Spontaneous Electrosynthesis Glyoxalic Acid On Nano-structure Electrodes

Organic electrosynthesis has been given great attention by chemists since it is one of green and sustainable development chemical method. The modified electrode based on the nano-TiO₂ film is one kind of new nanometer structure electrode material. The application prospect is very widespread. The nano-TiO₂ film modified electrode has the heterogeneous electrocatalysis function for organic substance reduction. It can electroreduct nitrobenzene, succinic acid, oxalic acid using the nanoTiO₂ film modified electrode . The nanoTiO₂-Pt modified electrode can electrooxidate methyl alcohol, ethyl alcohol , glucose and so on. The nanoTiO₂ film modified electrode has the important scientific value and the technical innovation in the organic electrosynthesis application. Spontaneous organic electrosynthesis using the fuel cell reactor simultaneously obtain the goal product and the electrical energy , not only does not need the external electrical energy but also can provide the electrical energy. It is one kind of new effective green organic electrosynthesis methods. This paper mainly study the glyoxalic acid's spontaneous electrosynthesis reaction. We prepare the nano-structure Ti/nanoTiO₂ film modified electrode and Ti/nanoTiO₂-Pt modified electrode, and investigate their electrocatalytic activity. In the spontaneous electrosynthesis reactor separating by positive ion membrane,we spontaneous electrooxidate oxaldehyde to glyoxalic acid, simultaneously obtain the electrical energy. Concrete research work including the following three parts:Part 1: The nanoTiO₂ film electrode (Ti/nanoTiO₂) and the electrode loaded Pt nanoparticle(Ti/nanoTiO₂-Pt) were prepared by sol-gel method and electrochemical deposition technique. They were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The result showed that the anatase nanoTiO₂ membrane was the porous network structure and the cluster scattered state Pt particles distributed on the surface of the multi-nanoporous TiO₂ film and the average particle size of Pt particles was about 25 nm. The modified electrodes were investigated by cyclic voltammetrys (CVs) in 0.50 mol·L-1 H2SO4. The results showed that the Ti/nanoTiO₂ film electrode had two couples of oxide-reduction peaks, they can be heterogeneous electrocatalytic medium for different organic reductive reaction. The Ti/nanoTiO₂-Pt modified electrode exhibited platinum significant electrochemical activity, and the electrochemical activity of modified electrode was superior to pure Pt electrode.Part 2:1. The electrochemical activity of Ti/nanoTiO₂-Pt modified electrode was investigated in glyoxal and sulfuric acid mixture solution. The results showed that the Ti/nanoTiO₂-Pt modified electrode exhibit significant electrocatalytic activity for the oxidation of glyoxal, the potential of oxidation peaks were 0.538V and 1.084V(vs.SCE) respectively. It was about 2.0 times higher than that of pure Pt electrode. The reaction process was controlled by the concentration polarization.2. In the electrolyzer separating by positive ion membrane ,Ti/nano TiO₂-Pt modified electrode as cathode and the anode respectively, electrooxidate oxaldehyde spontaneous electrosynthesis glyoxalic acid. The anolyte was the oxaldehyde and the sulfuric acid mix solution. The catholyte was the sulfuric acid solution. The catholyte was purged with oxygen. The research result indicated that when the external resistance was 1 ohm. The spontaneous electrosynthesis reactor's greatest voltage may reach 0.582V. The oxaldehyde concentration was 0.4 mol/L. The sulfuric acid concentration was 1mol/L. Both's volume ratio was 1:2. The spontaneous electrosynthesis glyoxalic acid's efficiency was highest.3. Spontaneous electrosynthesis goal product used the ultra-violet spectrograph(UV)and High Performance Liquid Chromatography(HPLC) methods represent. The spontaneous electrosynthesis's product is the glyoxalic acid and High Performance Liquid Chromatography(HPLC) is the highly effective method to analysis glyoxalic acid product. The chromatograph condition as follows: The chromatographic column was Column C18 (5μm, 250×4.6mm), the mobile phase was dilute phosphoric acid solution (PH=2.6) with a flow rate of 0.6ml/min. The ultraviolet examination wave length was 212nm, the chromatograph temperature was the room temperature and sample size was 2μL.