Novel Photocatalytic Materials Based On Two-Dimensional HNbWO₆ Nanosheets

Energy is the foundation of the national economy and social development.It is also the important material guarantee for human society survival and development.Photocatalytic technology using sunlight directly to drive the chemical reaction has been regarded as an enormous potential way for transforming the low density light energy into the high density chemical energy.Therefore,to develop high efficiency,stable and low-cost semiconductor photocatalysts have become challenging topics in the photocatalytic field.Inorganic two-dimensional nanosheets are a class of nano-materials with molecules or atoms thickness and infinite planar structures.The nanosheets with outstanding properties,such as high specific surface area,anisotropic features,and single crystalline texture,make them as the excellent candidates for catalyst designing and nano-composites building.In this thesis,we focused our study on the development of an efficient,simple method towards the ultrafast synthesis of HNbWO6 monolayer nanosheets with fascinating photocatalytic performance.The visible light performances of these materials were further optimized by the dye sensitization strategy.Based on the flexibility of layered transition metal oxide precursor,we explore the preparation method of uniformly doped monolayer nanosheets and investigation the influence of component on the band structures,light absorption ability and photocatalytic activity.These studies provide useful insights for future rapid preparation of monolayer nanosheets photocatalysts and lay the foundation for profound understanding the intrinsic nature of nanosheets materials from molecule level.The details are summarized briefly as follows:(1)The HNbWO6 monolayer nanosheets were prepared via an ultrafast,simple technology based on an acid-base reaction and ion intercalation assisted exfoliation strategy by using triethanolamine(TEOA)as a stripping agent.Moreover,this process is a common method.Compared with the HNbWO6 nanosheets prepared by the traditional method(using tetra-n-butylammonium hydroxide(TBAOH)aqueous solution as a stripping agent),the ultrathin HNbWO6 nanosheets suspensions obtained by this way showed much higher activity for photocatalytic H2 evolution.(2)A uniform doping strategy has been developed for the fabrication of two-dimensional monolayer HNbxTa1-xWO6 nanosheets solid solutions,which were exfoliated from layered LiNbxTa1-xWO6 solid solutions precursors.The effect of the component on the band structures,optical absorptions and photocatalytic activities can be realized at the molecular level by this strategy.Combining with the photo-electrochemical analyses,the relationship between bandstructures and photocatalytic activities have also been established.(3)A flexible and simple electrostatic self-assembly method has been developed to fabricate novel Ru(bpy)32+/HNbWO6 nanosheets nanocomposites photocatalysts based on the negatively charged of the nanosheets for the first time.Such a method can make the two ingredients undergo a homogenous phase relatively adequate interfacial interaction,leading to the efficient photocatalytic performance for H2 evolution under visible light irradiation.