三维多孔Co9S8和Co9S8/石墨烯的拓扑转化制备及其电催化析氧性能的研究

氢能源是一种清洁、高效、可再生的理想能源。电解水制氢是应对能源危机与环境污染的重要手段。电解水反应包括阴极析氢和阳极析氧两个半反应，但析氧反应所需的贵金属催化剂资源稀缺、价格昂贵，是电解水制氢发展的瓶颈之一。镍黄铁矿型Co9S8，具有较好的导电性和催化活性，是一种可替代贵金属的经济、有效的析氧催化剂；但其结构比较复杂，合成相对困难。因此，本项目拟通过拓扑转化法制备三维多孔Co9S8纳米材料及Co9S8/石墨烯纳米复合材料，研究其生长过程和电解水析氧性能，探索反应路径及催化机理，阐明协同作用。三维多孔Co9S8，具有较大的比表面积，更多的活性位点，可改善催化性能。另外，Co9S8原位生长在石墨烯上可提高材料的导电性，扩大两相界面，利于电子在两相间传递，使之具有更优异的催化性能；二者界面的强力结合增强材料的结构和催化稳定性。本项目的顺利进行将对新型、高效、高稳定性析氧催化剂的研究具有重大意义。

Hydrogen, a clean and renewable fuel, has long been considered to be an essential energy source for our future energy landscapes. Electrochemical water splitting for sustainable hydrogen production is a promising and appealing approach to address the global energy issues. However, the sustainable electrocatalytic water splitting process, including cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER), has been largely hampered, mainly because of the expensive and scarce noble metal electrocatalyats for OER, such as Ru and Ir based materials. Hence, developing highly active and robust earth-abundant electrocatalysts to make the water splitting process more energy-efficient and cost-effective is highly desirable. Pentlandite Co9S8, one type of variable Co and S binary compounds, has been proven to be a promising candidate of noble metal OER electrocatalyst, due to its inherent catalytic activity, earth-abundance and cost-effective. However, because of the complexity of Co and S bond, it is difficult to synthesize Co9S8 nanomaterials. In this proposal, three-dimensional (3D) hierarchical porous Co9S8 nanomaterials and Co9S8 in situ grown on graphene nanosheets (Co9S8/graphene) nanocomposite with uniform structure and controllable morphology can be successfully synthesized by the topotactic conversion process and analyzed by the state-of-the-art characterization techniques. The nanomaterials’ growth mechanism will be carefully studied. Moreover, the electrocatalytic performance of the Co9S8 and Co9S8/graphene towards OER in basic electrolyte will be systemically investigated. In addition, the reaction pathway, electrocatalytic mechanism as well as the synergist effect between Co9S8 and graphene will be deeply explored based on both experimental data and the theory calculation analysis. 3D hierarchical porous Co9S8 nanomaterials, synthesized by topotactic conversion process, can provide larger surface area and more exposed active sites in electrolyte, and hence lead to a better electrocatalytic performance. Besides, Co9S8/graphene can improve the materials’ conductivity, enlarge the interface area between 3D Co9S8 and graphene nanosheets, benefit the electron transport between the two phase, and thus give excellent electrocatalytic performance. Additionally, this special interfacial structure can potentially provide the structural and electrocatalytic stability. The successful completion of this project can not only resolve the key problems with water splitting, but also provide a pavement for discovering and investing other novel, efficient and high stability precious-metal-free OER electrocatalyst.