【作者】 赵君；

【导师】 邓意达； 吴晟；

【作者基本信息】 天津大学 ， 材料工程， 2018， 硕士

【摘要】 氧反应（OER/ORR）催化在金属-空气电池等新能源器件中有着举足轻重的作用。近期,双功能氧催化剂逐渐受到研究者们关注。Pt、RuO₂和IrO₂等贵金属基催化剂被认为是催化氧反应的最佳催化剂,但是由于成本较高,循环稳定性产等因素制约了其进一步发展。所以制备高活性、稳定性的可替代贵金属的氧催化剂是很有价值的研究。镍钴氧是一种尖晶石型的过渡金属氧化物,其二维结构可以为催化反应提供较大的反应面积和较多的活性位点,并且在微观晶体结构中具有两种氧间隙和多种金属离子氧化态。因此制备二维形貌的镍钴氧材料,进而优化表面的活性位点数量,提高电催化性能是很有意义的工作。（1）通过共沉淀-烧结两步法制备镍钴氧化物纳米六方片材料,通过调控烧结温度,在250℃下成功制备出了低含量Co³⁺/Co²⁺和高含量Ni³⁺/Ni²⁺表面,450℃下高含量Co³⁺/Co²⁺和低含量Ni³⁺/Ni²⁺,以及中间状态350℃下的材料。分别对三种纳米材料进行了OER和ORR电化学测试,探究不同金属离子活性位点对电催化性能的影响。其中具有低含量Co³⁺/Co²⁺和高含量Ni³⁺/Ni²⁺表面的样品具有最优的双功能电催化性能,相比于贵金属催化剂Pt/C和RuO₂,制备催化剂具有更好地稳定性。因为富集的Ni³⁺和Co²⁺离子为OER/ORR提供了更多的活性位点,这优化了氧分子的吸附/解吸能垒,从而加速了整体反应动力学。其次,在催化过程中比较大的电导率确保了有效的电子转移。第三,2D纳米片和多孔结构提供了更大的比表面积,这有利于氧分子的吸附和电解质的扩散。（2）通过一步水热法制备了类石墨烯状镍钴氧纳米薄膜材料,在碱性条件下研究了不同Ni掺杂量对OER/ORR电催化性能的影响,测试结果发现当Ni/Co比为1/1时,具有最好的双功能催化性能,在该比例下,Ni和Co元素达到了最优配比,同时薄膜状的特殊结构也为催化提供了有利条件。在模拟现实条件下对基于最优双功能电催化性能的样品的锌–空气电池进行了测试,循环充放电时间可以超过60 h,具有比较稳定的循环充放电性能。更多还原

【Abstract】 Oxygen reaction（OER/ORR）plays a pivotal role in application of the new energy devices such as metal-air batteries.Recently,bifunctional oxygen catalysts have received extensive attention.Pt,RuO₂ and IrO₂ are considered to be the best catalysts for the catalytic oxygen reaction,but their further development is obstructed by several factors such as higher cost and poor cycle stability.Therefore,preparaing highly active,stable catalysts that can replace precious metals is a valuable research.Nickel-cobalt oxide is a spinel-type transition metal oxide.Its two-dimensional structure can provide a large reaction area and more active sites for catalytic reactions,besides,there are two oxygen gaps in its microscopic crystal structure and a variety of metal ion oxidation states.Therefore,it is very meaningful to prepare two-dimensional nickel-cobalt oxide material to optimize the number of active sites on the surface and improve the electrocatalytic performance.（1）A shape-control of hexagon nickel cobalt oxide spinel nanosheets was prepared via co-precipitation and sintering process and the atomic ratio of Ni and Co in raw materials was 0/1 in Co₃O₄ or 1/4.Through simply tuning annealing temperature,different Ni³⁺/Ni²⁺and Co³⁺/Co²⁺atomic configurations on nickel cobalt oxide surface were controllably synthesized.In detail,the oxide treated at250°C has highest value of Ni³⁺/Ni²⁺sites and lowest value of Co³⁺/Co²⁺sites and the oxide treated at 450°C has lowest value of Ni³⁺/Ni²⁺sites and highest value of Co³⁺/Co²⁺sites.Electrochemical results show that the oxide with highest value of Ni³⁺/Ni²⁺sites and lowest value of Co³⁺/Co²⁺sites own the best bifunctional electrocatalytic performance.Besides,it has a longer stable catalytic performance,comparing to RuO₂ and Pt/C.Overall,the remarkable electrocatalytic activity can be ascribed to the following reasons.First,the enriched Ni³⁺and Co²⁺species provide more active sites for OER/ORR,which optimizes the adsorption/desorption energy barrier of molecular oxygen,so accelerating the overall reaction kinetics.Second,the considerable electrical conductivity ensures the efficient electron transfer during the catalytic process.Third,the 2D nanosheets and pore structure offer larger specific surface area,which facilitates the diffusion of oxygen and electrolyte.（2）The graphene-like nickel-cobalt oxide nanofilm was prepared by a one-step hydrothermal method.The effect of different Ni doping amounts on OER/ORR electrocatalytic performance was studied on alkaline conditions.The test results showed that when the atomic ratio of Ni/Co is 1/1 has the best bifunctional catalytic performance.At this Ni/Co ratio,the nickel-cobalt element achieves the optimal ratio,and the special structure of the film also provides a powerful condition for catalysis.The Zn-air battery was tested under simulated reality conditions.The Zn-air battery cycling charge and discharge can work exceed 60 h,showing its relatively stable cycle charge and discharge performance.更多还原