氮掺杂分级多孔炭担载四氧化三钴的制备及其氧还原和氧析出性能研究

发布时间：2018-05-24 09:43

  本文选题：氧还原反应 + 氧析出反应　； 参考：《北京化工大学》2017年硕士论文

【摘要】：锌-空气电池具有比能量高、容量大、成本低等优点,在储能和电动汽车等领域具有良好的应用前景。锌-空气电池的核心材料是兼具氧还原(ORR)和氧析出(OER)活性的双功能催化剂,目前多采用贵金属(如Pt,RuO2和IrO2等),但受制于成本高昂和储量有限,阻碍了锌-空气电池的商业化。因此,研究开发高效的非贵金属双功能催化剂具有重要意义。本文将具有微观有序多级结构的生物质牛骨进行碳化,制备了原位氮掺杂分级多孔炭(NHPC)材料,以NHPC为载体担载四氧化三钴(Co3O4)纳米粒子,制备了 Co3O4/NHPC双功能催化剂,研究了 Co3O4/NHPC催化剂制备条件、组成结构对ORR和OER电催化性能的影响规律。首先,以牛骨为前驱体,采用KOH为活化剂,通过预碳化-碳化活化制备了高表面积且微孔-介孔-大孔三维连通的NHPC。研究发现,当KOH与预碳化产物质量比为0.4时,制备的NHPC比表面积最大(2047 m2g-1),氮掺杂量为3.85%。在此基础上,以NHPC为载体担载Co3O4纳米粒子,采用油浴水热法制备了 Co3O4/NHPC复合催化剂。NHPC的超高比表面积和表面氮掺杂有利于促进Co3O4纳米粒子高度分散。当油浴温度80℃,氨水加入量1mL时,Co3O4纳米粒子均匀地分散在炭载体上,其平均粒径为7.2 nm,明显小于商业Vulcan XC-72和BP2000炭材料担载制备的催化剂。该催化剂同时保有了NHPC三维连通的孔道结构,比表面积高达1070 m2g-1,氮含量为4.93 wt.%。其次,将制备的Co3O4/NHPC作为ORR和OER双功能催化剂,揭示了电催化性能促进机制。研究表明,Co3O4/NHPC催化剂的ORR催化活性和稳定性均显著优于商业Pt/C,其半波电位为0.835 V(比商业Pt/C高12 mV),0.8 V的动力学电流密度为15.85 mAcm-2(为商业Pt/C的3.76倍),经10000 s恒电位计时电流测试后电流仅下降9.3%。OER性能测试表明,该催化剂在电流密度为10 mAcm-2时的电位为1.65 V,比商业RuO2高10 mV,经10000 s恒电位计时电流测试后电流仅下降8.2%,表现出优于商业RuO2的OER催化活性和稳定性。Co3O4/NHPC催化剂优异的ORR和OER双功能催化活性主要归因于高分散的Co3O4纳米粒子、三维连通的分级孔结构、高表面积以及具有协同催化作用的表面掺杂氮。最后,将Co3O4/NHPC催化剂制备空气电极,采用锌片为阳极组装锌-空气电池,进行了电池性能测试。结果表明,锌-空气电池开路电压达到1.39 V,峰值功率密度为80 mW cm-2,显著高于商业Pt/C作为空气电极材料组装的单电池(55.6 mW cm-2);在电流密度为20 mA cm-2时,电池比容量为674 mAh gZn-1(对应能量密度768 Wh kg-1Zn),比商业Pt/C组装的单电池高156 mAhgZn-1。该电池可在机械充电过程中稳定运行38 h。
[Abstract]:Zinc-air battery has the advantages of high specific energy, large capacity and low cost. It has a good application prospect in energy storage and electric vehicles. The core material of zinc-air battery is a bifunctional catalyst with the activity of oxygen reductive ORR and oxygen precipitate. At present, precious metals (such as PTR, IrO2 and so on) are mostly used, but the high cost and limited reserves hinder the commercialization of zinc-air battery. Therefore, it is of great significance to develop high efficient non-noble metal bifunctional catalysts. In this paper, the biomass bovine bone with microcosmic ordered multistage structure was carbonized, and in situ nitrogen-doped fractionated porous carbon (NHPCs) material was prepared. The Co3O4/NHPC bifunctional catalyst was prepared by using NHPC as the carrier to support the cobalt trioxide Co _ 3O _ 4 nanoparticles. The effects of preparation conditions and composition of Co3O4/NHPC catalysts on the electrocatalytic properties of ORR and OER were studied. Firstly, using bovine bone as precursor and KOH as activator, high surface area NHPCs with microporous mesoporous and macroporous connectivity were prepared by pre-carbonization and carbonation activation. It is found that when the mass ratio of KOH to precarbonation product is 0.4, the maximum specific surface area of the prepared NHPC is 2047m2g-1g ~ (-1), and the nitrogen doping amount is 3.85. On this basis, the ultrahigh specific surface area and nitrogen doping of Co3O4/NHPC composite catalyst 路NHPC were prepared by oil bath hydrothermal method supported on Co3O4 nanoparticles supported on NHPC carrier, which could promote the high dispersion of Co3O4 nanoparticles. When the oil bath temperature is 80 鈩，

本文编号：1928589