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[Display omitted] • Recent progress in high spatial and energy resolution characterization techniques of water molecules on metal surfaces under ultra-high vacuum condition. • In-situ spectroscopic characterization of interfacial water during electrochemical processes. • Various discoveries on how interfacial water participate in electrocatalytic reactions. Water is a fundamental substance in the natural world, playing a central role in various fields such as energy, catalysis and the environment. Broadly speaking, the diverse applications of water in different domains are all reliant on its interactions at surfaces. This mini-review aims to provide a comprehensive overview of advanced characterization techniques employed in the examination of interfacial water. Through the presentation of recent findings regarding water's behavior on various surfaces, we elucidate how these newly developed characterization methods enable precise determination of the physical and chemical properties of interfacial water. Additionally, we delve into how these discoveries enhance our comprehension of the physical and chemical processes involving water. Of particular interest is the intricate relationship between interfacial water and catalytic activity in electrocatalytic reactions. Furthermore, we offer insights into the challenges and prospects within this captivating field of study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@RuO x core–shell nanostructures are fabricated to amplify the Raman signals. • Electroreduction of RuO x is in-situ studied using the borrowing SERS strategy. • Direct evidences of OH intermediate are obtained during RuO x electroreduction. • A two-step molecular pathway is proposed for RuO 2 electroreduction. RuO 2 is one of the most promising catalysts for oxygen evolution reaction (OER), a key reaction in water electrolysis. However, the fundamental insights about the structural evolution of RuO 2 under different electrochemical environments remain unclear. Herein, the molecular reaction pathways of the electroreduction of RuO x in alkaline and neutral conditions are identified using in-situ electrochemical surface-enhanced Raman spectroscopy. Au@RuO 2 core–shell nanostructures are fabricated to amplify the Raman signals of species adsorbed on RuO x surfaces. Using such core–shell nanostructures, direct spectroscopic evidences of OH intermediate during the RuO 2 electroreduction process are obtained, which is further confirmed by D 2 O isotopic substitution experiments. A molecular pathway that RuO 2 is reduced to Ru through a two-step reduction process has been proposed. This work provides insightful information on the structural evolution of RuO x with electrochemical environments. [ABSTRACT FROM AUTHOR]

We report the direct characterization of coke information in the clearly resolved (0 1 0) and (1 0 0) planes of various anisotropic MFI zeolites using EELS techniques, in a model reaction of methanol to hydrocarbons. For the first time, we found that the main coke species varied between different planes and depended on the crystal structure. The coke species was graphite carbon and polyaromatic hydrocarbon over MFI nanosheets and MFI with b -axis length 60 nm, respectively. The diffusion of aromatics out of conventional MFI zeolites was found only through the straight channels, while small molecules randomly diffused through both channels, resulting in different coke deposition on the (0 1 0) plane and the (1 0 0) plane from different precursors. As all product molecules diffused only through the straight channels, the MFI nanosheet showed a distinct crystal-plane selective effect of coke deposition, in contrast to nearly uniform coke distribution throughout the entire external surface for conventional zeolites. This anisotropic diffusion behavior influenced the gaseous and liquid products significantly, providing deep insight into the MFI catalyst for the selective control of products via crystal structure. [ABSTRACT FROM AUTHOR]