The Impact of Operando Analysis in the Understanding of Oxygen Evolution Reaction Ranging from Intrinsic to Technical Scales

Abstract

The development of state of the art and cost-effective catalyst materials for the sluggish oxygen evolution reaction (OER) is of paramount importance for realizing practical water electrolysis for green hydrogen production. Crucial for this endeavor is the determination of the OER mechanism and a better understanding of all these background processes that affect catalyst activity and stability. Thus, to further elucidate all these processes operando characterization techniques performed dynamically during OER are used as powerful tools which allow monitoring of key reaction intermediates, active sites, charge transfer and material transformation coupled processes etc. In this work we summarize our recent investigations covering noble and 3d transition metal-based OER electrocatalysts by different operando techniques and we show the importance of such techniques in the unraveling catalyst activation/deactivation mechanisms. Thus, our efforts are ranging from half-cell characterization of electrocatalyst intrinsic properties to single-cell analysis of phenomena occurring during their technical operation.Operando techniques like eQCM, XAS, ICP-OES and single cell testing will be presented aiming to emphasize on the critical role of operando in the understanding of fundamental aspects of electrochemistry [1], like intrinsic catalyst properties (Fig. 1a), the effect of electrolyte impurities such as Fe (Fig. 1b-d) on Ni-based electrocatalysts in alkaline environment [2] as well as mechanistic phenomena taking place during catalyst activation (Fig. 1e-f) leading to the formation of the active sites for OER in acidic environment [3].