The Nature of Hydrated Protons on Platinum Surfaces. Issue 69 (15th November 2017)

• Record Type: Journal Article
• Authors: Kim, Youngsoon; Noh, Chanwoo; Jung, YounJoon; Kang, Heon
• Is Part Of: Chemistry. Volume 23:Issue 69(2017)
• Page Start: 17566
• Page End: 17575
• Publication Date: 2017-11-15
• Subjects: hydrogen evolution reaction -- platinum -- protons -- surface analysis -- water–metal interface; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201703882
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The nature of hydrated protons formed at water/metal interfaces is one of the most intriguing research questions in the field of interfacial chemistry. We prepared coadsorption layers of hydrogen and water on a Pt(111) surface in ultrahigh vacuum and studied the ionization of adsorbed hydrogen atoms to H + ions by employing a combined experimental and theoretical approach. Spectroscopic evidence obtained by mass spectrometry and reflection absorption infrared spectroscopy as well as corresponding density functional theory calculations consistently show that adsorbed hydrogen atoms ionize into multiply hydrated proton species (H5 O2 +, H7 O3 +, and H9 O4 + ) on the surface, rather than H3 O + . Then, upon addition of a water overlayer, the metal‐bound hydrated protons spontaneously evolve into three‐dimensional fully hydrated proton structures through proton transfer along the water overlayer. The stability of hydrated protons on the Pt surface and their bulk dissolution behavior suggest the possibility that surface hydrated protons are a key intermediate in electrochemical interconversion between adsorbed H atoms and H + (aq) in water electrolysis and hydrogen evolution reactions. Abstract : Intermediates in Volmer reactions : Adsorbed hydrogen atoms ionize into multiply hydrated protons (H5 O2 +, H7 O3 +, and H9 O4 + ) on a Pt surface assisted by water layers. These hydrated protons spontaneously evolve into fully hydrated structures along the water overlayer. Surface hydrated protons may be important intermediates in the electrochemical Volmer reaction on a Pt electrode.