Does a Thermoneutral Electrocatalyst Correspond to the Apex of a Volcano Plot for a Simple Two‐Electron Process?

• Published in: Angewandte Chemie International Edition 2020-06, Vol.59 (26), p.10236-10240
• Main Author: Exner, Kai S.
• Format: Article
• Language: English
• Subjects: Catalysts; Electrocatalysts; hydrogen evolution reaction; Intermediates; kinetics; microkinetic modeling; Reaction intermediates; thermodynamics; volcano plot
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202003688

Volcano analyses have been established as a standard tool in the field of electrocatalysis for assessing the performance of electrodes in a class of materials. The apex of the volcano curve, where the most active electrocatalysts are situated, is commonly defined by a hypothetical ideal material that binds its reaction intermediates thermoneutrally at zero overpotential, in accordance with Sabatier's principle. However, recent studies report a right shift of the apex in a volcano curve, in which the most active electrocatalysts bind their reaction intermediates endergonically rather than thermoneutrally at zero overpotential. Focusing on two‐electron process, this Viewpoint addresses the question of how the definition of an optimum catalyst needs to be modified with respect to the requirements of Sabatier's principle when kinetic effects and the applied overpotential are included in the analysis. Tip of the volcano: Electrode materials are classically assessed by their location on a volcano curve, using the binding strength of a reaction intermediate (RI) as a descriptor. For a two‐electron process, the apex of the volcano corresponds to thermoneutral binding of the reaction intermediate at zero overpotential. This Viewpoint addresses the definition of an optimum catalyst when kinetic effects and applied overpotential are factored in, illustrating a right shift of the volcano's top with increasing driving force.