Ions play a fundamental role in solid-liquid interface processes, whether as essential or undesirable components, highlighting the need for precise and quantitative real-time monitoring. Electrochemical sensors are identified as promising tools, particularly for field-deployable applications. However, conventional electrochemical sensing is inherently restricted to redox-active species and is often single use, constraining its scope. This study presents electrochemical impedance spectroscopy as an alternative for ion detection, utilizing physico-chemical interactions at the electrode-electrolyte interface. We introduce a first-principles model that describes the interfacial impedance behavior and shows how ion specific processes shape the impedance response. Based on this framework, an extensive dataset is compiled, and a machine learning model is trained to predict electrolyte composition with consistent accuracy, demonstrating detection limits at the parts-per-billion level. The findings indicate that this method has considerable potential as a real-time method for ion sensing, providing a perspective on selectivity and sensitivity beyond traditional electrochemical approaches. This work could serve as a foundation for advanced models of impedance behavior, and development of impedance-based sensors with applicability in complex environments, including biological fluids and industrial liquids.

In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB and OreC) for HIsarna ironmaking were analysed as an isolated process with a symmetrical thermogravimetric analyser (TGA) under an inert atmosphere. Using various methods, the chemical and mineralogical composition, particle size distribution, morphology and phase distribution of the ores were analysed. The ores differ in their mineralogy and morphology, where OreA only contains hematite as iron-bearing phase and OreB and OreC include goethite and hematite. To obtain the kinetic parameters in non-isothermal conditions, the Coats–Redfern Integral Method was applied for heating rates of 1, 2 and 5 K/min and a maximum temperature of 1773 K. The TGA results indicate that goethite and hematite decomposition occur as a two-stage process in an inert atmosphere of Ar. The proposed reaction mechanism for the first stage of goethite decomposition is chemical reaction with an activation energy ranging from 46.55 to 60.38 kJ/mol for OreB and from 69.90 to 134.47 kJ/mol for OreC. The proposed reaction mechanism for the second stage of goethite decomposition is diffusion, showing an activation energy ranging between 24.43 and 44.76 kJ/mol for OreB and between 3.32 and 23.29 kJ/mol for OreC. In terms of hematite decomposition, only the first stage was analysed. The proposed reaction mechanism is chemical reaction control. OreA shows an activation energy of 545.47 to 670.50 kJ/mol, OreB one of 587.68 to 831.54 kJ/mol and OreC one of 424.31 to 592.32 kJ/mol.

The development of advanced catalysts with innovative nanoarchitectures is critical for addressing energy and environmental challenges such as the electrochemical CO2 reduction reaction (CO2RR). In this work, we present the synthesis of an innovative copper-sulfur planar structure, Cu-S-BDC, within a metal-organic framework (MOF) catalyst, which demonstrates 100% selectivity towards formate as the sole carbon product. Structural analysis and surface characterizations reveal that Cu-S-BDC exhibits quasi-two-dimensional inorganic building units, with Cu bonded to two S-CH3 groups and one BDC linker, while carboxylate groups adopt a bridging coordination mode. This unique arrangement not only imparts remarkable structural stability but also enhances the electronic properties of the MOF, as evidenced by a narrow band gap of 1.203 eV that facilitates efficient charge transfer and increased electrochemical current density in CO2RR. Notably, it offers a Faradaic efficiency (FE) of 92% for formate at an overpotential as low as -0.4 V vs. the reversible hydrogen electrode (RHE) in an aqueous electrolyte of 1 M KOH, as well as a current density of -25.8 mA/cm2 at -0.9 V vs. RHE, averaged over 24 hours of electrolysis. This study highlights a fresh perspective in the field of MOF electrocatalysts by demonstrating that engineering the metal coordination environment can significantly enhance the electronic properties and consequently improve the electrocatalytic performance of these materials.

Ions are fundamental to solid-liquid-phase processes, whether as essential components or contaminants, making precise and real-time monitoring necessary. Electrochemical sensors have been identified as promising tools, particularly for field-deployable applications. However, conventional electrochemical sensing is inherently restricted to species that participate in redox reactions and are often single use, limiting its scope. In this study, electrochemical impedance spectroscopy (EIS) is presented as a promising alternative for ion detection, utilizing physico-chemical interactions at the electrode/electrolyte interface. A first-principles model was developed to describe the impedance behavior of electrochemical interfaces, demonstrating how ion-specific interfacial processes influence electrochemical response. Based on this framework, an extensive EIS dataset was compiled, and an AI-assisted model was trained to predict electrolyte composition with high accuracy, achieving detection limits in the parts-per-billion (ppb) range. The findings indicate that EIS has significant potential as a complementary method for ion sensing, providing a novel perspective on selectivity and sensitivity beyond traditional electrochemical approaches. It is anticipated that this work will serve as a foundation for more advanced models of impedance behavior and EIS interpretation, as well as for the development of next-generation impedance-based sensors with broader applicability in complex environments, including biological fluids and industrial liquids.