三维多孔复合双功能电催化材料的制备及性能研究

发布时间：2019-03-30 23:16

【摘要】：随着对清洁能源需求的增加,人们开始致力于开发高效率、低成本、环境友好型的可替代能源转换与存储系统。在燃料电池、金属空气电池和电解水等多种可再生能源技术领域中,开发出能够同时促进氧析出反应(Oxygen Evolution Reaction,OER)和氧还原反应(Oxygen Reduction Reaction,ORR)的电催化剂是一个技术关键。ORR在燃料电池和金属空气电池的电极反应中至关重要,而OER在电解水的阳极反应中发挥着重要的作用。因此,制备高性能、低成本的具有催化ORR和OER双功能的电催化剂,是目前亟待解决的一个科学难题和技术难点。本研究中,通过简单的制备方法将氧化亚钴(CoO)纳米颗粒嵌入到氮、硫双掺杂的碳纳米纤维网络(以CoO@N/S-CNF表示)中,制备了一种新颖的三维块体双功能电催化剂,用于催化OER和ORR。碳纳米纤维网络来源于具有大量官能团的生物质材料,该材料不仅为纳米颗粒成核提供了大量活性位点,而且保留了交错互联的三维多孔网络结构。该CoO@N/S-CNF复合材料具有较大的比表面积和较高的石墨化程度,有利于传质和电化学反应的电荷转移。通过测试表明,CoO@N/S-CNF具有优异的ORR电催化活性,在碱性介质中,起始电位约为0.84 V vs.氢标电极(RHE),并且稳定性和抗甲醇能力均高于商品化Pt/C催化剂。此外,它在电位为1.55 V(vs RHE)时电流密度达到了10 mA cm-2,这表明了CoO@N/S-CNF复合材料还是一种有效的OER电催化剂。作为一种双功能电催化剂,CoO@N/S-CNF的氧电极活动参数值(ΔE)为0.828 V,低于Pt/C和大多数非贵金属催化剂,这说明CoO@N/S-CNF复合材料可作为一种性能优异的ORR和OER双功能催化剂。可以推断CoO纳米颗粒和碳纳米纤维、氮/硫共掺杂之间产生的双协同效应促使CoO@N/S-CNF具有令人满意的双功能催化特性。同时,探究了升温速率对材料合成的影响,改变升温速率后合成了Co9S8CT/Co@N/S-CN新材料。生成的Co9S8CT/Co@N/S-CNF具有新颖的微观形貌,在碳纳米纤维表面以Co9S8为活性位点生长出了莲藕状的空心碳管。通过探究材料的电化学性能,发现Co9S8CT/Co@N/S-CNF具有一定的ORR催化活性和良好的稳定性。
[Abstract]:With the increasing demand for clean energy, people began to develop efficient, low-cost, environment-friendly alternative energy conversion and storage systems. In the field of renewable energy technologies, such as fuel cell, metal air cell and electrolytic water, (Oxygen Reduction Reaction, has been developed to promote both oxygen evolution reaction (Oxygen Evolution Reaction,OER) and oxygen reduction reaction (Oxygen Reduction Reaction,). The electrocatalyst of ORR is a key technology. ORR is very important in electrode reaction of fuel cell and metal air cell, while OER plays an important role in anode reaction of electrolytic water. Therefore, the preparation of high-performance, low-cost electrocatalysts with dual catalytic functions of ORR and OER is an urgent scientific problem and technical difficulties to be solved. In this study, a novel three-dimensional bulk bifunctional electrocatalyst was prepared by embedding cobalt oxide (CoO) nanoparticles into a carbon nanofiber network (expressed as CoO@N/S-CNF) doped with nitrogen and sulfur by a simple preparation method. Used to catalyze OER and ORR. Carbon nanofiber network is derived from biomass materials with a large number of functional groups, which not only provides a large number of active sites for nucleation of nanoparticles, but also preserves the three-dimensional porous network structure of staggered interconnection. The CoO@N/S-CNF composites have large specific surface area and high graphitization degree, which is beneficial to mass transfer and charge transfer in electrochemical reaction. The results show that CoO@N/S-CNF has excellent electrocatalytic activity for ORR. In alkaline medium, the initial potential is about 0.84 V vs.. The hydrogen-labeled electrode (RHE), and its stability and methanol resistance were higher than commercial Pt/C catalysts. In addition, when the potential is 1.55 V (vs RHE), the current density is up to 10 mA cm-2, which indicates that the CoO@N/S-CNF composite is an effective OER electrocatalyst. As a bifunctional electrocatalyst, the oxygen electrode activity parameter (螖 E) of CoO@N/S-CNF is 0.828 V, which is lower than that of Pt/C and most non-precious metal catalysts. This indicates that the CoO@N/S-CNF composite can be used as a bifunctional catalyst for ORR and OER with excellent performance. It can be concluded that the double synergistic effect between CoO nanoparticles and carbon nanofibers, N / S co-doping makes CoO@N/S-CNF have satisfactory bifunctional catalytic properties. At the same time, the influence of heating rate on the synthesis of Co9S8CT/Co@N/S-CN was investigated, and the new material was synthesized after changing the heating rate. The resulting Co9S8CT/Co@N/S-CNF has a novel micro-morphology and a lotus-like hollow carbon tube has been grown on the surface of carbon nanofibers using Co9S8 as the active site. By investigating the electrochemical properties of the materials, it is found that Co9S8CT/Co@N/S-CNF has a certain ORR catalytic activity and good stability.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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