Construction Of SnNb₂O₆-based Heterojunction And Their Applications In Visible-light Driven Photocatalysis

As a typical two-dimensional?2D?nanosheet material,due to large specific surface area and flexible electronic structure of SnNb₂O₆?abbreviated as SNO?,it has great potential application prospect in the field of photocatalytic degradation of organic pollutants and water splitting.However,the practical application of SNO is hindered by its low quantum efficiency and high recombination rate of potogenerated electron-hole pairs.In order to make up for the defects of SNO nanosheets,this paper constructed SNO-based heterostructure nanocomposite to promote the separation of photogenerated charges,thus improving the photocatalytic activity.The structure and properties of as-prepared samples were investigated by a series of characterization.Meanwhile,the photocatalytic activity and stability of as-prepared samples were tested,and the possible photocatalytic reaction mechanism was further explored.The specific research content was as follows:1.Novel well-dispersed ultrafine TiO2 nanoparticle/SnNb₂O₆ nanosheet?TiO2/SNO?heterojunctions have been synthesized by a facile hydrothermal method.Ultrafine TiO2 particles with average size of around 9.3 nm were uniformly and tightly attached on the surface of SNO nanosheets with approximately 3.2 nm thickness.The photocatalytic activities of the TiO2/SNO nanocomposite were evaluated for the degradation of rhodamine B?RhB?under visible light irradiation.The TiO2/SNO heterojunctions show significantly promoted photocatalytic activity towards the degradation of RhB compared with the bare TiO2 and SNO,which was about 6.8 and 9.2 times higher than that of TiO2 and SNO.On the basis of radical scavenger experiments,superoxide radicals and hole are suggested to play a critical role in the degradation over TiO2/SNO heterojunctions.2.Novel SrTiO₃/SnNb₂O₆?STO/SNO?0D/2D heterojunctions with an interfacial interaction were constructed by a facile two-step wet chemistry strategy.Different characterization techniques were adopted to investigate the microscopic structures and physicochemical properties of the as-prepared hybrid heterojunctions.The optimal weight percent of STO loading is 20 wt%,generating the highest H2 evolution amount of 17.16?mol,which is 298 and 2 times higher than that of bare STO and SNO.Meanwhile,the cycling experiments reveal that the STO/SNO photocatalyst has excellent stable H2-generation ability.It can be suggested that an interfacial interaction among STO and SNO could result in efficient charge separation and enhanced H2 generation activity,which was confirmed by photoelectrochemical analyses.3.A novel visible-light-driven MoS2/SnNb₂O₆?MoS2/SNO?nanocomposite for photocatalytic H2-evolution was designed and fabricated by a facile and effective method.The characteristics of as-prepared samples such as phase and microstructure were tested by TEM,XPS,and PL characterization.As expected,the obtained MoS2/SNO composites exhibited more-efficient solar energy utilization and superior H2-evolution photocatalytic performance.When MoS2 loading content reach 10%,the H₂-production rate of as-prepared MoS₂/SNO(257.78?mol·h^-1·g^-1)was up to 4.3-fold and 5-fold as high as that of pure SNO and MoS2.At the same time,the cycling experiments reveal that as-prepared photocatalyst has excellent stability and recycling performance.According to the mechanism,it was found that the introduction of MoS2not only improved the visible light absorption of MoS2/SNO nanocomposite photocatalysts but also accelerated the charge separation and transmission.