Native oxides and their effect on electrochemical characteristics of ta-C:N films

In this work, transmission Fourier transform infrared spectroscopy (FTIR) has been used to study the native oxides on the nitrogen doped tetrahedral amorphous carbon (ta-C:N) thin films deposited by a filtered cathodic vacuum arc system, and the reactions of the oxides with 0.1M NaOH aqueous solution. The native oxides on ta-C:N films possess the bonds of C=O and C-O, and dissociation bond of -OH as on other carbon materials. The amount of the oxides containing C=O and C-O bonds increases with the sp² C fraction inside the material. The oxides can react with 0.1M NaOH solution effectively to produce soluble salts, and the N-C groups in the films become active for oxygen absorption to produce N=C=O after the reactions. When the applied electrode potential is more negative than a critical negative value, the native oxides increase the electrochemical activity of ta-C:N film electrodes in aqueous sulfuric acid solution.