This special issue covers recent topics in solid-liquid interface research. Focusing on recent measurement and analysis techniques, as well as information and computational methods, it provides a clear explanation of the progress and challenges in the study of solid-liquid interfaces.

Surface-selective terahertz spectroscopy can provide rich information about dynamic behaviors of ions and solvent molecules in the vicinity of electrode surface, which helps us to get deeper insights into electrochemical reactions at the molecular level. However, there existed technical limitations to conduct such spectroscopic studies in the terahertz region. Recently, we have developed a terahertz vibrational analysis method for surface-enhanced Raman spectroscopy, in which a measured spectrum is converted to a vibrational density of states format. This review introduces some examples of our terahertz spectroscopic studies performed at various electrochemical interfaces.

Although recent advances in modern computational methodologies, the rational design of electrocatalysts remains a formidable challenge. This difficulty arises primarily from two factors : (1) the intrinsic complexity of electrode processes associated with the reactions of interest, such as hydrogen evolution reaction or oxygen evolution reaction, and (2) the insufficient availability of detailed microscopic mechanistic insights of these electrode processes. In this essay, a simple data-driven approach is presented with the aim of reducing the time-consuming trial-and-error phases in the optimisation of electrocatalyst synthesis, thereby allowing greater time on elucidating the fundamental questions why the materials identified through data-driven approaches exhibit better electrochemical properties.

Electrochemical reactions are governed not only by electrode materials but also by the interfacial reaction field composed of electrolyte solutions. This article reviews our recent studies demonstrating that strong coupling enables the design of the physicochemical properties of water as a reaction field. Strong coupling provides a new framework for electrochemical reaction control by modifying dynamic hydration-mediated ion transport and electron transfer pathways.

This article summarizes the author's recent research on numerical simulation of electrochemical processes and devices. Two approaches are presented : finite element method (FEM) simulations and ordinary differential equation (ODE) models. FEM enables detailed analysis of battery lifetime and pH distribution in electrolysis, whereas ODE models, based on Randles-type circuits and Nernst diffusion layers, capture essential dynamics such as pH variations and corrosion oscillations. Together, these methods offer device-level analysis and mechanistic insight for next-generation electrochemical technologies.

Part 2 explained the fundamentals of chemical reaction kinetics for CVD and ALD. This lecture applies these principles to the analysis of CVD reactions. First, Arrhenius plots illustrating typical CVD systems are presented, revealing chemical reaction rate-limited and mass transport rate-limited regions. In the mass transport-limited region, supply limitation exhibits zero activation energy and is temperature-independent. Reaction order analysis indicates surface reaction limitation. At high partial pressure, surface reactions reach adsorption saturation, and the rate ceases to increase, consistent with the Langmuir adsorption–desorption model. These plots delineate kinetic regimes and inform process-window selection, which underpins the industrial optimization of CVD, including blanket tungsten-CVD (W-CVD). As an example, this approach is applied to fabricating Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) contact holes. Deposition under Langmuir-type high-pressure conditions achieves superior W filling and coverage. Finally, the surface reaction model and its corresponding rate equation are discussed.