Controlled Dealloying of Alloy Nanoparticles toward Optimization of Electrocatalysis on Spongy Metallic Nanoframes
Controlled Dealloying of Alloy Nanoparticles toward Optimization of Electrocatalysis on Spongy Metallic Nanoframes
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DOI：
10.1021/acsami.6b07309
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发表时间：
2016-09-14
影响因子：
9.5
通讯作者：
Wang, Hui
中科院分区：
文献类型：
--
作者：
Li, Guangfang Grace;Villarreal, Esteban;Wang, Hui
由外部刺激引发的多金属纳米颗粒的结构转变的原子水平的理解是至关重要的，以增强我们的能力，精细定制的关键结构参数，从而精确地调整纳米颗粒的性能。在这里，我们表明，在还原性气氛中的热退火后，Au@Cu2O核壳纳米颗粒转变成Au-Cu合金纳米颗粒，其组成化学计量可调，这是由其母体核壳纳米颗粒前体的相对核和壳尺寸预先确定的。的. Au-Cu合金纳米颗粒表现出明显的去合金化行为，这取决于它们的Cu/Au化学计量比。对于Au-Cu合金纳米粒子与Cu原子分数以上的分离极限，纳米孔隙度演变渗流脱合金发生后，暴露的合金纳米粒子适当的化学蚀刻剂，导致形成颗粒海绵状纳米框架与固体/空隙双连续形态组成的分层互连的纳米配体。逾渗脱合金过程中的纳米孔隙度演变由两个相互交织的结构重排过程协同指导，即热力学驱动的韧带域粗化和柯肯达尔效应驱动的骨架膨胀，这两者都可以通过控制逾渗脱合金过程中的铜浸出率来操纵。脱合金纳米框架具有反应物分子可接近的大的开放表面积和韧带表面上的催化活性欠配位原子的高丰度，这是高性能电催化非常期望的两个独特的结构特征。以甲醇的室温电氧化为模型反应，进一步证明了通过控制Au Cu合金纳米颗粒的渗滤脱合金，可以系统地调节脱合金金属纳米颗粒的电化学活性表面积和比活性，以达到最佳的电催化活性.
Atomic-level understanding of the structural transformations of multimetallic nanoparticles triggered by external stimuli is of vital importance to the enhancement of our capabilities to fine-tailor the key structural parameters and thereby to precisely tune the properties of the nanoparticles. Here, we show that, upon thermal annealing in a reducing atmosphere, Au@Cu2O core shell nanoparticles transform into Au-Cu alloy nanoparticles with tunable compositional stoichiometries that are predetermined by the relative core and shell dimensions of their parental core shell nanoparticle precursors. The. Au-Cu alloy nanoparticles exhibit distinct dealloying behaviors that are dependent upon their Cu/Au stoichiometric ratios. For Au-Cu alloy nanoparticles with Cu atomic fractions above the parting limit, nanoporosity-evolving percolation dealloying occurs upon exposure of the alloy nanoparticles to appropriate chemical etchants, resulting in the formation of particulate spongy nanoframes with solid/void bicontinuous morphology composed of hierarchically interconnected nanoligaments. The nanoporosity evolution during percolation dealloying is synergistically guided by two intertwining structural rearrangement processes, ligament domain coarsening driven by thermodynamics and framework expansion driven by Kirkendall effects, both of which can be maneuvered by controlling the Cu leaching rates during the percolation dealloying. The dealloyed nanoframes possess large open surface areas accessible by the reactant molecules and high abundance of Catalytically active undercoordinated atoms on the ligament surfaces, two unique structural features highly desirable for high-performance electrocatalysis. Using the room temperature electro-oxidation of methanol as a model reaction, we further demonstrate that, through controlled percolation dealloying of Au Cu alloy nanoparticles, both the electrochemically active surface areas and the specific activity of the dealloyed metallic nanoframes can be systematically tuned to achieve the optimal electrocatalytic activities.