微米级多孔镍合金阴极材料的设计及构效关系研究

Cathode for hydrogen evolution reaction with good electrocatalytic activity is a key material for large-scale and low cost hydrogen production by water electrolysis, which is of great significance for the use and development of hydrogen energy.Through alloying various elements and designing appropriate pore structures, the activity for hydrogen evolution reaction and oxygen resistance of electrodes can be elevated by the synergistic effect between the elements, and the activity center in catalyzed reaction can be increased by increasing the surface area of the materials which is the basic principle of reasonably designing the electrodes. In this project, element powders of Ni, Cr and Fe are used as raw materials as to prepare porous Ni-Cr-Fe alloys with micro-pore structure by means of powder metallurgy technology. The accomplishment of this project will help us to obtain a large-scale and controllable production method for ternary porous electrodes. The purpose of this project is to explore the mechanism of pore formation through calculating the thermodynamics values and discussing the dynamics process during the fabrication reaction and uncover the catalytic mechanism for hydrogen evolution reaction by systematic researching the kinetic parameters and impact factors in electrode process as to disclose the relationship of materials pore structure and electrocatalytic activity, and finally to build up the theory on design the porous catalysis electrodes. This work can help to provide elementary theoretical foundation and new methods for reasonable designing and preparing new electrocatalyst for hydrogen evolution reaction with high activity, low overpotential and good stability.

具有较高催化活性的电解水析氢阴极是实现大规模、低成本制备氢气的关键材料，对氢能源的开发和利用具有重要意义。通过多种元素的合金化，设计适宜的孔结构，既能利用元素间的协同效应提高电极的析氢活性，改善材料的抗氧化性能，又能提高材料的比表面积，增加催化反应的活性中心，是合理设计电极的基本原则。本项目以Ni、Cr、Fe元素粉末为原料，采用粉末冶金方法制备具有微米级孔结构的多孔Ni-Cr-Fe合金电极，获得规模化生产三元多孔电极的可控制备方法。通过计算分析反应中的热力学数值和动力学过程来探究材料的造孔机制, 进行电解水过程中析氢反应的动力学参数和影响因素的系统研究以揭示析氢机理，阐明多孔合金电极材料的孔隙结构与析氢活性之间相互关系，最终形成完整的多孔电极设计理念，为合理设计和制备活性高、过电位低、性能稳定的新型析氢电极提供理论基础。

当前随着世界工业的飞速发展,能源消耗快导致资源短缺及环境污染等问题日趋严重，氢气作为二次能源以其清洁无污染、高效、可储存和方便运输等优点，被视为最为理想的能源载体。在各种制氢技术中，电解水制氢具有产品纯度高、电解效率高、无污染、取材丰富等优点已被广泛利用。镍基多孔材料既利于形成气体通道，又可以提高材料的比表面积，从而增加催化反应的活性中心，是一种高效的析氢电极材料，在航天、航空、能源等领域应用较广泛而受到各界的关注。因此，对镍基多孔材料的研究势在必行。.本课题采用元素粉末反应合成法，利用固相偏扩散的原理进行固相烧结制备了Ni-Cr-Fe、Ni-Fe-Mo、Ni-Fe-Mo-C-LaNi5多孔材料，并研究了Ni-Cr-Fe多孔材料的抗高温氧化性能以及Ni-Cr-Fe、Ni-Fe-Mo、Ni-Fe-Mo-C-LaNi5多孔材料的电催化析氢性能。.研究表明，Ni-Cr-Fe的氧化产物呈细小颗粒并紧密附着于基体，从而阻止了氧化的进一步发生，呈现出优异的抗高温氧化性能。通过采用阴极极化、循环伏安法以及交流阻抗谱对多孔Ni-Cr-Fe、Ni-Fe-Mo、Ni-Fe-Mo-C-LaNi5材料的电催化性能及其析氢稳定性能进行研究。通过在6mol/L KOH的碱性溶液中测量其电化学稳态极化来确定体系的动力学参数。结果表明，多孔Ni-Cr-Fe阴极材料在6 mol/L KOH中具有优异的抗腐蚀性能。在高温条件下其Tafel斜率为-130mVdec-1，室温下的交换电流密度为7x10-4A/ cm-2，通过Arrhenius曲线图计算得出析氢激活能约为21KJ/mol，表明Ni-Cr-Fe电极具有良好的析氢性能；Ni-Fe-Mo多孔电极材料的成分配比为8:1:1，烧结温度为800℃具有良好的析氢性能，室温下的交换电流密度为2.89×10-4 A•cm-2；Ni-Fe-Mo-C-LaNi5多孔复合电极材料的孔隙率为35.1%，平均孔隙约3.7µm，具有丰富的孔隙，该电极电解析氢的反应控制步骤为电化学步骤，交换电流密度约为1.13×10-3 A•cm-2，析氢激活能约为20.75 KJ/mol，Ni-Fe-Mo-C-LaNi5多孔复合电极的本征催化活性只有纯Ni电极的1.5倍左右，而比表面积活性却是纯Ni电极的9倍，表现出优异的电解析氢活性。