超薄多金属纳米片材料的构筑及其增强氧还原催化性能研究

One of the biggest hurdles in impacting the development of fuel cells is the sluggish kinetic for oxygen reduction reaction (ORR) at cathode. Pt is the most effective metal for catalyzing ORR, however, its high cost and very limited supply of Pt in nature greatly restrict the industrialization of fuel cells. Engineering Pt-based nanocrystals with high Pt catalytic efficiency provides a new strategy for enhancing ORR with high activity and stability. Based on the particular chemical and physical properties of ultrathin multimetallic nanosheets with few atomic thickness, in this project, we will explore new high-temperature organic phase and hydrothermal routes for preparing a series of novel ultrathin multimetallic nanosheets. Through tuning their thickness, composition and structure, the electrocatalytic performance for ORR will be optimized. We will further develop the self-assembly technique for assembling ultrathin multimetallic nanosheets with the optimized ORR activity onto graphene or three-dimensional (3D) graphene-based aerogels for further improving the catalytic efficiency of Pt. Finally, the design of ultrastable multimetallic nanosheets/microporous carbon core/shell composite materials will be explored in order to achieve the big enhancement of catalytic activity and stability. The present ultrathin multimetallic nanosheet project will have a big significance in developing high-performance and low-cost ORR catalysts, and broaden their practical applications in electrocatalysis and electroanalysis.

影响燃料电池发展的一个最大瓶颈之一是阴极催化剂催化氧气还原反应动力学比较缓慢。铂是目前最有效金属用来催化氧还原，然而它高的成本和自然界稀缺严重限制了燃料电池产业化。工程化铂基纳米晶提升铂催化效率，提供一个新的策略增强催化氧还原的活性和稳定性。基于超薄二维多金属纳米片独特的化学和物理属性，本项目拟探索新的高温有机相和水热合成路线制备一系列新型的超薄铂基多金属纳米片催化剂，通过调控它们的厚度、成分和结构等参数优化超薄纳米片催化氧还原性能；选取性能优越的多金属纳米片负载于二维石墨烯和三维石墨烯气凝胶分别构建层层超结构和金属纳米片/三维石墨烯气凝胶杂化材料，进一步提升Pt催化效率；并设计超稳定多金属纳米片/微孔碳壳复合材料，实现催化活性和稳定性极大增强。本项目的实施将对开发高性能、低成本的氧气还原催化剂具有重要意义，也将有力地拓展超薄金属片在电催化和电分析的实际应用。

在质子交换膜燃料电池中，缓慢的氧还原反应往往需要铂催化剂来提高反应效率，但铂催化剂的高昂价格和稀缺性是实现质子交换膜燃料电池规模应用的主要障碍之一。根据Sabatier理论，当催化剂与吸附的反应物或中间体之间的相互作用既不强也既不弱，处于适中程度时，催化反应活性最高。纯Pt或Pd与氧中间体的相互作用虽然优于其他金属，但仍与最优值有较大距离。本项目获得了一系列Pt基/Pd基超薄纳米结构，包括Pt基/Pd基合金纳米片，核壳结构纳米片，金属间化合物纳米片，纳米片与碳复合物，Pt基超薄纳米线等，有效提高了贵金属原子利用率，同时结合应变效应、电子效应、量子尺寸效应、表界面工程等优化了催化剂与中间体的吸脱附能，从而显著提升电催化性能。其中，双轴应变化的PtPb/Pt核/壳二维纳米片在0.9 V (vs. RHE)电位下质量活性达到了4.3 A mgPt-1；PdMo双金属烯由于量子尺寸效应及应变效应等在0.95 V电位下质量活性达到0.645 A mgPd-1，分别高出商用铂碳和钯碳16.9和107.5倍。这些工作在国际上引起了积极反响，推动了燃料电池相关催化剂的理论和实验研究。