Li-O2电池碳基催化剂界面反应的原位研究

Carbon-based materials are considered to be the preferred candidates for catalysts and carriers in Li-O2 cells owing to their high conductivity, good O2 adsorption and diffusion stability and design-ability. So this kind of materials has a large potential market in catalysis. However, carbon-based catalysts are unstable in the charging/discharging process due to Li2O2 or LiO2 and their reaction mechanism is not clear. In this proposal, we proposed an anchor-linking method to design and synthesize a family of novel “metal catalyst-anchor-carbon” composite catalysts to improve their stability, dispersion, and catalytic performance. We will choose the nanosized iron, cobalt, and nickel as an anchor to link carbon with layered structure and surface, and metal nanocatalysts including transition metals, rare-earth metals, noble metals and their alloys. N-doped carbon and loaded metal catalysts may have a suppressive effect on carbon-based catalysts for improving high-efficient Li-O2 cells. The interface, interaction mechanism, and distribution between multiple components of carbon-based catalysts will be investigated by Shanghai Synchrotron Radiation Facility (SSRF) which offer the advanced soft X-ray scanning microscopy and extended X-ray absorption fine structure (EXAFS). Furthermore, their reaction process, stability and catalytic mechanism of carbon-based catalysts in different electrochemical processes were investigated by the combination of in situ real-time X-ray technology and in situ electrochemistry in Li-O2 cells.

碳基催化材料以其高导电性、良好的O2扩散性能和可设计性等优点，被认为是锂氧电池中首选的多相电催化剂或载体。然而Li2O2或LiO2对碳基催化剂稳定性带来挑战，且影响机理尚不明确。碳基催化剂不稳定性限制锂氧电池碳基催化剂发展。本课题提出了新的“锚钉”路线，结合非石墨烯超薄碳材料特征，设计和合成一系列M-“锚钉”-C复合催化剂。根据不同碳基材料的微观结构，拟利用铁、镍、钴等材料作为纳米“锚钉”，固定过渡金属、稀土金属、贵金属及其合金催化剂。通过氮掺杂和负载催化剂的协同作用，提高碳基催化剂的催化活性和稳定性能，进而提高其在锂氧电池中的催化性能。通过利用上海光源的软X射线显微技术和近边X射线精确吸收分析，研究碳基复合催化剂，多组分间的相互作用机理和催化剂的分布状态。并通过软X射线分析技术和电化学分析结合，原位实时探测碳基催化剂在不同电化学过程中的反应过程、稳定性和催化反应机理。

金属-空气（M-O2）电池具有高容量密度和高能量密度，被认为是下一代最有竞争力的候选储能器件。发展金属-空气电池的关键是要获得具有高效氧还原和氧析出反应的正极催化剂，同时明确电极界面的多相催化机理。本项目设计了多种合成路线，包括固相相转变、配体强弱匹配和原位锚钉负载等方法，合成了一些列高活性单金属碳基催化剂（Co/N掺杂碳纳米片、Co/N掺杂碳纳米管、红毛丹结构Co-CN微球、单原子Co-NC催化剂、Fe-NC纳米片）、多金属基碳基催化剂（CoFe-NC催化剂、CoCu-NC催化剂、N掺杂CoNiOx催化剂）、磷酸盐基催化剂、钙钛矿基催化剂和原位锚钉Ru催化剂。通过利用上海光源的硬X射线吸收和软X射线精确吸收近边分析，确定了Co、Zn、Fe、C、N、O在催化剂本体和界面的分布和存在状态，并结合XRD、XPS和物理吸附等其他分析手段验证了催化剂相关组分的存在形式。基于其新颖的界面特征、导电性能和氧吸附性能等方面的协同作用，其氧还原和氧析出催化性能均得到不同程度的提升，并成功应用于锂氧电池、锌空气电池和新双氧水电池，表现出了较好的容量性能和循环稳定性。并进一步通过原位分析和反应后刨析，初步证实了催化剂的氧吸附性、催化剂的孔结构和氧气浓度对电池性能提升均有一定程度的影响。项目的研究为高性能电催化剂的可设计性、规模化合成以及在金属空气电池中应用奠定了理论和技术基础，为开发和应用新一代金属空气电池提供了新的思路和支撑。