Structure-performance relationships of Ir-Ru electrodes for oxygen evolution during dynamic operation

本课题研究质子交换膜水电解槽动态运行过程中析氧反应用Ir-Ru电极的结构-性能关系。虽然电解槽是“能源转型”中有效储存可再生能源的关键因素，但析氧是阻碍该技术广泛应用的最具挑战性和最复杂的反应之一。由于可再生能源的间歇性特性需要动态运行，因此复杂性变得更大。为此，需要对动态析氧过程中催化剂的过程有一个基本的了解。目前最先进的催化剂是基于纯Ir的，而Ir- ru阳极表现出优异的性能，但稳定性较低，包括氧化态、表面/体积结构、形貌甚至溶解的变化。催化剂结构和电化学活性之间复杂的相互作用尚不清楚，但对于实现高性能、耐用和低成本的电解槽至关重要。本提案的主要目的是深入了解动态运行过程中Ir-Ru阳极的析氧结构-性能关系。特别关注催化剂组成和氧化态的变化及其对反应动力学的影响，以及催化剂的活性和耐久性。我们将阐明在满载、部分负荷和动态运行时结构和性能是如何变化的以及什么限制了可行的运行范围。为了实现这些目标，我们将开发一种方法，将表征催化剂状态和结构的原位/operando光谱和光谱方法与先进的电化学方法和动力学建模技术相结合，分析和预测给定催化剂状态的性能。这种跨学科的方法包括用于操作x射线光谱的新细胞，以揭示动态操作过程中的结构，以及用于预筛选Ir:Ru成分和深入机制分析的在线电感耦合等离子体质谱和电化学光谱设置。operando光谱和电化学表征的结果与动力学模型相结合，描述了反应动力学和催化剂结构的变化及其相互作用作为（动态）操作条件的函数。经过实验验证的动力学模型可以深入了解催化剂的过程，并有助于解释测量结果。从本质上讲，这种实验和理论的结合不仅可以更深入地了解电催化剂的结构-性能关系，例如析氧，而且还可以预测动态操作期间的性能和确定有利的操作制度。此外，对析氧过程中催化剂动力学的理解将为开发新型催化剂铺平道路。

This project deals with the structure-performance relationships of Ir-Ru electrodes for oxygen evolution reaction during dynamic operation of proton exchange membrane water electrolysers. Whereas electrolyzers are key enablers for efficient storage of renewables within the "Energiewende", oxygen evolution is one of the most challenging and complex reactions hindering wide-spread application of this technology. The complexity grows even larger as the intermittent nature of renewable energy requires dynamic operation. For this purpose a fundamental understanding of the processes at the catalyst during dynamic oxygen evolution is required. Whereas state-of-the-art catalysts are based on pure Ir, Ir-Ru anodes show superior performance but lower stability, including changes in oxidation state, surface/bulk structure, morphology and even dissolution. The complex interaction of catalyst structure and electrochemical activity is not understood yet, but of utmost importance for enabling high performance, durable and low cost electrolyzers. The main objective of this proposal is to gain insight into the structure-performance relationships of Ir-Ru anodes for oxygen evolution during dynamic operation. Special focus is on changes of the catalyst composition and oxidation state and their effect on reaction kinetics, and as such on catalyst activity and durability. We will elucidate, how the structure and performance changes upon full load, partial load and dynamic operation and what limits the feasible operating range. To achieve these objectives, we will develop a methodology which interlinks in situ/operando spectroscopic and spectrometric methods, which characterize catalyst state and structure, with advanced electrochemical methods and kinetic modeling techniques, which analyze and predict performance for given catalyst states. This interdisciplinary approach includes new cells for operando X-ray spectroscopy to unravel the structure during dynamic operation and on-line inductively coupled plasma mass spectrometry and electrochemical spectroscopy setups for prescreening Ir:Ru compositions and in-depth mechanistic analysis. Results from operando spectroscopy and electrochemical characterization are combined with kinetic models that describe changes in reaction kinetics and catalyst structure and their interaction as a function of (dynamic) operating conditions. Experimentally validated kinetic models give insight into the processes at the catalyst and aid in interpreting measurements. In essence, this combination of experimental and theoretical efforts allows not only for a deeper understanding of structure-performance relationships of electrocatalysts, here exemplarily for oxygen evolution, but also for prediction of performance during dynamic operation and identification of favorable operating regimes. Moreover, the gained understanding of catalyst dynamics during oxygen evolution will pave the way for new catalysts.