Ni–P–SnO2/C composite: Synthesis, characterization and electrocatalytic activity for methanol oxidation in KOH solution

Abstract

Ni–P–SnO2/C composite was prepared by electroless reduction of nickel ions on SnO2/C powder. The weight percentage of SnO2 in the prepared composite was varied as 2.5–20. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis were employed to investigate the morphology, particle size and chemical composition of Ni–P–SnO2/C composite. Nickel islands with an average diameter of 0.33 μm were formed in the composite containing 10 wt.% SnO2 [Ni–P–SnO2/C-10]. The electrochemical performance of Ni–P–SnO2/C composite in KOH solution was studied using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Its electron transfer coefficient and electron transfer rate constant values were determined as a function of SnO2 weight percentage. The impedance value was found to gradually decrease with increasing SnO2 content getting its lowest value in Ni–P–SnO2/C-10 composite. The effect of altering the sweeping potential and KOH concentration on NiOOH film thickness in Ni–P–SnO2/C composite was investigated. An enhanced electrocatalytic activity of the prepared composite towards methanol oxidation in KOH solution was shown. In presence of methanol, the diameter of semi-circle was greatly reduced to record a much lowered Rct value of 0.25 Ω cm2.