单原子分散Pt基ORR催化剂微环境要素的协同作用

In order to meet the urgent demand on the practical application of PEMFCs, the cathode using ORR catalyst with ultra-low Pt loading and good cycling stability should be developed immediately. In this project, a single-atom dispersion strategy will be proposed to improve the utilization rate of Pt. The microenvironmental factors influencing the Pt loading monoatomic dispersed system will be investigated, which will reveal the interaction nature and synergistic effect mechanism. And an ultra-low Pt loading monoatomic dispersed catalyst system will be developed in this project.With the help of defect engineering technology, the limitation of poor stability of two-dimensional materials and weak electron transfer ability of transition metal oxides will be overcame by the composite modification ffunctionalized graphene and transition metal oxides. The stable transition metal oxide-coated graphene formed will provide a supporting microenvironment for Pt monatomic dispersion. The Pt single atom will be anchored at defect site by the charge effect of transition metal oxide material defect site and Pt atom. Using the in-situ, ex-situ structural characterization techniques in chemical bond scale, the complex associations of activity and stability of single atom ORR catalyst between the defect type, defect density of the support, and the density, dispersibility, agglomeration state of anchored Pt single atom will be clarified. The Pt single atom will be anchored at defect site by the charge effect of transition metal oxide material defect site and Pt atom. Using the in-situ, ex-situ structural characterization techniques in chemical bond scale, the complex associations of activity and stability of single atom ORR catalyst between the defect type, defect density of the support, and the density, dispersibility, agglomeration state of anchored Pt single atom will be clarified. Taking this as boundary condition, the density functional theory and monte carlo molecular simulation will be performed. Finally, an ideal Pt single atom catalyst model will be built, which will set a scientific foundation for the design of high efficiency ORR catalysts with ultra-low Pt loading.

针对燃料电池实用化对阴极氧还原（ORR）催化剂的超低Pt及长寿命的迫切需求，本项目提出大幅度提升Pt利用率的单原子分散的解决策略，深入研究影响Pt单原子分散的各微环境要素之间的相互作用本质和协同效应机理，并创制超低Pt载量的单原子分散的催化剂体系。借助缺陷工程手段，选择功能化石墨烯与金属氧化物进行复合改性，突破二维材料稳定性差与金属氧化物电子传递能力弱的限制，形成稳定的金属氧化物包覆石墨烯为Pt单原子分散的承载微环境，利用金属氧化物材料缺陷位点与Pt原子之间的电荷作用机制将Pt单原子锚定在缺陷位；结合原位、非原位等化学键级别的结构表征技术，厘清载体的缺陷类型、缺陷密度等因素与所锚定的Pt单原子密度、分散性、团聚态对ORR活性与稳定性之间的复杂关联；并以此为边界条件，开展密度泛函计算和蒙特卡罗分子模拟研究，建立理想Pt单原子催化剂模型，为新型超低载量高效Pt基催化剂的设计与制备提供科学依据。

协同效应助力团簇型催化剂实现超低铂PEMFC高效表达。降低 Pt 负载不仅会降低整体 ORR 动力学，还会在高电流密度区域 (HCD) 中导致严重的传质问题。本研究中我们通过热力学自发自组装获得超细且均匀的 Pt 簇 (1.3 ± 0.4 nm)，负载在 N、P 掺杂碳纳米片催化剂上，超细 Pt 簇通过强金属-载体相互作用稳定并且实现了超高分散度，服役状态下Pt的原子利用率和电化学活性面积得到提升。组装的膜电极在H2/Air燃料电池中的高电流密度区表现出了低的电压损失和高的峰值功率密度，表明该超低铂燃料电池阴极在高电流密度区的有效传质空间被充分利用，证明了其在解决局域传质问题方面的显著优势。