High Specific Surface Area Nickel Mixed Oxide Powders LaNiO3 (Perovskite) and NiCo2O4 (Spinel) via Sol-Gel Type Routes for Oxygen Electrocatalysis in Alkaline Media

Analysis of the NiCo2O4 spinel surface with Auger and X-ray photoelectron spectroscopy

“…The homogeneity and bulk stoichiometry of the two samples were determined with powder XRD using a Rigaku Geigerfl ex diffractometer equipped with a Cu Kα anode. Diffraction features were sharp and agree in position and relative intensity with previously published XRD data [15]. No phase separation was observed in the bulk and no NiO, CoO, Co 3 O 4 or any of their hydroxides were detected by XRD.…”

“…NiCo 2 O 4 was also synthesized by a sol-gel method [15]. Equal volumes of aqueous 0.50 M nickel nitrate and 1.00 M cobalt nitrate were mixed thoroughly and precipitated as carbonates.…”

“…We present here the surface analysis of NiCo 2 O 4 prepared by two different solid state synthetic methods, thermal decomposition of nickel and cobalt nitrates mixed in appropriate stoichiometric amounts [4] and a sol-gel route [15]. Several different sample treatment conditions were also employed.…”

Nature of oxygen at rocksalt and spinel oxide surfaces

“…The powder samples (Ni 2 Co 2 O 4 and MnCo 2 O 4 ) were by necessity synthesized under flowing, dry air at atmospheric pressures [13][14][15][16] and exposed briefly ͑ϳ15 min͒ to ambient air in transferring them to UHV. This is ample time and opportunity for substantial hydroxylation to occur and the O 1s XP spectrum can arguably be fit to three or more peaks ͑Fig.…”

Comparison of the Spinels Co 3 O 4 and NiCo 2 O 4 as Bifunctional Oxygen Catalysts in Alkaline Media

“…In contrast, the reverse scan for the NiCo2O4 coating shows two broader features extending down towards the negative potential limit, again attributable to more complex electron transfer kinetics. In fact, however, several papers report voltammetry for NiCo2O4 in similar conditions [15][16][17][18][19][20][21][22][23][24][25] and the scans to negative potentials show significant variation and this is likely to result from different preparations. It should be recognised, however, that the exact oxidation states of the metal ions in both the asprepared and oxidised forms cannot be determined by voltammetry.…”