Preparation Of BiOI-based Photocatalyst And Study On Photocatalytic Performance

Bismuth iodide oxide（Bi OI）is a stable,non-toxic,corrosion-resistant,new type of chemical photocatalytic semiconductor layered material that absorbs visible light.It has received extensive attention in the fields of energy conversion and environmental improvement.Due to the narrow band gap of Bi OI,there are problems such as easy recombination of photogenerated carriers in practical applications.The main research contents of this study are as follows:（1）The（001）and（010）crystallographically exposed Bi OIs（named B001 and B010,respectively）were prepared by the hydrothermal method by adjusting the p H value.The selected area electron diffraction results show that the crystallographic plane exposed by Bi OI at p H value is 2 is the（001）facet.HRTEM results show that the crystallographic plane exposed by Bi OI is（010）facet when the p H value is 6.The results of photocatalytic reduction of CO₂ show that the B001 sample has a higher CO₂reduction efficiency compared with the B010 sample,and the CO yields of the B001and B010 samples are about 2.5μmol·g^-1·h^-1 and 1.2μmol·g^-1·h^-1.The electrochemical results show that the B001 sample has a smaller electrochemical impedance,a larger current density and a more negative conduction band potential.Time-resolved fluorescence spectroscopy shows that the B001 sample has a higher lifetime of photogenerated carriers.The CO₂ adsorption-desorption isotherm shows that the B001sample is more conducive to CO₂ adsorption than the B010 sample.The theoretical calculation results show that the polarization dipole moment in the c-axis direction of the（001）exposed surface of Bi OI is significantly smaller than that of the（010）exposed surface of Bi OI in the b-axis direction,which is favorable for the separation of photogenerated carriers.（2）The B001/CN sample and B010/CN sample（CN is C₃N₅）were prepared by hydrothermal method.HRTEM results show that when the p H value is 2 the exposed crystallographic plane of Bi OI in the B001/CN sample is（001）facet,and when the p H value is 6 the exposed crystallographic plane of Bi OI in the B010/CN sample is（010）facet.After photocatalytic degradation of methyl orange for 75 min,the degradation rates of B001,B010,CN,B001/CN,and B010/CN samples reached 73.5%,74%,65%,95%,and 97%,respectively.In addition,the B010/CN sample also exhibits high-efficiency hydrogen evolution performance.In addition,the B010/CN sample also exhibited efficient hydrogen evolution performance with a hydrogen evolution yield of about 15μmol·g^-1·h^-1.The electrochemical results show that,compared with other samples,the B010/CN sample exhibits a smaller electrochemical impedance,and the B010/CN sample has a smaller Tafel slope.DFT calculations show that the photogenerated electrons in the B010/CN sample are mainly transferred to the B010sample,and the holes are mainly transferred to the CN sample.Therefore,the construction of B010/CN sample by B010 and CN improves the separation efficiency of photogenerated electron-hole pairs.