Synthesis Of CuCrO₂ And Its Photocatalytic Performance

With the rapid development of the social economy,the consumption of fossil fuels has increased rapidly,and the energy and environmental problems brought about by this have become increasingly serious.It is extremely urgent to find new and energetic energy sources to replace fossil fuels.Hydrogen energy is a new type of energy with great development potential in the future.The use of solar photocatalytic decomposition of water to produce hydrogen is one of the ideal hydrogen production methods.CuCrO₂ is a copper-iron-bearing semiconductor material with p-type conductivity,can sense visible light,and has a wide range of applications.It has theoretical and practical value for its preparation and modification.In this thesis,chromium nitrate and copper nitrate were used as raw materials,citric acid as complex,ammonia as p H adjuster for solution,and ethylene glycol as auxiliary.CuCrO₂ was synthesized by sol-gel method.The sample was characterized by scanning electron microscopy（SEM）,ultraviolet-visible diffuse reflectance（UV-Vis DR）and X-ray diffraction（XRD）,and p-n composite catalyst was prepared by mechanically grinding of CuCrO₂ and semiconductor oxide WO₃ with n-type conductivity properties.The hydrogen production activity of the composite catalyst for photocatalytic decomposition of pure water was tested.The molar ratio of citric acid to total metal ions,the amount of ammonia added,the addition of ethylene glycol,and the calcination temperature and time of the precursor were investigated for the properties of CuCrO₂ samples.The results showed that the molar ratio of citric acid to total metal ions was 1.7:1,the amount of ammonia water added was 7 m L,the molar ratio of ethylene glycol to citric acid was 1:1,and the obtained precursor was treated at 500℃for 3 h in air atmosphere.The CuCrO₂ sample obtained by calcination at 800℃for 3 h and then calcined at 850℃for 3 h in nitrogen atmosphere has good crystal integrity,small particle size,uniform distribution and good dispersion.The corresponding CuCrO₂-WO₃ exhibited highest photocatalytic properties.Based on the above-mentioned suitable synthesis conditions,CuCrO₂ was modified from the stoichiometric ratio and metal ion doping by sol-gel method.Cu_1-xCr O₂,CuCr_1-xO₂,CuCr_1-xNi_xO₂ and CuCr_1-xCo_xO₂ were prepared（x=0.01～0.05）series of samples,the hydrogen production activity of the composite catalyst obtained by the combination of the above samples and WO₃ was investigated.The results showed that the deviation from stoichiometric modification and Ni²⁺ion and Co²⁺ion doping modification could increase the photocatalytic activity of the corresponding composite catalyst within a certain range,however,the deviation from the stoichiometric ratio was too high,or the concentration of doped Ni²⁺ion and Co²⁺ion was too high,which would lead to a significant decrease in the activity of the sample,using the defect theory and XRD results,the reasons for the change of sample activity were discussed.