Understanding the activity and stability of electrode materials targeted for clean energy applications through diagnostic impedance measurements

本研究项目侧重于电化学能源系统先进材料的基础研究。特别是金属/金属合金纳米颗粒，先进的碳材料以及金属纳米颗粒与这些碳的组合。这些材料是许多电化学能源技术的核心，包括燃料电池、电解槽和电化学/超级电容器。这些技术有潜力在能源领域得到更广泛的应用，前提是可以改进材料的性能与成本比，以及它们的耐用性。除了材料本身的改进外，还需要改进诊断工具，以方便地评估电极健康状态的多个指标。******本提案的重点是研究和增强新的电极材料和改进电化学阻抗谱（EIS）测量作为诊断工具。我们最近开发了一种基于is的诊断方法，可以清楚地阐明电极降解发生的模式。在降解过程中，EIS曲线会发生特定的变化，这是特定催化剂层降解过程的特征，包括碳载体和离聚体的降解。此外，我们修改了传输线EIS模型，使双层电容（Cdl）可以与源自Pt上Hupd的法拉第伪电容（CF）分离。此外，我们已经能够证明源自Hupd的CF的大小与Pt表面积成正比，从而产生电位相关常数，从而能够从EIS测量中精确测量多晶Pt电极的电化学活性表面积。******这一套基于ei的工具在研究电极的稳定性和典型Pt/C电极以外的表面过程方面具有巨大的潜力。因此，我们正在进行的研究将集中在新的电极材料上，利用EIS来阐明电极表面如何随着时间的推移而变化，并量化活性表面物种，包括金属和碳基，以及这如何影响活性。长期目标包括检查结构与相关性质之间的关系，如电导率、电化学活性表面积、催化活性、容量和性能。此外，我们将寻求扩展我们的EIS方法，以便它可以普遍应用于定量电化学可定位的氧化还原物质结合到电极表面

This research program focuses on fundamental studies of advanced materials targeted for electrochemical energy systems. Specifically metal/metal-alloy nanoparticles, advanced carbon materials as well as combinations of metals nanoparticles with these carbons. Such materials are at the heart of numerous electrochemical energy technologies, including fuel cells, electrolyzers and electrochemical/super capacitors. These technologies have the potential to be more widely deployed in the energy landscape provided that improvements can be made in the performance-to-cost ratio of the materials, and also in their durability. In addition to improvements in the materials themselves, improvements are needed in diagnostic tools that can readily assess multiple indicators of the electrode state-of-health.******This proposal is focused on the study and enhancement of new electrode materials and the refinement of electrochemical impedance spectroscopy (EIS) measurements as a go-to diagnostic tool. We have recently developed an EIS-based diagnostic methods that can clearly elucidate the mode of electrode degradation occurring. Specific changes in the EIS profiles occur upon degradation that are characteristic of specific catalyst layer degradation processes, including the degradation of the carbon support and the ionomer. Furthermore, we have modified the transmission line EIS model so that double-layer capacitance (Cdl) can be separated from faradaic pseudo-capacitance (CF) originating from Hupd on Pt. Moreover, we have been able to show that magnitude of CF originating from Hupd is proportional to the Pt surface area, yielding potential-dependent constants that enable accurate measurements of the electrochemically active surface area of a poly-crystalline Pt electrodes from EIS measurements.******Together this suite of EIS-based tools has enormous potential to study both the stability of an electrode and also surface processes in applications beyond typical Pt/C electrodes. Thus, our ongoing studies will focus on novel electrode materials, employing EIS to elucidate how the electrode surface is changing over time and also to quantify active surface species, both metallic and carbon-based, and how this impacts activity. Longer-term objectives include an examination of the relationships between structure and relevant properties such as conductivity, electrochemically active surface area, catalytic activity, capacity and performance. Furthermore, we will seek to extend our EIS methodology so that it can be applied universally in the quantification of electrochemically addressable redox species bound to an electrode surface.**