酸性介质中非贵金属合金氮(硫)化物氧还原电催化剂的构建与性能

Efficient use of Pt resources and the development of low Pt or non-Pt fuel cell catalysts are people’s long-term goal. The development of low Pt or non-Pt electrocatalysts for oxygen reduction reaction (ORR) in acidic medium is even more critical. Usually people improve the ORR activity and stability by alloying Pt with cheap metals, meanwhile save with Pt. Recently, we have extended this alloying strategy to nitrides and sulfides. By alloying the cobalt nitride having high ORR activity in acidic medium (but poor stability) with the molybdenum nitride having high stability (but poor activity), the Co-Mo alloy nitride catalysts were obtained which present high activity and stability. Accordingly, based on the high ORR activity but low stability of Fe(Co) nitrides and sulfides, and high stability but low activity of Mo(W) nitrides and sulfides, this project plan to alloy these two compounds to construct Fe(Co)-Mo(W) dual and/or multi-alloy nitride and sulfide catalysts. Also we will systematically investigate the ORR performances of these new electrocatalysts in acidic medium, establish the qualitative and quantitative relationships between the performances and the compositions and structures, clarify the related mechanisms, and optimiz the new non-precious metal catalysts with excellent ORR performances in acdic medium, which is of great significance.

高效利用铂资源、发展低铂甚至非铂燃料电池催化剂是人们长期追求的目标，开发基于酸性介质的低铂或非铂氧还原电催化剂则更是关键。通常人们将铂与廉价金属合金化以提高催化剂的氧还原活性和稳定性，并节约用铂。最近，申请人将合金化策略拓展运用至氮化物及硫化物，通过将酸性介质中具有高氧还原活性的氮化钴（但稳定性差）与具有高稳定性的氮化钼（但活性差）两者合金化，获得了同时具有高活性和高稳定性的Co-Mo合金氮化物催化剂。据此思路，基于Fe(Co)氮化物、硫化物的氧还原活性高但稳定性低，而Mo(W)氮化物、硫化物的稳定性高但活性低的特点，本项目拟通过将这两类化合物合金化，构建Fe(Co)-Mo(W)双元或多元合金的氮化物和硫化物催化剂，系统深入地开展这类新型催化剂在酸性介质下氧还原性能与其成分、结构之间的定性和定量关系，认识作用机理，优化出性能优良的新型非贵金属氧还原电催化剂，意义重大。

本项目系统深入地研究了多类过渡金属合金化合物等非贵金属氧还原电催化剂，主要内容包括：先进电催化材料的构建，酸性介质中电催化性能与其成分、结构之间的定性和定量关系，作用机理及性能优化。主要进展包括：发展了先进电催化材料的构建新方法，获得了多个具有分级孔结构、大比表面积、高导电性的过渡金属化合物异质结构新材料，在氧还原等多种电化学反应以及电化学储能中均展现出优异性能，归因于其活性位点多、电荷/物料传输方便、导电性好的协同作用，成为开发高性能非贵金属氧还原电催化剂的源泉；对酸性介质中高活性的Fe/N/C以及近年来新出现的碳基无金属氧还原电催化剂进行了深入探索，得到了活性位点高度表面富集的Fe/N/C以及高活性的硫氮共掺杂非晶碳管氧还原电催化剂，丰富了酸性介质中具有优良性能的非贵金属氧还原电催化材料体系；针对文献报道的氮化铁、碳化铁氧还原电催化剂，通过系统深入的比较研究发现，只有在制备过程中引入固态氮源时（即只有当Fe源、N源、C源均存在时），所得催化剂才具有优良的氧还原活性，结合密度泛函计算，揭示了这类文献报道的氮化铁、碳化铁催化剂实际上就是Fe/N/C催化剂，澄清了文献中的模糊观点。本项目执行期间，在Acc. Chem. Res./Adv. Mater./Nat. Comm./Chem. Sci./ACS Catal./Sci. China Mater./Sci. Bull.等学术刊物发表24篇标注论文，被Nat. Catal.、Adv. Mater.、JACS等刊物广为引用。应邀在Adv. Mater.发表的综述“Carbon-based metal-free ORR electrocatalysts for fuel cells: past, present and future”成为该刊2019年最受欢迎的10篇论文(TOP10)之一，排名第6。在国内外重要学术会议作大会报告、主题报告及邀请报告20余次。