The Reversible Hydrogen Electrode:  Potential-Dependent Activation Energies over Platinum from Quantum Theory

Abstract

Potential-dependent activation energies are calculated quantum mechanically, using a local reaction center model, for the hydrogen reduction−oxidation reaction over platinum by the Volmer−Heyrovsky mechanism, Pt−H + H+ + e-(U) ↔ Pt + H2 (i), modeled by Pt−H···H+(OH2)(OH2)2 + e-(U) ↔ Pt···H−H···OH2(OH2)2 (ii). A contribution from the electrolyte to the potential of the reaction centers in ii is included in the ab initio Hamiltonian. The reversible potential predicted for i based on model ii is 0.04 V, close to the standard hydrogen electrode value of 0 V, and the predicted activation energy at the predicted reversible potential is 0.076 eV, close to the literature value of 0.12 eV for the apparent activation energy. The theoretical results validate the possibility of the Volmer−Heyrovsky mechanism being followed on platinum.

Calculated Phase Diagrams for the Electrochemical Oxidation and Reduction of Water over Pt(111)

“…Recent work, however, indicates that such conventions are emerging. 1,2,[6][7][8] It has, for example, been shown that many of the conventions from heterogeneous catalysis and gas-phase reactions can be applied to electrochemistry. 2 This requires a reference to connect the gas-phase surface calculations to those under electrochemical control.…”

Scanning electrochemical microscopy determination of hydrogen flux at liquid|liquid interface with potentiometric probe

“…SECM amperometric detection of hydrogen produced by proton reduction was earlier reported [12][13][14][15][16]. Here, we propose a SECM-tip potentiometric sensor based on reversible hydrogen electrode [17,18] and its application for hydrogen sensing next to a liquid|liquid (1,2-dichloroetane|water) interface. This approach is more advantageous for this task than amperometric detection due to the lack of analyte consumption.…”

Electrode Dynamics from First Principles

“…On this basis Cai and Anderson computed activation barrier for given electrode potential using a minimum-sized cluster consisting of a metal atom and a few water molecules. 4) On the other hand, Ishiwaka and co-workers took a dynamical approach. 5) They prepared the interface using a charged metal cluster on which water molecules were rained down, and conducted a short-time molecular dynamics (MD) simulation to follow electrochemical reaction that occurred soon after.…”