【作者】 徐海波；

【导师】 王佳；

【作者基本信息】 中国海洋大学 ， 海洋化学工程与技术， 2009， 博士

【摘要】 随着人类社会的不断进步和高速发展,当前能源供应和环境保护问题日益突出。以石油为代表的一次能源消耗急剧增高,一次能源的资源和供应紧张以及由此产生的环境影响压力日益严峻,石油和煤炭价格飞涨,在这样的背景下新能源的发展日益受到重视,一些可再生能源得到了迅速发展。电化学技术具有环境友好和高效的特点,恰恰能满足这一发展需求,因而电化学技术在能源领域的应用得到了广泛重视。电化学技术的核心是电化学装置,而装置的核心是电极材料。本文基于TiN材料的特殊功能,创造性地发明了新的纳米粉体制备方法,发明了一系列新型电极材料,并在质子交换膜（PEM）水电解、低温燃料电池和脱硫海水恢复系统中得到了成功的应用。通过扫描电镜（SEM）、透射电镜（TEM）、扫描隧道显微镜（STM）、χ射线衍射（XRD）和光电子能谱（XPS）分析了形态和结构,基于电化学测试评价了电极材料的电催化性能和稳定性能。主要研究结果有:基于TiN涂层的耐腐蚀性和导电性,制备了TiN基IrO₂+Ta2O5涂层,其具有多孔性结构,以及很高的析氢、析氧电催化活性。强化寿命实验发现该种涂层使用寿命高于传统的Ti基涂层,表明TiN作为此类催化电极的载体是可行的。基于TiN涂层的耐腐蚀性和导电性,开发了低温氧化钝化膜复合TiN的不锈钢双极板表面改性技术。表面改性处理后的不锈钢双极板,在30%硫酸溶液中耐阴极还原和阳极氧化性能,在从阴极电位-0.2Vvs.SCE到阳极电位+1.0 Vvs.SCE范围内,电流密度最大不超过10μA/cm²,面接触电阻为10 m·cm²。因此,从耐腐蚀性、导电性和长期稳定性上可以满足PEMFC的使用要求。基于纳米粉体TiN的高反应活性,发明了TiN浸渍-热分解法,制备IrO_x-TiO₂粉体催化剂,并应用于PEM水电解。TiN前体热氧化生成的新生态TiO₂具有很高的反应活性,易于发生固相化学反应。通过浸渍形成了特殊的氧化分解条件,使得TiN的热分解产物为金红石相结构,这种相结构易于同氯铱酸的热分解产物形成IrO_x-TiO₂固溶体。PEM水电解测试表明,在铱担载量为1.2mgcm-2,电解温度80℃,工作电流密度1Acm-2下,槽压为1.6V。说明TiN浸渍-热分解法是制备低载量、高催化性能的水电解催化剂的理想方法。基于TiN浸渍-热分解法,合成了RuO₂-TiO₂纳米粉体和IrO_x-TiO₂纳米粉体,并以其为载体制备Pt/RuO₂-TiO₂和Pt/IrO_x-TiO₂,并应用于PEMFC。在0.5 mol/L H2SO4溶液中的极化曲线和在0.5 mol/L H₂SO₄ + 0.5 mol/L CH3OH溶液中的循环伏安曲线测试发现担载Pt与RuO₂-TiO₂、IrO_x-TiO₂具有协同作用,因而具有优异的对析氢、析氧和甲醇氧化反应的电催化性能。质子交换膜燃料电池测试初步表明Pt/RuO₂-TiO₂具有高的氧阴极还原反应催化活性,进一步的反极实验证明其具有比Pt/C更好的稳定性。基于TiN浸渍-热分解法,制备含有IrO_x-TiO₂中间层的Ti/ IrO_x-TiO₂/IrO₂涂层电极,并应用于PEM水电解集流板。IrO_x-TiO₂中间层的加入没有改变传统的钛基氧化铱电极的形貌特征和组成,并使电极具有相同的电催化响应特性,同时大大提高了钛基氧化铱电极的使用寿命。制备该电极的最优条件:焙烧温度为450 oC,中间层Ir/Ti摩尔比为0.6/0.4。经过实际应用表明,以Ti/IrO_x-TiO₂/IrO₂为涂层的PEM水电解集流板面接触电阻只有3 m·cm²,具有优异的综合性能。基于TiN浸渍-热分解法,制备了IrO_x-TiO₂为中间层的Ti/TiO₂-IrO_x/IrO₂-SnO₂电极,并应用于电解海水恢复系统。该电极具有较好的析氯选择特性,“氯氧差”为150±10 mV。使用该电极在电解条件为pH 3.5,NaCl 3.5%,电解液量265 ml,25℃,电流密度200 mA/cm²的条件下,电催化氧化脱硫海水模拟液5 min后Na₂SO₃去除率为41.9%,COD去除率为32.7%;电催化氧化15 min后Na₂SO₃去除率可达90.9%,COD去除率为82.6%。由此表明电解海水恢复系统在短时间内可以起到对脱硫海水的辅助恢复能力。基于上述内容,本论文最终在创新成果上实现了新方法,新材料和新应用,获得了一系列的发明专利,发表了多篇被SCI收入的论文,形成了较为完善的自有知识产权。更多还原

【Abstract】 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.更多还原