TY - JOUR
T1 - pH and Alkali Cation Effects on the Pt Cyclic Voltammogram Explained Using Density Functional Theory
AU - McCrum, Ian T.
AU - Janik, Michael J.
N1 - Funding Information:
The authors gratefully acknowledge support from the National Science Foundation DMREF Grant #1436206. I.T. McCrum acknowledges support from The Pennsylvania State University Diefenderfer Graduate Fellowship and NSF NRT #1449785.
Publisher Copyright:
© 2015 American Chemical Society.
PY - 2016/1/21
Y1 - 2016/1/21
N2 - Platinum electrode cyclic voltammograms show features at low potentials which correspond to adsorption/desorption processes on Pt(111), Pt(100), and Pt(110) facets that have traditionally been ascribed to hydrogen adsorption. The 100 and 110 associated features exhibit a dependence on pH beyond the expected Nernstian shift. Herein we use density functional theory (DFT) to explain these shifts. We examine the specific adsorption of hydrogen, hydroxide, water, and potassium onto the low index facets of platinum, Pt(111), Pt(100), and Pt(110). In support of a growing body of evidence, we show that the low potential features which correspond to adsorption/desorption on Pt(100) and Pt(110) contain contributions from the competitive or coadsorption of hydroxide. This allows us to simulate cyclic voltammograms for Pt(100) and Pt(110), as well as Pt(111), which match experimentally measured cyclic voltammograms in a pH = 0 electrolyte. Furthermore, we find that potassium cations can specifically adsorb to all three low index facets of platinum, weakening the binding of hydroxide. As potassium-specific adsorption becomes more favorable with increasing pH, this allows us to explain the measured pH dependence of these features and to simulate cyclic voltammograms for the three low index facets of platinum which match experiment in a pH = 14 electrolyte. This has significant implications in catalysis for hydrogen oxidation/evolution, as well as for any electrocatalytic reaction which involves adsorbed hydroxide.
AB - Platinum electrode cyclic voltammograms show features at low potentials which correspond to adsorption/desorption processes on Pt(111), Pt(100), and Pt(110) facets that have traditionally been ascribed to hydrogen adsorption. The 100 and 110 associated features exhibit a dependence on pH beyond the expected Nernstian shift. Herein we use density functional theory (DFT) to explain these shifts. We examine the specific adsorption of hydrogen, hydroxide, water, and potassium onto the low index facets of platinum, Pt(111), Pt(100), and Pt(110). In support of a growing body of evidence, we show that the low potential features which correspond to adsorption/desorption on Pt(100) and Pt(110) contain contributions from the competitive or coadsorption of hydroxide. This allows us to simulate cyclic voltammograms for Pt(100) and Pt(110), as well as Pt(111), which match experimentally measured cyclic voltammograms in a pH = 0 electrolyte. Furthermore, we find that potassium cations can specifically adsorb to all three low index facets of platinum, weakening the binding of hydroxide. As potassium-specific adsorption becomes more favorable with increasing pH, this allows us to explain the measured pH dependence of these features and to simulate cyclic voltammograms for the three low index facets of platinum which match experiment in a pH = 14 electrolyte. This has significant implications in catalysis for hydrogen oxidation/evolution, as well as for any electrocatalytic reaction which involves adsorbed hydroxide.
UR - http://www.scopus.com/inward/record.url?scp=84954519866&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84954519866&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.5b10979
DO - 10.1021/acs.jpcc.5b10979
M3 - Article
AN - SCOPUS:84954519866
VL - 120
SP - 457
EP - 471
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 1
ER -