Study On Modification And Application Of Boron-doped Diamond Films

The electrochemical oxidation method is simple and has no secondary pollution.It has great application prospects in sewage treatment.Boron-Doped Diamond（BDD）has good applications in the field of electrochemical due to its corrosion resistance,stable chemical properties,wide electrochemical potential window,high oxygen evolution potential,low background current,and good reversibility.However,the low catalytic efficiency and high cost of BDD electrodes have limited their large-scale applications.In order to reduce the cost of BDD and improve the catalytic efficiency,it is necessary to find a matching material to improve its performance.In this paper,TiO₂ was selected to modify BDD film electrodes.First,the electrophoretic multiple deposition method was studied to deposit TiO₂ on BDD to improve the morphology and performance;an electrochemical oxidation device with TiO₂/BDD as the electrode was designed,and the conditions for its optimal hydroxyl radical（·OH）generation rate were studied.Secondly,the TiO₂/Au/BDD composite electrode material was designed based on the Z-scheme of photocatalytic,and the effect of Au content on the performance of TiO₂/Au/BDD was studied.Finally,an electroflocculation-electrochemical oxidation device for the treatment of landfill leachate was designed.The treatment effect of the device on landfill leachate was studied.The main research findings are as follows:（1）After the BDD electrode was modified by TiO₂,the electrochemical potential window was widened,which is beneficial to the electrochemical oxidation reaction.When TiO₂ was deposited 3 times（60 s each）at a DC voltage of 40 V,the obtained composite electrode material has the best surface morphology,electrical and electrochemical properties,and its Hall mobility reached 213 cm²/V·s,compared to a single BDD electrode,it is increased by 3.5 times.The electrochemical potential window is 4.6 V,4.3 V,and 4.6 V in alkaline,acidic,and neutral environments,which are wider than the original BDD electrode and have the largest redox peak areas,which means its redox stronger than BDD.（2）A set of flocculation-electrochemical oxidation device was designed with TiO₂/BDD electrode as the core.Different ratios of flocculants have a significant effect on the simulated wastewater treatment effect.When PAM=6 mg/L and PAFC=500 mg/L,the treatment effect on simulated sewage was the best.The·OH production of electrochemical oxidation device is related to Na₂SO₄ concentration,p H,and current density.When the concentration of Na₂SO₄ was 0.1 mol/L,p H=9,and the current density was 100 m A/cm²,The·OH production were the highest.（3）By constructing the Z-scheme TiO₂/Au/BDD system,the performance changes of the electrode TiO₂/Au/BDD relative to the BDD and TiO₂/BDD electrodes were studied.The experimental results show that the TiO₂/Au/BDD sandwich-type three-layer composite structure was obtained,and has good electrochemical performance.The addition of Au was beneficial to improve the performance of the electrode,but it needs a proper amount.Too much Au will narrow the electrode’s electrochemical potential window and reduce the redox property.The simulated wastewater degradation test shows that the TiO₂/Au/BDD electrode has a good photoelectric and photocatalytic effect,which is beneficial to wastewater degradation.（4）Aiming at the characteristics of complex components of landfill leachate and more insolubles,an electro-flocculation and electrochemical oxidation device for the treatment of landfill leachate was designed.The experiments show that the electroflocculation can effectively reduce the chemical oxygen demand（COD）of landfill leachate.In combination with the electrochemical oxidation device,the COD value of the landfill leachate can be reduced by 46.61%within 90 minutes,which has accumulated much experience for the practical application of the TiO₂/Au/BDD electrode in wastewater treatment.