颗粒多孔电极中操作电化学动力学的中尺度时空非均匀性定量研究
Operando Electrochemical Kinetics in Particulate Porous Electrodes by Quantifying the Mesoscale Spatiotemporal Heterogeneities
摘要：
电化学能量系统依赖于颗粒多孔电极来存储或转换能量。虽然三维多孔结构的引入，以最大限度地提高系统的整体性能的界面面积，时空异质性所产生的材料热力学本地化的电荷转移过程到有限的部分可用的接口。在这里，我们展示了一个简单但精确的方法，可以直接跟踪和分析的operando（即本地和反应）接口在介观尺度在一个实际的石墨多孔电极，以获得真正的局部电流密度，这原来是两个数量级高于全球平均电流密度通过现有的研究。我们的研究结果解决了长期存在的差异动力学参数来自电分析测量和第一原理预测。与普遍的看法相反，一旦多孔电极中出现时空反应不均匀性，电化学动力学就不受固态扩散过程控制。
英文摘要：
Electrochemical energy systems rely on particulate porous electrodes to store or convert energies. While the three-dimensional porous structures were introduced to maximize the interfacial area for better overall performance of the system, spatiotemporal heterogeneities arose from materials thermodynamics localize the charge transfer processes onto a limited portion of the available interfaces. Here, we demonstrate a simple but precision method that can directly track and analyze the operando (i.e. local and reacting) interfaces at the mesoscale in a practical graphite porous electrode to obtain the true local current density, which turned out to be two orders of magnitude higher than the globally averaged current density adopted by existing studies. Our results resolve the long-standing discrepancies between kinetics parameters derived from electroanalytical measurements and from first principles predictions. Contradictory to prevailing beliefs, the electrochemical dynamics is not controlled by the solid-state diffusion process once the spatiotemporal reaction heterogeneities emerge in porous electrodes.
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