Mastronardi Valentina, Magliocca Emanuele, Gullon José Solla, Brescia Rosaria, Pompa Pier Paolo, Miller Thomas S, Moglianetti Mauro
Nanobiointeractions & Nanodiagnostics, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
Department of Chemistry and Industrial Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova, Italy.
ACS Appl Mater Interfaces. 2022 Aug 17;14(32):36570-36581. doi: 10.1021/acsami.2c07738. Epub 2022 Aug 3.
Ultrasmall (<5 nm diameter) noble metal nanoparticles with a high fraction of {111} surface domains are of fundamental and practical interest as electrocatalysts, especially in fuel cells; the nanomaterial surface structure dictates its catalytic properties, including kinetics and stability. However, the synthesis of size-controlled, pure Pt-shaped nanocatalysts has remained a formidable chemical challenge. There is an urgent need for an industrially scalable method for their production. Here, a one-step approach is presented for the preparation of single-crystal pyramidal nanocatalysts with a high fraction of {111} surface domains and a diameter below 4 nm. This is achieved by harnessing the shape-directing effect of citrate molecules, together with the strict control of oxidative etching while avoiding polymers, surfactants, and organic solvents. These catalysts exhibit significantly enhanced durability while, providing equivalent current and power densities to highly optimized commercial Pt/C catalysts at the beginning of life (BOL). This is even the case when they are tested in full polymer electrolyte membrane fuel cells (PEMFCs), as opposed to rotating disk experiments that artificially enhance electrode kinetics and minimize degradation. This demonstrates that the {111} surface domains in pyramidal Pt nanoparticles (as opposed to spherical Pt nanoparticles) can improve aggregation/corrosion resistance in realistic fuel cell conditions, leading to a significant improvement in membrane electrode assembly (MEA) stability and lifetime.
具有高比例{111}表面畴的超小（直径<5nm）贵金属纳米颗粒作为电催化剂具有重要的基础研究价值和实际应用意义，尤其是在燃料电池中；纳米材料的表面结构决定了其催化性能，包括动力学和稳定性。然而，合成尺寸可控的纯铂形状的纳米催化剂仍然是一项艰巨的化学挑战。迫切需要一种工业规模可扩展的生产方法。在此，我们提出了一种一步法来制备具有高比例{111}表面畴且直径小于4nm的单晶金字塔形纳米催化剂。这是通过利用柠檬酸盐分子的形状导向作用，同时严格控制氧化蚀刻，避免使用聚合物、表面活性剂和有机溶剂来实现的。这些催化剂表现出显著增强的耐久性，同时在寿命初期（BOL）能提供与高度优化的商业Pt/C催化剂相当的电流和功率密度。即使在全聚合物电解质膜燃料电池（PEMFC）中进行测试时也是如此，这与人为增强电极动力学并最小化降解的旋转圆盘实验不同。这表明金字塔形铂纳米颗粒中的{111}表面畴（与球形铂纳米颗粒相比）在实际燃料电池条件下可以提高抗聚集/抗腐蚀性能，从而显著提高膜电极组件（MEA）的稳定性和寿命。
