The Formation of Surface Oxides on Nickel in Oxalate-Containing Alkaline Media

Author(s)

van Drunen, Julia ^[1] ; Barbosa, Amaury F. B. ^[1] ; Tremiliosi-Filho, Germano ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: ELECTROCATALYSIS; v. 6, n. 5, p. 481-491, SEP 2015.
• Web of Science Citations: 5

Abstract

The electrochemical formation of alpha-Ni(OH)(2) and NiOOH in the presence of adsorbed oxalate in alkaline media is studied under well-controlled experimental conditions that include the variation of the system temperature (T = -10 to 20 degrees C), the scan rate (v= 20, 150, and 200 mV s(-1)), and the concentration of supporting electrolyte (0.10 and 0.50 M KOH). The studies are carried out using cyclic voltammetry (CV) with polycrystalline bulk nickel and nickel foams. In situ infrared spectroscopy with voltammetry confirms the adsorption of oxalate to the surface of nickel in the 0.10 to 0.30 V potential window, concurrent with the formation of the alpha-Ni(OH)(2) species. The presence of oxalate in the system increases the charge density (Q) for the formation of both the alpha-Ni(OH)(2) and NiOOH surface oxides. The Q values calculated under various conditions indicate that the presence of oxalate in the system encourages the formation of a full single monolayer (ML) of NiOOH in the first CV scan. Measurements carried out at room temperature demonstrate that an increase in v decreases the Q values for NiOOH in the presence of oxalate to minimum values achieved at nu >= 150 mV s(-1). An increase of KOH concentration results in the formation of a thicker layer of NiOOH both in the presence and absence of oxalate. The Q values of NiOOH reduction in conditions that favor the formation of one complete monolayer of NiOOH are used to calculate the specific surface areas of open-cell nickel foams. The calculation of electrochemical surface area using this method is discussed and evaluated with respect to calculations based on the charge of alpha-Ni(OH)(2) formation. (AU)

• FAPESP's process: 13/22277-4 - Development of electrochemical methods for the processing of lignocellulose biomass and the subsequent production of platform compounds and value added chemicals
• Grantee: Julia Jannie van Drunen
• Support Opportunities: Scholarships in Brazil - Post-Doctoral