Hong Wei, Li Christina W
Department of Chemistry , Purdue University , 560 Oval Dr. , West Lafayette , Indiana 47907 , United States.
ACS Appl Mater Interfaces. 2019 Aug 28;11(34):30977-30986. doi: 10.1021/acsami.9b10158. Epub 2019 Aug 13.
Understanding the microstructural evolution of bimetallic Pt nanoparticles under electrochemical polarization is critical to developing durable fuel cell catalysts. In this work, we develop a colloidal synthetic method to generate core-shell Au@Pt nanoparticles of varying surface Pt coverages to understand how as-synthesized bimetallic microstructure influences nanoparticle structural evolution during formic acid oxidation. By comparing the electrochemical and structural properties of our Au@Pt core-shells with bimetallic AuPt alloys at various stages in catalytic cycling, we determine that these two structures evolve in divergent ways. In core-shell nanoparticles, Au atoms from the core migrate outward onto the surface, generating transient "single-atom" Pt active sites with high formic acid oxidation activity. Metal migration continues until Pt is completely encapsulated by Au, and catalytic reactivity ceases. In contrast, AuPt alloys undergo surface dealloying and significant leaching of Pt out of the nanoparticle. Elucidating the dynamic restructuring processes responsible for high electrocatalytic reactivity in Pt bimetallic structures will enable better design and predictive synthesis of nanoparticle catalysts that are both active and stable.
了解双金属铂纳米颗粒在电化学极化作用下的微观结构演变对于开发耐用的燃料电池催化剂至关重要。在这项工作中，我们开发了一种胶体合成方法，以制备具有不同表面铂覆盖率的核壳型金@铂纳米颗粒，从而了解合成后的双金属微观结构如何影响甲酸氧化过程中纳米颗粒的结构演变。通过比较我们的金@铂核壳结构与双金属金铂合金在催化循环不同阶段的电化学和结构性质，我们确定这两种结构以不同的方式演变。在核壳纳米颗粒中，来自核的金原子向外迁移到表面，产生具有高甲酸氧化活性的瞬态“单原子”铂活性位点。金属迁移持续进行，直到铂被金完全包裹，催化反应性停止。相比之下，金铂合金会发生表面脱合金化，并且铂会从纳米颗粒中大量浸出。阐明导致铂双金属结构具有高电催化活性的动态重组过程，将有助于更好地设计和预测合成既具有活性又稳定的纳米颗粒催化剂。
