金属氧化物催化剂氧还原(ORR)和氧析出(OER)电催化机理基础和应用研究

Metal oxides catalysts have been widely studied and applied in the fields of metal-air batteries, fuel cells and so on, nevertheless the fundamental understanding of the mechanism and reaction pathways for ORR and OER of the metal oxides catalysts are quite scarce. Herein, we propose a novel approach to study the mechanism and reaction pathways for ORR and OER of the metal oxides catalysts with the combination of electrochemical methods and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), metal oxides nanoparticles and nanofilms with well-defined facets are synthesized and chosen as the objects. The species of the intermediates and the adsorbed configurations variation along with the change of the applied potentials during the ORR and OER processes on the faceted metal oxides will be studied and analyzed in situ in both alkaline solution and non-aqueous solution systemically to reveal the relationship of the facet plane and the electrocatalytic activity of the metal oxides. Afterwards, the study of the mechanism and reaction pathways of the facet metal oxides catalysts will be conducted in a non-aqueous solution, simulating the real circumstance of the lithium-air batteries. The species of the discharge products, amounts variation along with the discharge process, and the dissolution of the discharge products during charge process will be monitored and studied in situ. Rational reaction pathways and mechanism of the lithium-air batteries during charge and discharge will be deduced. Finally the correlations between facet planes - catalytic activity - cell performances of the lithium-air batteries will be linked closely. This work will not only pave the way for the searching of metal oxides catalysts with cost-effective, high efficiency for lithium-air batteries, but also shed lights on other metal-air batteries and fuel cells.

金属氧化物催化剂已被广泛研究和应用于金属-空气电池、燃料电池等领域，但对其ORR和OER过程的反应途径和机理的基本认识和理解却还很缺乏。本项目提出以具有特定晶面的金属氧化物纳米颗粒或薄膜为研究对象，结合电化学测试技术和壳层隔绝纳米粒子增强拉曼光谱，原位研究金属氧化物催化剂在碱性和非水溶液中ORR和OER过程的中间产物种类、吸附构型等随电位变化的情况，将金属氧化物催化剂的晶面结构-电催化活性有效的关联起来。同时通过在非水溶液中以具有特定晶面的金属氧化物催化剂为模型，模拟研究锂-空气电池充放电过程，检测放电产物类型、含量与电位的关系以及充电过程中放电产物的溶解情况，进而提出合理的锂-空气电池充放电途径和机理。最终将金属氧化物纳米催化剂晶面-电催化活性-锂-空气电池性能相关联，为寻找和发展高效、低廉的锂-空气电池，包括其他金属-空气电池和燃料电池用催化剂提供理论支持和发展指导方向。

制备价格低廉、性能优异的非贵金属ORR/OER电催化剂，并对ORR或OER过程的反应途径和机理的认识与理解是实现金属-空气电池、燃料电池、电解水等领域的重要研究方向。通过自组装、包覆、复合等策略我们发展了一系列的合成具有方法简单、价格低廉、ORR和/或OER性能优异的纳米催化剂的制备方法，包括八面体、立方体和十二面体的Fe3O4纳米单晶和Au纳米单晶粒子、B，N共掺杂有序介孔碳(B, N-OMC)、N掺杂的碳层包覆的α-Fe2O3准立方体、NiCo合金纳米颗粒镶嵌的N掺杂的碳纤维、富含氧空位的同轴电缆结构材料NiCo2O4@CNF-OVs，并对这些电催化剂的形貌、组分、结构和电催化性能进行了系统的表征，总结出非贵金属双功能催化剂性能调控的策略。将以上材料作为阴极催化剂，组装得到了性能优异的金属-空气电池，包括锌-空气电池、锂-空气电池。通过简单的溶剂热反应和热处理，我们可控的合成了具有高OER活性和稳定性的微花结构黑铅铜矿相的Ni6MnO8金属氧化物电催化剂(NMO-MF)。原位在线拉曼光谱测试技术证实了在活化过程中NMO-MF表面形成了大量的NiOOH，而该物质通常被认为是OER反应过程中的活性物质。从而说明了为什么活化后的NMO-MF比未活化的OER活性得到显著增强的原因。此外，我们发展了电化学沉积的方法直接在集流体上生长电催化剂，进而系统研究其ORR/OER，HER电催化性能等，避免了导电剂和粘结剂对电催化性能的影响，以及对原位在线检测中间产物的干扰。进一步的，我们采用原位表面增强拉曼光谱技术(SERS)和旋转圆盘电极(RDE)技术相结合的方法，对粗糙金电极在不同pH值溶液中发生氧还原过程(ORR)产生的中间产物类型进行了系统的研究与分析，探讨了不同pH值溶液中氧还原途径和机理。最后我们将原位在线光谱技术拓展到在锂-硫电池中的应用研究领域，进而指导锂-硫电池的结构优化和合理设计。