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

Abstract

The electrochemical formation of α-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°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 α-Ni(OH) 2 species. The presence of oxalate in the system increases the charge density (Q) for the formation of both the α-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 v ≥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 α-Ni(OH) 2 formation.

Regular Dimpled Nickel Surfaces for Improved Efficiency of the Oxygen Evolution Reaction

“…At −0.4 V versus Hg/ HgO the surfaces contain a Ni phase composed of β-Ni(OH) 2 . 32,33 The first peak in the forward scan, which was located at 0.45 V, is attributed to the reversible oxidation of β-Ni(OH) 2 to β-NiOOH. The cathodic peak at 0.28 V in the reverse scan is the reduction of β-NiOOH and formation of the β-Ni(OH) 2 phase.…”

Recent Advances in the Understanding of Nickel-Based Catalysts for the Oxidation of Hydrogen-Containing Fuels in Alkaline Media

“…This approach was later adopted to measure the ECSA of a Ni foam. 112 In this case sharp and narrow peaks for the Ni(OH)2/NiOOH oxidation-reduction processes were observed in the CVs, resulting in higher precision of the determined ECSA value of Ni assuming a specific charge of 195 µC cm -2 . However, the latter method can only be applied either after measuring the catalytic activity of an electrode, or in a separate experiment, since the presence of the oxalate salt in the electrolyte will most likely affect the electrocatalytic properties of Ni.…”

Modified Nickel Nanowires for Electro-Catalytic Oxidation of Formaldehyde in Alkaline Solutions

“…Amperometric measurements confirmed two broad linearity ranges (from 0.01-2 mM and 2-20 mM) and fast response (3s). Taking into account the determined electrochemically active surface areas (Aecsa) (determined by oxalate method [6,14]) we have been able to calculate the sensitivities: 0.3419 mA L cm −2 mmol −1 and 0.0458 mA L cm −2 mmol −1 . The receptor element has a detection capabitility of 0.8 μmol L −1 (experimentally determined and calculated according to the IUPAC recommendation).…”