Study On The Electrocatalytic Oxidation Of Formic Acid At The Electrode Modified With Contained-Nd Prussian Blue Analogue

Direct formic acid fuel cell (DFAFC) is a new energy installations, formic acid is adopted as its anode fuel and converted into electric energy by reacting on the electrode.DFAFC have a lot of advantages, such as the simple structure, high efficiency and high convenience of adding fuel, etc. Anode catalyst has great impact on the oxidation efficiency of formic acid and the durable property of the fuel cell in DFAFC. Therefore, looking for the catalyst possessed high catalytic activity becomes a very important research topic.For the above reasons, based on contained-Nd Prussian blue analoge modified electrode, we prepared several multiple mixture modified electrodes complexed Pt particles and polyaniline. These newly modified electrodes were all possessed high catalytic activity, better tolerance to toxic intermediate contamination, and high stability to the electrocatalytic oxidation of formic acid. These electrodes will have excellent application and research value as anode catalyst of DFAFC.There were four chapters in this paper:Chapter one: This section mainly introduced the chemically modified electrode, the polynuclear transition metal hexacyanoferrates modified electrode, the preparation and application of polynuclear transition metal hexacyanoferrates modified electrode. The development and problems existed in DFAFC were introduced in brief, the kinds of organic conductive polymers, which acted as carrier of anode catalyst in DFAFC were also discussed. The structure and properties of polyaniline were described in detail.Chapter two: Nd-Fe-WO₄^2- cyanide-bridged mixed complexes modified platinum electrode was successfully prepared by using electrodeposition method for the first time. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to characterize the morphology and crystalline lattice structure of the modified materials. Formic acid electrocatalytic oxidation behavior on this modified electrode was evaluated by means of cyclic voltammetry and chronoamperometry. The results indicated that the electrocatalytic oxidation current density of formic acid on modified electrode was about 10 times more than on bare Pt electrode,and CV anodic limit potential had significant effect on peak figuration of absorption intermediate in the reverse scan. Moreover, the influence of H⁺ and SO₄^2- concentration in electrolyte solution on the voltammetric characteristics of formic acid electrocatalytic oxidation was also studied, it showed that the peak potential increased with increasing H⁺ concentration, however, decreased with increasing SO₄^2- concentration, but being coexistence of H⁺ and SO₄^2-, the effect of H⁺ played a dominant role. This phenomenon revealed that the rate-determining step of electrocatalytic oxidation of formic acid on modified electrode was correlative with deprotonation process, and the adsorption of SO₄^2-/HSO₄^- would promote the forward oxidation reaction. These conclusions provided new experimental evidences for explaining the mechanism of formic acid electrocatalytic oxidation. Meanwhile, the electrode stability experiments as well as chronoamperometry also demonstrated that the newly developed modified electrode possessed much better electrocatalytic activity and tolerance to toxic intermediate contamination.Chapter three: Based on Nd-Fe-WO₄^2- cyanide-bridged mixed complexes modified platinum electrode, the new Pt/Nd-Fe-WO₄^2-/Pt modified electrode was prepared by means of electrodeposition. The morphology of this modified electrode was characterized by SEM. The effect factors of formic electrocatalytic oxidationon, such as deposition potential, deposition time, the concentration of H2PtCl6 and quiet time were investigated. Formic acid electrocatalytic oxidation behavior on this modified electrode was evaluated by means of cyclic voltammetry and chronoamperometry. The results indicated that the electrocatalytic oxidation current density of formic acid on the modified electrode was about 10 times more than that on Nd-Fe-WO₄^2-/Pt electrode, and when the scan rate was between 50 mV/s and 450 mV/s, oxidation current density of formic acid and the root of scan rate showed good linear relationship. Furthermore, the effect of anode limit in the reverse scan on formic acid electrocatalytic oxidation was also studied. When the anode limit was lower, the oxidation reaction of toxic intermediate was suppressed, it was not conducive to the oxidation reaction of formic acid.Chapter four : PAn-Pt/ Nd-Fe-WO₄^2-/Pt modified electrode was successfully prepared by using electrochemical method, SEM was employed to characterize the morphology of electrode, formic acid electrocatalytic oxidation behavior on this modified electrode was evaluated by means of cyclic voltammetry and chronoamperometry. The results indicated that the reaction of formic acid on this modified electrode was closed related to temperature, the electrocatalytic oxidation current density and temperature showed good linear relationship between the range of 25⁴0℃and 45⁵5℃,and the temperature coefficient of low temperature area was about 4 times more than that in high temperature area. The good linearity between square root of scan rate and current density of formic acid electrocatalytic oxidation indicated that formic acid oxidation on the modified electrode was controlled by diffusion. The reduction peak of PtO and CO2 increased with increasing anode limit in the reverse scan at CV of formic acid electrocatalytic oxidation. Moreover, the catalytic activity, stability and tolerance to toxic intermediate contamination of the newly complex electrode, which composed with inorganic polymer Nd-Fe-WO₄^2- membrane, organic conductive polymer polyaniline film and platinum particles, were the same as Pt/ Nd-Fe-WO₄^2-/Pt electrode, so we could conclude that the Inorganic polymer Nd-Fe-WO₄^2- film also showed excellent voltammetry property.