₃ nanorods and P25 high catalytic activity,hybrid nanostructured photocatalysts P25/（NH₄）_xWO₃nanocomposites were successfully synthesized via a simple one-step hydrothermal method,and its structure,chemical composition,chemical state,morphology,optical absorption property photocatalytic degradation of rhodamine B under full spectral light irradiation in detail.Research results indicate that benefiting from the photo-absorption property and the synergistic effect of P25 and（NH₄）_xWO₃,broad spectrum response photocatalytic activities covering UV,visible and near infrared regions on degradation of Rhodamine B have been realized by P25/（NH₄）_xWO₃nanocomposites.Moreover,the surface area of the P25/（NH₄）_x WO₃ nanocomposites increased to three times more than（NH₄）_xWO₃ nanorods when（NH₄）_xWO₃ nanorods was combined with P25.The higher adsorption capacity could lead to the easier and faster photocatalytic degradation process because the photocatalytic reaction is a surface-based process.In addition,as a result of the formation of heterojunction,under the action of electric potential,more effective transfer and separation of the photoinduced carriers between P25 and（NH₄）_xWO₃ interfaces,resulting in markedly improved full-spectrum-responsive photocatalytic activities.This work realizes utmost match of solar energy for the aimed photocatalytic reaction and this result is of significance in the utilization of all solar band energy for efficiently removal of organic dyes,whether UV,visible or near infrared light.For the semiconductor photocatalysts,the p states gives intrinsically smaller slope compared to d states at the extrema,hence the holes in the valence band have much smaller mobility than electrons in the conduction band,which further leads to a lower probability or a smaller population of surface reaching holes than that of electrons under light irradiation.As most photocatalytic activities are controlled by holes involved in oxidizing half reactions,the photocatalytic performance is largely compromised.Furthermore,it should be pointed out that the mobility of holes is intrinsically determined by the valence band（VB）width:the wider the VB,the higher the mobility of holes.Broadening the VB width seems to be a good way to directly change the imbalanced mobility of holes and electrons,which facilitates efficient hole transfer and charge separation.Tin oxide（SnO₂）as an inexpensive,stable and important functional material,it has the potential to be an ideal photocatalyst.However,few applications of SnO₂ have been developed for photocatalytic degradation of water pollution due to the large band gap（Eg=3.6 eV）.Herein,change valence band with anion doping as guiding ideology,we developed SnO₂nanoparticles with adjusted energy band configuration by introduced oxygen vacancies via a one-step hydrothermal process.XPS,ESR and PL unveil the distinct oxygen vacancies concentrations.VB-XPS and the UV-Vis-NIR absorption spectrum reveal that the introduction of oxygen vacancies increased valence band width,resulting in the narrowed bandgap and increased photoabsorption.The obtained SnO₂with a desirable energy band configuration exhibits a superior full-spectrum-response of photocatalytic activity and a higher the value of photocurrent and stability,reusability.These could be attributed to a narrowed bandgap and the broaden valence band width.The narrowed bandgap further contributes to extended light absorption range and the broaden valence band width leads to efficient charge transfer and separation,hence revealing an outstanding full-spectrum-responsive photoreactivity.