高效碳基双功能氧电极催化剂的设计及其应用基础研究

Lithium-air batteries are considered the next-generation power sources for many applications. The commercialization of this technology, however, is hindered by a variety of technical hurdles, especially the sluggish kinetics of the oxygen electrode reactions (oxygen evolution and reduction reactions, OER/ORR). Precious-metal based electrocatalysts possess high electrocatalytic activity for oxygen electrode reactions, but high cost and scarcity largely hinder largescale application. Therefore, exploring non-noble materials with highly efficient bifunctional electrocatalytic activity, high-speed oxygen transfer channels and excellent conductivity for OER and ORR is still a great challenge. In this regard, we propose an ingenious approach to achieve efficient bifunctional electrocatalysis by designing novel carbonyl catalysts with alternate active sites. In this project, the study will focus on: i) using alternately assembling of active sites respectively for OER and ORR to enhance bifunctional electrocatalytic activity of catalysts; ii) using in-situ modification of graphene to meet both high-speed oxygen transfer channels and excellent conductivity of catalysts. Moreover, the project will also study the formation and regulatory mechanism of the bifunctional active sites from theoretical level, as well as the composition/structure-performance relationships between the composition, distribution, surface & interface structures of the active sites and the bifunctional catalytic activity. And then research the formation and decomposition mechanism of the discharging products in alternated active sites. In addition, illustrate the synergetic effect of compositions, pore structure and electronic conductivity of the catalyst on improved battery performance. As a result, a new class of porous carbon-based bifunctional catalysts with high activity and stability for OER and ORR will be designed and synthesized based on the above studies. The results will provide a novel design strategy to fabricate high performance non-noble bifunctional oxygen electrode, which will be of great realistic significance for accelerating the commercialization process of lithium-air battery.

针对锂空气电池氧电极非贵金属催化剂难于兼具高效双功能催化活性、氧传递通道以及高导电性这一极富挑战性的难题，本项目提出设计合成新型活性位分立的高效碳基双功能氧电极催化剂。拟通过将催化氧还原反应的高性能活性位和催化析氧反应的高性能活性位,在纳米尺度上进行交替组装来实现催化剂高的双功能催化活性，并探索利用石墨烯骨架的原位修饰来实现对催化剂高效氧传递通道以及高导电性的兼顾。本项目将从理论层面上系统研究分立式活性位的形成及调控机制，以及活性位的组成、分布和表界面结构对双功能催化性能的影响规律；并揭示放电产物在分立活性位上的形成和分解机制，阐明催化剂的组成、孔道结构以及导电性对改善电池性能的协同机制，最终获得对氧还原和析氧反应兼具高催化活性和高稳定性的新型多孔碳基双功能催化剂。该研究将为高效非贵金属双功能氧电极催化剂的设计提供新的思路，对发展金属空气电池具有重要的现实意义。

项目研究团队依托本项目，在碳基氧电极催化剂的设计、制备，以及结构和性能调控方面开展了系统的研究工作。成功研制出了对氧还原和析氧反应兼具高催化活性和高稳定性的高效碳基双功能催化剂，并应用于锂空气电池实现了150圈以上的稳定循环；采用石墨烯和盐封装的限域热处理策略，成功制备出了系列可媲美商业化贵金属催化剂的多孔碳基氧电极催化剂，并获得了对催化剂催化活性、利用率以及稳定性同步优化提升的有效策略；创新性地提出了利用双缩脲反应原位构建碳包覆金属纳米粒子复合催化剂的新思路，基于该策略实现了对金属表面碳覆盖度的可控调控；本项目还借助理论计算和原位表征技术，从理论层面上阐明了催化剂的双功能催化作用机制。项目研究成果为高效碳基氧电极催化剂的设计和构建提供了理论和实验依据。此外，本项目还拓展研制了高选择性的氮还原催化剂，分别从高效类锂氮还原催化剂的设计、析氢竞争反应的平衡着手，探索了可同步提升氮还原产氨速率和电流效率的通用策略。在本项目的资助下，共计在Joule、Angew. Chem. Int. Ed.、Adv. Mater.等国际知名学术期刊上发表SCI论文14篇，申请中国发明专利6件。