Sol–gel-derived spinel Co3O4 films and oxygen evolution: Part II. Optimization of preparation conditions and influence of the nature of the metal salt precursor

The spinel-type Co3O4 films have been prepared on a conductive support using a sol–gel route at 350°C and their physicochemical and electrochemical properties towards O2-evolution in alkaline solutions using TGA/DTG, IR, XRD, SEM, conductivity, CV, impedance and Tafel polarization techniques were investigated. The results showed that the nature of the precursor influenced the roughness factor as well as the electrocatalytic activity of the oxide films for O2-evolution greatly. The ratio of molar concentrations of precursors (i.e. x=[CoSO4]/[LiOH]) also strongly influenced the electrocatalytic properties of the catalyst. The electrocatalytic activity in 1 M KOH was observed to be maximum for the catalytic film obtained at 0.67⩽x⩽1.33. The Tafel slope and the reaction order found on the active catalytic films were 50–56 mV decade−1 and 1.1–1.5, respectively. The activation energy of the reaction was observed to be approximately constant (47.8±0.6 kJ mol−1) at low potentials (0.58 and 0.60 V) only. This electrode has shown a good performance up to the observed current density of 1.0 A cm−2 in 30 wt% KOH even at 70°C.