Adsorption Dynamics and Electric Double Layer Properties at Pt(100) Electrodes

Abstract The electrode‐electrolyte interface governs many functional properties and processes, such as reaction rates, efficiency, and selectivity in electrochemical systems, with its structure and physicochemical phenomena being crucial for optimizing energy conversion and storage technologies. Platinum (Pt) is a state‐of‐the‐art catalyst for numerous electrocatalytic reactions. While Pt(111) is extensively studied, atomic‐level insights into interfacial properties of another basic surface, Pt(100), remain unresolved. Here, experimental techniques and first‐principles calculations are utilized to investigate adsorption behavior and adsorbate coverage at varying potentials as well as interfacial entropy in acidic media. The results reveal four voltammetric peak features: below peak I, hydrogen is the predominant adsorbate; between peak II and peak III, a mixed adsorption region with 22% hydroxide and 44% hydrogen forms, while at higher potentials, hydroxide coverage increases. The double‐layer structure is also explored, finding sensitivity of the double‐layer capacitance to electrode surface structure. For the first time, by combining in situ laser‐induced current transient and Raman spectroscopy, two potential values of maximum entropy are identified, indicating enhanced disorder and facilitated charge transfer, supported by disruption of the hydrogen‐bond network due to increased dangling bonds. These insights guide the rational design of efficient electrode‐electrolyte interfaces in Pt‐based nanostructured materials.