Preparation And Properties Of Boron Doped Diamond Composite Electrode Materials

In this work,Boron-doped Diamond?BDD?powders produced by high temperature and high pressure technology?HPHT?were used as raw material.And then,Al-B-C system sintering aid mixed with Al powders,B powders and C powders in 3:1:3 molar ratio and Ti C sintering aid mixed with Ti and C powders in 1:1 molar ratio were selected and mixed with BDD powders,respectively.The dense Al₃BC₃/BDD composite materials and Ti C/BDD composite materials were prepared by in-situ reaction of high temperature and high pressure technology combined with sintering aid.Technical support is provided for the preparation of composite electrode with strong chemical stability,excellent electrical and electrochemical properties by studying of the effects of raw material formula and sintering process on the phase composition,microstructure,electrical and electrochemical properties.The simulated wastewater degradation experiment was carried out by electrochemical oxidation technology using BDD composite as anode material,and the best wastewater treatment process parameters of two kinds of BDD electrodes were obtained.We independently designed and manufactured a sewage treatment device with BDD composite as electrode material,testing its effect on sewage treatment,and laying a foundation for the wide application of BDD electrode.The research results are as follows:?1?The dense Al₃BC₃/BDD composite materials were prepared by mixing5 wt.%?15 wt.%Al-B-C system sintering aids and BDD powder.Sintering temperature was kept at 1450 ^oC for 300 s and sintering pressure was 5.5 GPa during sintering.The sintering aid reacts in situ during the sintering process to form Al₃BC₃and Al₄C phases,which can promote the densification of BDD.The Al₃BC₃/BDD composite with 10 wt.%sintering aid has the lowest resistivity(4.40×10^-2?·cm)and the highest hole concentration(4.55×10¹⁹ cm^-3).The electrochemical potential windows of this electrode in 0.1 mol/L H₂SO₄,0.1 mol/L Na₂SO₄ and 0.1 mol/L Na OH electrolytes are 1.9 V,2.9 V and 2.3 V,respectively.And the electron transfer coefficient of the composite electrode is close to 0.5,It shows that BDD composite electrodes has good reversibility.?2?The dense Ti C/BDD composite materials were prepared by mixing 10 wt.%to 30 wt.%Ti C sintering aids and BDD powders,respectively.And sintering temperature was kept at 1600 ^oC for 300 s and sintering pressure was 5.5 GPa.The Ti C/BDD composite electrode with 30 wt.%sintering additive has the best electrical and electrochemical properties.The resistivity is 2.44×10^-2?·cm,the hole electrochemical potential windows in 0.1 mol/L H₂SO₄,0.1 mol/L Na₂SO₄ and0.1 mol/L Na OH electrolyte are 3.63 V,2.83 V and 1.91 V,respectively.Meanwhile,it was electrochemically characterized by cyclic voltammetry and found to have good reversibility and electrocatalytic activity.?3?Al₃BC₃/BDD composite electrode and Ti C/BDD composite electrode were selected as anode materials to carry out electrochemical oxidation degradation experiments on methylene blue simulated dye wastewater.The effects of different electrolytes,electrolyte p H,current density and other factors on the treatment efficiency of composite electrode were analyzed.The results show that under alkaline condition,with 3 g/L Na Cl as supporting electrolyte and current density set at80 m A/cm²,Al₃BC₃/BDD composite electrode has the highest treatment efficiency.And methylene blue is completely degraded within 120 min under this condition.With3 g/L Na Cl as supporting electrolyte and current density set at 60 m A/cm²,the Ti C/BDD composite electrode has the highest treatment efficiency and can degrade methylene blue completely in 90 min.?4?In this work,we design and assemble the sewage treatment device with composite electrode as the core,combining with the knowledge of programming control and mechanical design.The device is equipped with power supply unit,obstacle avoidance module,Bluetooth module,electricity monitor,GPS module,electrode module and power module,which can realize the functions of automatic obstacle avoidance,GPS positioning,electricity monitoring,remote control and the most important water purification.Meanwhile,5 L industrial wastewater which chemical oxygen demand?COD?is 5350 mg/L is treated by the device with different core electrodes.The Al₃BC₃/BDD composite electrode and Ti C/BDD composite electrode can degrade 95.1%and 99.6%in 360 min,respectively.