碳包覆Co基过渡金属核壳结构电催化剂的酸性氧还原活性位研究及其设计构筑

Non-PGM catalysts (primarily Fe based materials) for oxygen reduction reaction (ORR) are easily corroded and have poor durability in acidic media. Besides, the free iron ions during corrosion can combine with the hydrogen peroxide intermediate during ORR and form the Fenton reagent, which is highly oxidative and accelerates the fading processes. To address this issue, this project plans to develop Fe-free CoM@C (core@shell) electrocatalysts composed with bimetallic Co-based transition metal cores encapsulated by carbon shells. This catalyst is promising to significantly enhance the durability due to the effective separation between perishable CoM cores and acidic media, and avoiding the introduction of Fe element. In order to strengthen the understanding of Fe-free catalysts and further improve the acidic ORR performance of CoM@C catalysts, this project plans to synthesize encapsulating carbon shells on the preferential facets of CoM cores through rapid heating/cooling protocols. By tuning the compositions and preferential facets of CoM cores, the growing and characterizations of carbon shells are hypothesized to be tuned. The influence rules will be focused. Besides, we plan to reveal the synergetic effects between CoM cores and carbon shells on the free energy of ORR intermediates, as well as the structure-property relationships between CoM@C catalysts and ORR durability, and design & synthesize Fe-free CoM@C catalysts with high performance. At the same time, we also plan to address the problem in a different view of reducing peroxide production, i.e., design and synthesize hybrid catalysts of CoM@C and secondary components those have strong ability to decompose hydrogen peroxide.

以Fe为主的非铂族氧还原（ORR）电催化剂在酸性介质中易腐蚀、稳定性差，腐蚀产生的Fe离子与ORR中间产物过氧化氢结合可形成强氧化性的Fenton试剂，加速性能衰减。为解决该问题，本项目拟发展非Fe的碳包覆二元Co基过渡金属核壳结构（CoM@C，核@壳）电催化剂，将易腐蚀的CoM核与酸性电解质隔离，同时避免Fe元素。为加强对非Fe催化剂的理解，提升CoM@C在酸性介质中的ORR性能，本项目拟利用快速升降温热处理方法实现在CoM核的优势晶面上制备碳壳，通过调控CoM核的组成、优势晶面，实现对碳壳理化性质的调控，并研究其中的影响规律；基于CoM核与碳壳的组成、结构对活性位表面ORR中间产物吸附自由能的协同调变机制，及CoM@C与稳定性的构效关系，实现高性能非Fe的CoM@C催化剂的设计制备。与此同时，从减少游离过氧化氢的角度解决问题，设计构筑能催化过氧化氢分解的第二组分与CoM@C的复合催化剂

燃料电池可将化学能高效地转化为电能，是极具应用前景的新型能源系统，是缓解能源短缺和环境问题的重要一环。其阴极氧还原反应（Oxygen reduction reaction，ORR）是重要的电催化过程。作为ORR的主要发生场所，电催化剂的活性和稳定性决定了电化学装置的性能。为了降低催化剂成本，本项目针对非贵金属ORR催化剂展开研究。本项目在Co基燃料电池氧还原电催化剂方面取得了一系列成果，系统研究了金属有机化合物骨架前驱体材料中各组分比例对催化剂形貌、结构及氧还原性能的影响规律，发展了双氮源方法制备了高活性高稳定的Co-N-C催化剂材料，阐明了催化剂活性中心的构效关系。此外还探索了Co基氧化物催化剂、Co基有机均相催化剂在氧还原反应中的作用，进一步提高了Fe-N-C催化剂的稳定性，推动了非贵金属氧还原催化剂的实用化进程。但需要指出的是，尽管非贵金属ORR催化剂得到了极大的发展，但其在膜电极中的稳定性依然不足，还需要在膜电极方面展开相应的研究工作。本项目已经发表了研究论文或综述论文14篇，另有若干篇在投。在项目执行期间，开展了大量的国内国际合作，培养本科生2名、硕士研究生3名、协助指导博士研究生5名，负责人获得了广东省自然基金杰出青年项目资助。