(Invited) In Situ Electrochemical TEM and XAS Studies in Oxygen Evolution Reaction

Abstract

The design of a highly efficient, cost-friendly and the green water oxidation catalyst is one of the most challenging research areas in the field of sustainable energy. Despite the presence of promising research findings of active catalysts in OER, their stability during long-term water oxidation reactions remains unexplored. The almost infinite number of possible compositions of mixed oxides makes the latter a great challenge towards the improvement of the stability and activity of such OER catalysts for future applications in water splitting devices and batteries.[1] Modern advances in the fabrication of micro electrochemical cells for operando microscopy have opened new horizons to perform the real-time investigation of electrochemical dynamic behaviors at the electrode-electrolyte interface.[2,3] In this study, an in situ electrochemical TEM approach was employed to directly visualize the early stages of OER and screening the morphological evolution of catalyst on the working electrode surface. The aforementioned method was applied on La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), La0.8Sr0.2MnO3 (LSM) and LiNi0.33Mn0.33Co0.33O2 (LNMC) mixed oxides, respectively. Furthermore, electron atomic pair distribution function (ePDF) was used in order to obtain the quantitative insight into the structural changes of the electrode surface under operational conditions. The electrochemical stability and structural changes behavior of the catalysts during OER was studied using in situ electrochemical X-ray absorption spectroscopy (XAS). Moreover, this structural changing process was reinvestigated by several ex situ methods such as X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), Raman spectroscopy, transmission electron microscopy, (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Finally, we propose a novel mechanistic insight, which demonstrates that the ongoing quest for true catalysts design in OER is a dynamic and rapidly developing research area.