| Diamond thin films is a perspective material to be used in electrochemistry and electrochemical engineering due to its excellent electrochemical performance. Potential application such as wastewater treatment, electroanalysis and electrosynthesis and sonoelectrochemistry, have been proposed and are being actively pursued now. The electrochemical properties of boron-doped diamond (BDD) thin film electrodes films and their applications to wastewater treatment have been investigated.Structure, composition and surface morphology of the films were examined using several experimental apparatus, such as XRD, Raman spectroscopy, AFM and FE-SEM et al.; It is shown that high quality of diamond film deposition over a large substrate area is uniform. The grain size of BDD thin films is in the range of 20 – 500 nm. It consists of high concentration of sp3-bonded carbon in bulk. Assessment of nano-scratch resistance of BDD thin films shows a better adhesion to silicon substrate.The BDD thin film electrodes have extremely wide electrochemical window (3V) and low background current, which is observed for water decomposition and much wider than the other two kinds of electrodes, active coating Ti anode (ACT) and Platinum electrode deposited on BDD (BDD/Pt). The electrochemical oxidation of chlorophenols (CPs) on BDD electrodes was investigated systemically by cyclicvoltammetry at different conditions. The experimental results show that all CPs redox are unreversible and different at various pHs. The rate-determining step is mass transfer control. The reactivity of CPs depends on the number and position of chlorine atoms in the aromatic ring. The electrooxidation reactivity of CPs on BDD decreases with increasing of acidity constant. A new electrode with electrocatalysis (BDD/Pt) was obtained by Platinum deposited on BDD substrate using sputter. The electrochemical properties of CPs were also investigated at BDD/Pt and ACT electrode by cyclicvoltammetry.The AC impedance measurements of BDD were finished under wide applied DC polarization region. Experimental results fit well to an electrical model. Impedance studies of BDD electrode confirmed that surface state affects characteristics of electrochemical impedance spectroscopy (eg. Time constant). The flatband potential is about 0.95 V vs. SCE in 1M H2SO4 over a frequency of 1 to 631 Hz. The concentration of boron carriers in the diamond was estimated to be approximately 6.91×1017～2.54×1019cm-3. A new equipment for wastewater treatment was developed, which was suitable for BDD thin film electrodes mentioned above. The electrochemical oxidation of several models wastewater, containing phenol and several chlorophenols, was carried out using our equipment. In particular, the effects of operating factors on current efficiency and pollutant removal were studied, such as electrolyte concentration,voltage,current density,space between anode and cathode,flux,temperature,pH value,additive NaCl and anode material. The electrochemical oxidated mechanism of phenol was explored preliminarily. Examination results show that removal rate of COD is near 100% and current efficiency is over 0.8. In addition, electrochemical wastewater treatment containing heavy metal (Cu, Pb) at BDD film electrode was investigated as well, which removal rate is above 90%.Finally, the performances of BDD were compared with ACT. Experimental results show that the former is far superior to the latter in all examined electrochemical properties. Experiments approved that replacement of BDD by ACT for cathode electrode is feasible and it has little effect on electrochemical process. Electrochemical treatment of wastewater containing aniline compounds with the equipment manifested that the degree of mineralization achievable exceeds 90%, which demonstrates that BDD electrode is promising and potential for electrochemical treatment of wastewater.
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