基于壳层隔绝保护的MxN@Pt核壳结构电催化剂的制备与性能

To develop core-shell structured electrocatalysts using non noble metal as cores and platinum as shells is the most efficient approach to reduce platinum loading. However, the poor fitness of metal crystal lattices of core and shell usually constrains the growth of shell on the outside of the core, resulting in a series of structural defeats and further leading to low catalytic activity. Recent studies show that introducing nitrogen into the lattice of non-noble metals can expand the lattice, which efficiently increases the lattice comparability of non-noble metals and platinum used for core and shell respectively. Unfortunately, to produce high dispersive metal nitrides is still a big challenge for its further development. In order to address this problem, this proposed project is going to produce high dispersive metal oxides as precursor, and then synthesize high dispersive metal nitrides via nitridation reaction under the protection of the shell. Subsequently, taking advantage of special confined effect of the shell or epitaxy of high lattice comparability，the Pt shell will be controllably grown on the metal nitride core to achieve high catalytic activity via adjusting reaction thermodynamics and kinetics. By means of studying the reaction mechanism and optimizing the synthesis procedure, it is expected that the compositions of cores and shells, crystallinity and N atom-doping could be efficiently controlled. The interaction between the core/shell and catalytic performance will be investigated to correlate the core-shell structure with catalytic performance, and further provide a new method and theory for developing ultra-low platinum catalysts with highly catalytic performance.

构筑非贵金属为核，铂为壳的结构是实现超低铂含量电催化剂的最佳途径，但二者之间大的晶格失配度会导致壳层外延生长受限，进而带来系列结构缺陷，降低其催化效果。近期研究表明，氮原子填充到非贵金属晶格后，引起晶格扩张，能有效增大核壳之间晶格的匹配度。但是，高分散过渡金属氮化物的制备和壳层贵金属生长的有效调控仍然制约着其进一步发展。针对这一瓶颈问题，本项目首先以高分散金属氧化物为前驱体，利用壳层的隔绝保护作用，通过氮化反应制备高分散金属氮化物纳米颗粒；然后再利用壳层的限域作用或高晶格匹配度的外延生长，调整其反应热力学和动力学，在其表面可控生长铂原子，得到目标催化剂。通过反应机理的研究，优化材料制造工艺，实现对核、壳层材料的成分、结晶度和掺杂的有效调控；进而研究这些核-壳结构的相互作用及催化性能，获得其结构与性能之间的内在联系，为在微观层次研制稳定和高效的超低铂催化剂提供新思路和理论依据。

本项目对“基于壳层隔绝保护的MxN@Pt核壳结构电催化剂的制备与性能”进行了系统和深入的理论和实验研究，主要体现了以下几个方面的研究成果。1，通过对过渡金属含氮材料的设计策略和制备科学研究，基于复合材料的特征，发展了多种含氮过渡金属复合材料的制备方法，合成了多种碳氮基过渡金属低铂/非铂电催化剂；2，基于材料设计，对前驱体纳米粒子的制备、碳基材料的前驱体优选、形貌控制做了系统研究，发现MxN作为氧还原电催化剂及其包裹或复制低含量贵金属体现了高催化活性、高稳定性，并且在此基础上对MxN和MxN@Pt的氧还原电催化作用本质和增强机制进行了研究；3，利用多种制备技术进行材料控制合成和氧还原电催化性能研究，在此基础上，发展了包括低温熔融盐法、固相扩散法等多种材料制备方法，满足实际应用的普适要求来制备各种电催化剂和催化剂载体材料；4，通过对比不同微观结构的MxN及MxN@Pt催化剂对电催化反应的影响，获得了不同过渡金属氮化物性能与电催化反应活性及稳定性的内在关系，在催化材料设计上主要集中在新型氮化物催化剂及作为催化剂载体和催化体系的功能导向设计、合成和表征，在实质上解决电催化材料的催化活性、稳定性、成本等共性关键问题。本项目按时完成了预定任务。发表SCI期刊收录论文十余篇；申请中国发明专利2项；培养硕士毕业生3名。