An Oxalate Method for Measuring the Surface Area of Nickel Electrodes

Abstract

This work establishes a new method to measure the electrochemically active surface area (A ECSA ) of nickel electrodes, in situ. The addition of 0.08 mol L −1 of an oxalate salt to an alkaline electrolyte solution shifts the half-wave potential of the Ni(II)/Ni(III) redox pair by about −80 mV. Further, these peaks are very narrow. The sharpest peak in this work has a full width at half maximum (FWHM) of just 11 mV. This unusual sharpness is attributed to the layered structure of nickel hydroxides and the adsorption of oxalate from the solution on the (001) surface. This is supported by attenuated total reflectance infrared (ATR-IR) peaks measured at 1265 cm −1 , 1655 cm −1 , and 1713 cm −1 , which correspond to mononuclear bidentate oxalate bonded to nickel. At sufficiently fast potential scan rates (≥150 mV s −1 ), the adsorbed oxalate limits growth of the surface hydroxide to a single layer. During the reverse scan, the surface NiOOH/Ni(OH) 2 reduction peak is well-separated from other electrochemical processes and may be used to accurately and precisely measure the A ECSA . The error of this method is estimated at < 10%.

Nickel hydroxides and related materials: a review of their structures, synthesis and properties

“…The method approximates that the peak corresponds to the formation of a monolayer consisting entirely of α-Ni(OH) 2 . Recently, this method has been refined by adding an oxalate salt to the electrolyte, which is proposed to limit the surface hydroxide to a single layer [205]. Moreover, to avoid the problem of the concurrent formation of NiO x , this new method instead measures the Ni(OH) 2 /NiOOH redox pair.…”

Pd/Ni Synergestic Activity for Hydrogen Oxidation Reaction in Alkaline Conditions

“…[24][25][26][27][28][29] Compared with Pt, Pd exhibits both adsorption and absorption of hydrogen which complicate the calculations of the ECSA from the H-UPD region. CO-stripping is also difficult to apply due to the unknown chemical and This procedure for the in-situ simultaneous area determination of the two metals can be considered as an estimation.…”

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

“…The NiOOH formation and reduction processes were studied in solid tetrabutylammonium hydroxide hydrate electrolyte in the 170 to 298 K range as a proof of concept. This study was published as a short communication and provided limited data; the NiOOH film thickness was calculated to be 14 nm at T=298 K [24] which corresponds to approximately 17 ML of oxide [25,26].…”

“…A recent study by Hall et al [26] describes a novel approach for controlling the growth of the NiOOH species using what they refer to as an oxalate method. This method involves the addition of oxalic acid to the alkaline electrolyte to produce an oxalate salt that adsorbs to the surface of the nickel electrode at a potential value inferior to that of the NiOOH formation process.…”

“…The NiOOH reduction peak is well separated from other electrochemical processes allowing the determination of A ecsa using this method to be performed accurately and precisely (the error was estimated to be <10 %). This new tool for determining the A ecsa of Ni electrodes is extremely valuable because, as of yet, there is not a precise method that is agreed upon by the majority of researchers on this topic [14,26]. Although there are a number of methods available to determine the electrochemical surface area of an electrode [27,28], many of these methods cannot be applied to non-noble metals such as nickel.…”