Operando X-ray diffraction (XRD) is an important characterization tool for real-time monitoring of structural changes in materials under different reaction conditions. In this study, we developed a laboratory-based diffractometer that could capture a full XRD spectrum within 10 s. The instrument has several advanced features. First, it uses a Ga–In alloy metal-jet X-ray source, thereby achieving high X-ray flux with a brightness of up to 3.0 × 10¹⁰ photons/(s·mm²·mrad²). Second, it employs an ellipsoidal mirror with a multilayer coating to produce quasi-parallel monochromatic light characterized by a divergence of 0.6 mrad and an energy resolution of 5.9 × 10⁻³. Third, it is equipped with a high-efficiency, high-signal-to-noise-ratio Pilatus 3R 1M detector for collecting diffraction signals. These features make the developed instrument applicable in studying rapid phase transitions in lithium-ion batteries, especially under extremely fast charge–discharge conditions. The data quality was comparable to that of synchrotron radiation XRD.

A comprehensive understanding of the dynamic processes at the catalyst/electrolyte interfaces is crucial for the development of advanced electrocatalysts for the oxygen evolution reaction (OER). However, the chemical processes related to surface corrosion and catalyst degradation have not been well understood so far. In this study, we employ LiCoO₂ as a model catalyst and observe distinct OER activities and surface stabilities in different alkaline solutions. Operando X-ray diffraction (XRD) and online mass spectroscopy (OMS) measurements prove the selective intercalation of alkali cations into the layered structure of LiCoO₂ during OER. It is proposed that the dynamic cation intercalations facilitate the chemical oxidation process between highly oxidative Co species and adsorbed water molecules, triggering the so-called electrochemical-chemical reaction mechanism (EC-mechanism). The results of this study emphasize the influence of cations on OER and provide insights into new strategies for achieving both high activity and stability in high-performance OER catalysts.

Understanding the dynamic structural and chemical evolutions at the catalyst–electrolyte interfaces is crucial for the development of active and stable electrocatalysts. In this work, β-Li₂IrO₃ is employed as a model catalyst for the oxygen evolution reaction (OER). Its elastic three-dimensional Ir-O framework enables us to investigate the Li⁺ cation dissolution-induced structure evolutions and the formation mechanism of amorphous IrO_x species. Electrochemical measurements by rotating ring disk electrode (RRDE) reveal that up to 60% of the measured OER current can be ascribed to catalyst degradation. A series of in-situ X-ray diffraction spectroscopy (XRD), X-ray absorption spectroscopy (XAS), and Raman spectroscopy are conducted. Structure vibration is observed with oxidation states of Ir being reduced abnormally during OER at high potentials. It’s hypothesized that the reversible proton intercalations are responsible for the Ir turn-over mechanism. Results of this work demonstrate a stable and elastic iridate structure and reveal the initial catalyst degradation behaviors during OER in acid media.