Influence of the NaOH Concentration on the Hydrogen Electrode Reaction Kinetics of Ni and NiCu Electrodes. Issue 6 (23rd March 2020)

• Record Type: Journal Article
• Authors: Kuznetsov, Aleksey N.; Oshchepkov, Alexandr G.; Cherstiouk, Olga V.; Simonov, Pavel A.; Nazmutdinov, Renat R.; Savinova, Elena R.; Bonnefont, Antoine
• Is Part Of: ChemElectroChem. Volume 7:Issue 6(2020)
• Page Start: 1438
• Page End: 1447
• Publication Date: 2020-03-23
• Subjects: hydrogen electrocatalysis -- Ni and NiCu catalysts -- pH effect -- electron transfer theory -- sodium hydroxide; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.202000319
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: Nickel is a promising electrocatalyst for hydrogen electrode reactions in alkaline media. Its electrocatalytic activity for hydrogen oxidation and evolution reactions can be enhanced when its surface is partially covered by Ni (hydr)oxides or by associating it with Cu. In this work, the influence of the NaOH concentration on the hydrogen electrode kinetics on various Ni electrodes is investigated. On metallic Ni, the electrocatalytic activity (measured as an exchange current density normalized to the surface area of Ni) is almost constant between pH 12 and 14, whereas it decreases by a factor of two on partially oxidized Ni and on the NiCu/C electrode. Analyzing the current potential curves with the help of microkinetic modeling reveals that the Had and OHad binding energies on Ni do not depend on pH, whereas the rate constants of the Volmer and Heyrovsky reactions decrease with pH. The pH effect on the electron transfer elementary act is briefly discussed in the framework of a quantum mechanical theory. Abstract : When the OH − concentration matters : The pH value affects the electron transfer rate constants of the Volmer and Heyrovsky steps of the hydrogen oxidation and evolution reactions, presumably because of the pH‐dependent structure of the interfacial water layer. An increase in pH results in an important decrease in the activity of Ni/NiO x and NiCu/C electrodes, whereas the effect is less pronounced for metallic Ni, which is characterized by much stronger adsorption of Had .