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Issue 20, 2020

Anodic molecular hydrogen formation on Ru and Cu electrodes

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Abstract

Electrochemical hydrogen adsorption and desorption, and the state of adsorbed hydrogen (*H) on metal surfaces are of fundamental interest as well as practical importance for the hydrogen evolution reaction (HER) and electrochemical hydrogenation reactions including CO2 and CO electroreduction. Here, we report a previously undiscovered phenomenon whereby *H desorbs as H2 during an anodic potential sweep at potentials anodic of (more positive than) the equilibrium potential of U0(H2/H+), hence at potentials where hydrogen desorption would be expected as H+. Using electrochemistry – online mass spectrometry, we observe, quantify, and characterize the phenomenon on two different materials in two different environments – Ru(0001) in acid and polycrystalline Cu in alkaline. For both Ru and Cu, the anodic H2 formation seems to coincide with *OH adsorption, which would be consistent with a displacement mechanism. We propose that a high barrier for the Volmer step causes some of the displaced *H to desorb as H2 (Tafel step) rather than the thermodynamically more favorable desorption as H+ (Volmer step).

Graphical abstract: Anodic molecular hydrogen formation on Ru and Cu electrodes

Supplementary files

Article information


Submitted
17 Jun 2020
Accepted
13 Aug 2020
First published
14 Aug 2020

Catal. Sci. Technol., 2020,10, 6870-6878
Article type
Paper

Anodic molecular hydrogen formation on Ru and Cu electrodes

S. B. Scott, A. K. Engstfeld, Z. Jusys, D. Hochfilzer, N. Knøsgaard, D. B. Trimarco, P. C. K. Vesborg, R. J. Behm and I. Chorkendorff, Catal. Sci. Technol., 2020, 10, 6870 DOI: 10.1039/D0CY01213K

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