Doped And Electrochemical Properties Of CVD Diamond Films

As a novel material for electrochemical applications, Boron Doped Diamond (BDD) electrode owns a lot of promising properties such as wide potential window, low background current, chemical inertness, and high resistance of fouling. Thus, BDD electrode has been considered to be interesting and prospective for the destruction of pollutant water.In this work, BDD films were deposited on Niobium (Nb) substrate by hot filament chemical vapor deposition (HFCVD) technique. Diborane (B2H6) was used as the boron resource, Hydrogen (H2) and Methane (CH4) were used as reaction gases. The morphology, quality and phase of BDD film were studied and analyzed by Scanning Electron Microscopy (SEM), Raman Spectrometer and X-ray Diffraction (XRD). The results are obtained as followings:We found an optional deposition condition being substrate temperature T=800℃, CH4/H2volume fraction=1/100,deposition pressure P=3.5kPa. The grain size and quality of diamond films decrease as the ratio of B/C increases. Raman spectroscopy shows that the quality of diamond films is good as the ratio of B/C is less than1/100. When the ratio of B/C is more than2/100, the quality of diamond films deteriorate. XRD spectroscopy illustrates that NbC and Nb2C appear as intermediate layers between the substrate and diamond films.The electrochemical properties of BDD electrodes were studied by the Cyclic Voltammetry (C-V) in lmol/L H2SO4, lmol/L KCl and2mol/L KOH. As the same time, electrochemical Cyclic Voltammetry (C-V) was again applied to analyze the degradation of phenol on BDD electrode in25Mmol/Lphenol and lmol/L H2SO4solution. We concluded that:The Nb/BDD electrode owns a wide potential window (3.8V) and low background current (10-5A/cm2) in acid solution when the volume ratio of B/C is between1/100and2/100, and the potential window became narrower as the increase of the ratio of B/C. The potential window became wider as the PH value of solution decreases. The potential window of Hydrogen-terminated BDD electrodes was wider than that of Oxygen-terminated BDD electrodes.The BDD electrodes with the ratio of B2H6/CH4(3-4)/100work more efficiently in25Mmlol/1phenol and lmol/L H2SO4solution. The potential of the oxidation peak of phenol was1.4V. The current density in CV was great when the ratio of B2H6/CH4is (3-4)/100, but it decreases whenever the ratio of B2H6/CH4increases or decreases.