Preparation Of Ti/TiO₂ Film Electrode And Its Electrochemical Properties

Organic electrosynthesis as a green synthesis method has been given great attention by domestic and foreign researchers since it meets the requirement of sustainable development. It is also a development trend of the future synthesis chemistry. The nano-TiO2 film electrode is a kind of new nanometer structure electrode material. Its application prospect is very widespread. The nano-TiO2 film electrode has the heterogeneous electrocatalysis function for organic substance reduction. It can reduce nitrobenzene, succinic acid, oxalic acid using the nano-TiO2 film electrode. The nano-TiO2 film electrode has the important scientific value and the technical innovation in the organic electrosynthesis application.In this paper, Ti/TiO2 film electrodes were prepared by anodic oxidation method (electrolyte:1.0 mol/L sulfuric acid solution, anode:polished Ti electrode, cathode:DSA electrode, oxidation temperature:45℃, oxidation voltage:20 V, oxidation time:2 h). Elemental composition and valence state analysis of anodic oxidation film were characterized by X-ray photoelectron spectroscopy (XPS). The surface morphology of oxidation film was observed by scanning electron microscopy (SEM). The roughness of Ti/TiO2 film electrode was determined by potential steps. The analysis results showed that the surface of anodized electrode had irregular particles with a size of 0.5～1μm and was rougher than that of the polished Ti electrode. The prepared electrode only contains Ti and O two elements, Ti existed as Ti4+ (TiC>2) and other valence states of Ti were not found. Consequently, it can be concluded that the prepared electrode surface is covered by TiO2 film. Anodic oxidation is very useful to produce a greater roughness for the polished Ti electrode which could increase the surface area and the electrochemical properity. The electrocatalytic properties of Ti/TiO2 film electrode towards the electrocatalytic reduction of oxalic acid to glyoxylic acid were evaluated by CV, in situ FTIR and preparative electrolysis experiments. Experimental evidence was presented that Ti/TiO2 film electrode had good heterogeneous electrocatalytic activity for the reduction of oxalic acid and the reduction process was a rapid and irreversible reaction. The mechanism of electrocatalytic reduction of oxalic acid to glyoxylic acid was proposed by CV, XPS and SEM. In this mechanism the TiO2/Ti(OH)3 redox couple as the medium indirectly catalyzed reduction of oxalic acid.In addition, galvanostatic electrolysis experiments of oxalic acid were carried out with Ti/TiO2 film electrode. The results showed that in the undivided cell with Ti/TiO2 film electrode as the cathode, DSA as the anode, under the conditions of temperature 20℃, current density 300 A/m2 and electrolysis time 8h, the conceration and the yield of glyoxylic acid were highest. They are 34.90 g/L and 57.68%, respectively. The yield of gloxylic acid on Ti/TiO2 film electrode is increased by 27.10% compared with that on the polished Ti electrode.