基于低共熔盐模板的高密度活性位Fe-N-C催化剂分子设计和可控制备

Developing catalysts with high performance and low cost for oxygen reduction reaction (ORR) has been one of the major challenges for large-scale application of fuel cells. Transition metal and nitrogen co-doped carbon (Fe-N-C) catalyst is one of the most promising alternative non-noble metal catalysts of Pt catalysts. However, its catalytic activity is still at a low level compared to Pt catalysts due to the insufficient active sites. In this application, we report a “salt-templating assistant carbonization” technique using a three-dimensional porous eutectic salt as a template for fabricating Fe-N-C catalyst for the ORR. The 3D porous eutectic salt possess low melt points and its molten state at elevated temperature can be used as a confined space to suppress the elimination and agglomeration of precursor and promote the final yield and nitrogen-doped efficiency of Fe-N-C during carbonization. Moreover, the 3D eutectic salt can act as a porogen to modulate the pore structure of Fe-N-C. The low melt point ZnCl2 will boil off and generate micro-/meso-pores during carbonization at elevated temperature. On the other hand, the removal of the residual high melt point KCl/NaCl through etching with HCl generates the mesopores and macropores. The “salt-templating assistant carbonization” approach utilized here is a facile and low cost way to prepare 3D porous Fe-N-C catalyst directly in large scales.

发展低成本、高性能的氧还原催化剂是实现燃料电池商业化的关键。针对现有Fe-N-C非铂催化剂存在的本征活性差、活性位密度低等一系列问题。本申请提出“高密度活性位Fe-N-C催化剂分子设计和可控制备”方案，以具有三维多孔结构的低共熔盐为模板剂和造孔剂，通过自组装、原位聚合等方法构建具有特定原子组成的金属有机聚合物，利用低共熔盐较低的熔融温度和熔融状态，控制聚合物高温碳化时的结构形貌转换，避免聚合物在高温碳化过程中的结构坍塌、烧结及热解损失，利用低共熔盐的模板和造孔作用，调控Fe-N-C催化剂的比表面积和孔结构，实现活性位密度和传质效率全面提升。

发展低成本、高性能的氧还原催化剂是实现燃料电池商业化的关键。针对现有Fe-N-C催化剂存在的本征活性差、活性位密度低等一系列问题。本申请提出“高密度活性位Fe-N-C催化剂分子设计和可控制备”方案，在项目执行过程中发表论文16篇，申请发明专利1项。取得的创新性成果有：（1）开发了基于低共熔盐的“半封闭”碳基催化剂辅助合成技术，解决了“全封闭”体系中易形成大量盲孔及“全开放”体系中存在的前驱体快速烧失、掺杂效率低及结构坍塌等问题，催化剂产率和氮含量大幅提升；（2）开发了具有世界最高单原子密度的Zn-N-C催化剂，绕开了传统Fe-N-C类催化剂由于溶出的Fe2+会与副产物H2O2反应生成氧化性极强的羟基自由基（Fenton效应）而加速腐蚀碳、质子交换膜和离子交联聚合物的难题；（3）以原子级分散Zn、Fe、N共掺杂碳材料（ZnFeNC）为载体，利用ZnN4和FeN4位点对H2PtCl6前驱体的强锚定作用，成功制备了Pt原子100%暴露在载体表面的多原子Pt催化剂（MAC-Pt/ZnFe-N-C）。