Morphologicallycontrolling Preparation And Properties Of BiVO₄ And Its Composites As Highly Active Photocatalysts

Nowadays photocatalysis has been an extremely important research topic.The developments of photocatalytic water-splitting for hydrogen production from water and photocatalytic degration of organic pollutants,and other important photocatalytic processesaregreatly favored.For decades,researchers have made significant advances in photocatalytic theory and applications.TiO₂ has become the most important photocatalyst in the past decades because of its excellent resistance to chemical and photic corrosion,low cost.In most of the domestic and foreign reports,TiO₂ is modified as different photocatalysts in different applied fields.Although TiO₂ is the most widely studied semiconductor photocatalyst,no major breakthrough in practice applications has been achieved up to date,due to its low catalytic activity.In recent years,researchers have made some significant progress in exploring new photocatalysts.In this disseration,the new visible-light driven catalyst BiVO₄ has been further studied based on the previous researches.The photocatalytic quantum efficiency and the light absorption range of BiVO₄ are further enhanced by means of morphological controlling and combination with other semiconductors.The morphology,morphology,microstructure and spectral properties of the prepared materials were analyzed by field emission scanning electron microscopy?FE-SEM?,X-ray diffraction?XRD?,transmission electron microscopy?TEM?and UV-visible light?TEM?Reflection spectroscopy?UV-vis DRS?,Fourier transform infrared spectroscopy?FTIR?,photoluminescence spectroscopy?PL?,N2 adsorption-desorption isotherms and photoelectrochemical measurements.The main results are as follows:?1?BiPO₄/BiVO₄ composites were prepared by a combined two-step route including hydrothermal and solvothermal synthetic method.FE-SEM and TEM reveale that the as-prepared BiVO₄ exhibites a truncated bipyramid morphology with high {010} {110} exposed facets,and that the as-obtained BiPO₄ nanoparticles are grown on the surface of BiVO₄,leading to the formation of the BiPO₄/BiVO₄ heterojunction.The transient photocurrent-time behaviors indicates that the formed heterojunction made the transfer and the separation of the photo-generated carriers more efficient.The as-synthesized BiPO₄/BiVO₄ composites exhibite high photocatalytic activities in the degradation of rhodamine B under visible-light irradiation.It is found that the sample which is prepared in the BiPO₄/BiVO₄ molar ratio being 3:10 shows the best performance.?2?Under the strategies of the morphology engineering method and the heterojunction construction,In₂O₃/BiVO₄ composites with different molar ratios are prepared through a simple two-step hydro-/solvothermal route.The as-prepared monoclinic BiVO₄ shows a truncated bipyramid shape with high exposed {010}{110} facets,on which the hexagonal In₂O₃ nanoparticlesare grown,leading to the formation of a heterojunction structure.Due to the high-active exposure facets of BiVO₄ and the improved separation efficiency of the photogenerated carriers,which is originated from the formed heterojunction,In₂O₃/BiVO₄ exhibites excellent visible-light photocatalytic activity in the degradation of rhodamine B.?3?Carbon sphere template,with a diameter of about 250 nm,is prepared from the pyrolysis of glucose by a hydrothermal method.BiVO₄ nanoparticles loading on the template with a uniform distribution are synthesized via a solvothermal method.BiVO₄ submicron hollow spheres are successfully obtained after the carbon sphere template removing through two-step calcination at a suitable temperature.The results show that the carbon templatesare uniform in size with smooth surface and good dispersity,and hollow spheres with smaller sizes can be obtained in an ethylene glycol solvent system.The submicron hollow spheres are composed of monoclinic BiVO₄ phase,and its UV-vis absorption spectra show the band gap energy is about 2.34 eV.The photocatalytic activity of the hollow sphere BiVO₄ catalyst is evaluated by using rhodamine B dye as the target pollutant,and it turns out that it behaved good photocatalytic activity under visible light irradiation.Meanwhile,the role of ethylene glycol in solvent system in the aggregation of BiVO₄ is further discussed.