Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 65: Solid-Liquid Interfaces: Reactions and Electrochemistry III
O 65.9: Talk
Wednesday, March 19, 2025, 17:00–17:15, H6
On the pH-dependence of the Hupd peak in cyclic voltammograms of Pt-group nanoparticles — •Hedda Oschinski1,2, Simeon Beinlich1,2, Karsten Reuter1,2, and Nicolas Hörmann1 — 1Fritz-Haber-Institut der MPG, Berlin — 2Technische Universität München, München
Understanding the electrochemical behavior of hydrogen adsorption at Pt-group metal surfaces, particularly in the context of non-well-defined nanoparticle surfaces, is crucial for advancing electrocatalytic applications such as the hydrogen evolution reaction (HER). To this end, we provide insights into the non-Nernstian pH shifts observed for underpotential deposited Hupd-like cyclic voltammetry (CV) peaks on Pt, Ir, Pd, and Rh nanoparticles. Utilizing density-functional theory, we explore the potential-dependent stability of H and OH adsorbates at undercoordinated surface sites, emphasizing the role of non-ideal electrosorption valencies in these shifts. This identifies direct H-OH replacement as predominant mechanism behind the CV peaks and reveals a primary influence of partial charge transfer. The theoretical predictions show good agreement with experimental observations across various Pt-group metals, even over various surface coordinations, and provide insights into cation-specific effects at Pt across the entire pH scale. This work not only clarifies the origin of the Hupd-like peak shift within the water stability region, but also suggests the interfacial capacitance as a main descriptor for cation effects in the HER, paving the way for more detailed analyses of cation type, concentration, and interfacial solvent structure.
Keywords: Cyclic Voltammetry; Platinum; Partial Charge; Capacitance; Cation Effects