Effect of nickel oxide synthesis conditions on its physical properties and electrocatalytic oxidation of methanol

Nickel oxide (NiO) was synthesized using several methods and the various physical characteristics observed were correlated to differences in electrocatalytic activity, specifically relating to the oxidation of methanol in alkaline media. Room temperature NaOH-precipitated NiO showed the highest activity and stability towards methanol oxidation in hydroxide (0.005 M KOH) and carbonate (0.1 M Na2CO3) media of similar alkalinity. Rapid degradation of NiO electrodes was attributed to microcracking and disintegration associated with the formation of the γ-NiOOH/α-Ni(OH)2 redox couple, in addition to repeated scans through the oxygen evolution reaction region. Carbonate electrolytes also exhibited average current ranges 3–4 times higher and charge transfer resistances around 85% lower than hydroxide electrolytes. This suggests carbonate may provide a better medium in terms of higher activity and more moderate alkalinity for electrochemical reactions than hydroxide solutions.

► We synthesize NiO through several methods and correlate their electrochemical response with various physical characteristics observed by XPS, SEM and XRD.
► Room temperature, NaOH-precipitated NiO showed the highest activity and stability towards methanol oxidation in hydroxide (0.005 M KOH) and carbonate (0.1 M Na2CO3) media of similar alkalinity.
► Rapid degradation of NiO electrodes was attributed to microcracking and disintegration associated with the formation of the γ-NiOOH/α-Ni(OH)2 redox couple in addition to the oxygen evolution reaction.
► Carbonate electrolytes also exhibited average current ranges 3–4 times higher and charge transfer resistances around 85% lower than hydroxide electrolytes.