Preparation Of Electrode Materials With Corrosion Resistance By TiN And Their Application In Energy Fields

With the high rate development of the society, the problems of energy shortage and environment protection become more serious. The consumption of primary energy increases rapidly, consequently, it is in short supply and brings on the soaring price of the petroleum and coal, giving high pressure on environment. Under the conditions of that, the development of new energy has been given attention increasingly, and some regenerative energy develops quickly. Electrochemical technology has the characteristic of environment-friendliness and high efficiency, thus it can satisfy this need, and has been given extensive attention in energy feilds. The electrochemical equipment is the core of the electrochemical technology; furthermore electrode material is the core of the former. Based on the special function of TiN, a new preparation method of nanoscale powder and a series of new electrode materials are invented. They are successfully applied to PEM-water electrolysis, low-temperature fuel cell and desulfurized-seawater recovery system later. Meanwhile, their morphology and structures are analyzed by SEM, TEM, STM, XRD and XPS methods, and electrocatalytic activity and stability are evaluated by electrochemical measurements. As a result, they include:Based on the anti-corrosion and high conductivity of TiN coating, TiN-based IrO₂+ Ta2O5 coating is prepared, which has porous structure, thus has high electrocatalytic activity for hydrogen and oxygen evolution. The service life of this coating has been found longer than traditional Ti-based coating by accelerated life test, which confirms the feasibility of using TiN as the base material of these electrocatalytic electrodes.Based on the anti-corrosion and high conductivity of TiN coating, a surface modification technology of stainless steel bipolar plate by low-temperature-oxidation passive film coated with TiN coating is developed. It has good performance of anti-reduction and anti-oxidation in 30% H2SO4 solution, the current density is less than 10μA·cm² , contact surface resistance is 10 m?.cm², within–0.2 - 1.0 Vvs.SCE. Therefore, it can fully satisfy the need of PEMFC in anti-corrosion, conductivity and long-time stability.Based on the high reaction activity of TiN nano-powder, TiN impregnation-thermal decomposition method is invented, and then IrO_x-TiO₂ nano-powder catalyst is prepared, which can be applied to PEM-water electrolysis. Nascent TiO₂ by TiN-precursor thermal oxidation has super reaction activity. Therefore it is easy to undergo solid-phase chemical reaction. In fact, the reason lies in a formation of TiN thermal decomposition product with rutile crystal structure, produced by a specific oxidation-decomposition condition via impregnating, which can react with H₂IrCl₆ thermal decomposition product easily to form IrO_x-TiO₂ solid solution. PEM-water electrolysis test is carried on and it shows that the cell voltage was 1.6 V at 1A cm-2 and 80℃, with 1.2 mg cm^-2 Ir loading. These indicate that it is probably an ideal method to prepare a water electrolysis catalyst with low-loading and high catalytic activity, by TiN impregnation-thermal decomposition method.Based on TiN impregnation-thermal decomposition method, RuO₂-TiO₂ nano-powder and IrO_x-TiO₂ nano-powder are synthesized, which can be used as supports to prepared Pt/RuO₂-TiO₂ and Pt/IrO_x-TiO₂. These electrocatalysts have been successfully applied to PEMFC later. In terms of polarization curves in 0.5 mol/L H2SO4 solution and cyclic voltammetry curves in 0.5 mol/L H2SO4 + 0.5 mol/L CH3OH solution, these curves show that the loaded Pt has synergetic effect with RuO₂-TiO₂ or IrO_x-TiO₂, which results in an excellent electrocatalytic performance for hydrogen evolution and oxygen evolution and methanol oxidation reaction. At the same time, a preliminary PEMFC test indicates that Pt/RuO₂-TiO₂ has good catalytic activity for oxygen reduction reaction, and it has been proved the better stability than Pt/C by anti-polarization experiment.Based on TiN impregnation-thermal decomposition method, a Ti/ IrO_x-TiO₂/IrO₂ coating electrode with IrO_x-TiO₂ interlayer is prepared and used as collector plate of PEM-water electrolysis. Instead of changing the morphology and composition of the traditional Ti-based IrO₂ electrode by adding IrO_x-TiO₂ interlayer, Ti/ IrO_x-TiO₂/IrO₂ electrode holds the good electrocatalytic performance and greatly improves its service life. The optimum conditions of preparing this electrode are as follows: temperature at 450 oC, Ir/Ti molar ratio in interlayer is 0.6/0.4. The contact surface resistance of collector plate with Ti/IrO_x-TiO₂/IrO₂ coating in PEM-water electrolysis is only 3 mΩ·cm², which indicates an excellent comprehensive performance.Based on TiN impregnation-thermal decomposition method, a Ti/IrO_x-TiO₂ /IrO₂-SnO₂ electrode with IrO_x-TiO₂ interlayer is prepared and applied to the recovery system of sea water flue gas desulfurization by electrolysis seawater. The electrode is of good chloride-evolution selectivity. Potential difference between chloride-evolution and oxygen-evolution is 150±10 mV. When it is used in desulfurized-seawater simulated solution (25℃,265 ml 3.5% NaCl electrolyte,pH 3.5) at 200 mA/cm² current density by electrocatalytic oxidation approach, the removal rate of Na₂SO₃ reaches 90.9% while the removal rate of COD is 82.6% 15 min later. All indicate that desulfurized-seawater recovery system by electrolysis seawater may have an assistant effect during a short time.As mentioned above, this treatise finally realizes innovation in new method, new material and new application. It achieves a series of invention patents, publishes many manuscripts indexed by SCI, and eventually forms a relatively perfect independent intellectual property.