Sol-gel derived spinel MxCo3-xO4 (M = Ni, Cu; 0 <= x <= 1) films and oxygen evolution

Spinel-type binary transition metal oxides of cobalt and nickel (or copper) with composition MxCo3-xO4 (where M = Ni, Cu; 0 less than or equal to x le ss than or equal to 1) were synthesized in film forms by a sol-gel route an d their physicochemical and electrocatalytic properties have been investiga ted using SEM, XRD, cyclic and stationary voltammetries. The roughness fact ors, R-F, of electrodes made of these films were determined by AC-impedance and cyclic voltammetry (CV). The two procedures compared well, and enabled the discrimination between apparent and true (real) electroactivity toward s the oxygen evolution reaction (OER). Intermediate compositions showed a h igher activity despite a lower real surface area, and laboratory tests at 7 0 degrees C in 30 wt% KOH good practical performances. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.