Giant Redox Entropy in the Intercalation vs Surface Chemistry of Nanocrystal Frameworks with Confined Pores
Giant Redox Entropy in the Intercalation vs Surface Chemistry of Nanocrystal Frameworks with Confined Pores
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有限孔纳米晶体框架插层与表面化学中的巨大氧化还原熵
DOI：
10.1021/jacs.2c12846
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发表时间：
2023
影响因子：
15
通讯作者：
Khaliq, Faiqa
中科院分区：
文献类型：
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作者：
Huang, Jiawei;Marshall, Checkers R.;Ojha, Kasinath;Shen, Meikun;Golledge, Stephen;Kadota, Kentaro;McKenzie, Jacob;Fabrizio, Kevin;Mitchell, James B.;Khaliq, Faiqa
氧化还原插层涉及主体材料内的离子-电子耦合运动，在储能、电催化、传感和光电子学中有广泛的应用。单分散的MOF纳米晶体，与它们的体相相比，表现出加速的质量传输动力学，其促进了纳米限制孔内的氧化还原嵌入。然而，纳米尺寸的MOF显着增加了它们的外部表面积与体积比，使得嵌入到MOF纳米晶体中的氧化还原化学难以理解，这是由于将MOF颗粒外部的氧化还原位点与内部的纳米限制孔区分开的挑战。本文报道了Fe（1，2，3-triazolate）2的插层氧化还原过程，该过程的位移约为0.001。1.2 V来自颗粒表面的氧化还原。这种独特的化学环境不会出现在理想化的MOF晶体结构中，但在MOF纳米颗粒中会被放大。石英晶体微量天平和飞行时间二次离子质谱结合电化学研究确定了一个独特的和高度可逆的Fe 2 +/Fe 3+氧化还原事件发生在MOF内部的存在。实验参数的系统操作（例如，膜厚度、电解质种类、溶剂和反应温度）表明，该特征是由纳米限制（4.54 μ m）的孔引起的，该孔控制电荷补偿阴离子的进入。由于需要在MOF颗粒外部完全去溶剂化和电解质重组，内部Fe 2+位点的阴离子偶联氧化涉及巨大的氧化还原熵变（即，164 J·K-1mol-1）。总之，这项研究建立了一个微观图片的离子嵌入氧化还原化学在nanoconfined环境中，并展示了合成的可能性，调整电极电位超过一伏，具有深远的影响，能量捕获和存储技术。
Redox intercalation involves coupled ion-electron motion within host materials, finding extensive application in energy storage, electrocatalysis, sensing, and optoelectronics. Monodisperse MOF nanocrystals, compared to their bulk phases, exhibit accelerated mass transport kinetics that promote redox intercalation inside nanoconfined pores. However, nanosizing MOFs significantly increases their external surface-to-volume ratios, making the intercalation redox chemistry into MOF nanocrystals difficult to understand due to the challenge of differentiating redox sites at the exterior of MOF particles from the internal nanoconfined pores. Here, we report that Fe(1,2,3-triazolate)2possesses an intercalation-based redox process shifted ca. 1.2 V from redox at the particle surface. Such distinct chemical environments do not appear in idealized MOF crystal structures but become magnified in MOF nanoparticles. Quartz crystal microbalance and time-of-flight secondary ion mass spectrometry combined with electrochemical studies identify the existence of a distinct and highly reversible Fe2+/Fe3+redox event occurring within the MOF interior. Systematic manipulation of experimental parameters (e.g., film thickness, electrolyte species, solvent, and reaction temperature) reveals that this feature arises from the nanoconfined (4.54 Å) pores gating the entry of charge-compensating anions. Due to the requirement for full desolvation and reorganization of electrolyte outside the MOF particle, the anion-coupled oxidation of internal Fe2+sites involves a giant redox entropy change (i.e., 164 J K–1mol–1). Taken together, this study establishes a microscopic picture of ion-intercalation redox chemistry in nanoconfined environments and demonstrates the synthetic possibility of tuning electrode potentials by over a volt, with profound implications for energy capture and storage technologies.