Microwave irradiated nickel nanoparticles on Vulcan XC-72R carbon black for methanol oxidation reaction in KOH solution

• Ni nanoparticles were reduced on carbon support using microwave irradiation.
• The electron transfer rate constant of Ni/C-30 electrocatalyst is 7.54 × 10−2 s−1.
• OH− ions concentration controls the oxidation reaction with an order value of 1.15.
• Ni/C-30 showed the lowest impedance value, while the highest one was for Ni/C-10.

Ni/C electrocatalysts were prepared by chemical deposition of nickel nanoparticles on Vulcan XC-72R carbon black using microwave irradiation technique. The time of microwave irradiation during the reduction step and nickel weight percentage were varied. This was found to affect the morphology of formed Ni/C powder as shown by TEM analysis. Increasing nickel weight percentage results in the formation of more aggregated deposits. The electrocatalytic activity of different Ni/C samples towards methanol oxidation reaction in KOH solution was studied by applying cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopic techniques. Ni/C electrocatalyst containing 30 wt.% Ni [Ni/C-30] shows 5.2 times higher electrocatalytic activity than that with 10 wt.% Ni [Ni/C-10]. Heating Ni/C powder into microwave oven using the pulse mode of 30 s on/10 s off forms the most stable electrocatalyst for prolonged oxidation reaction. Electrochemical impedance measurements show that Ni/C-30 electrocatalyst has the lowest impedance value of 0.022 kΩ cm2, while the highest one is for Ni/C-10 [0.331 kΩ cm2] in (0.4 M methanol + 0.5 M KOH) solution at 500 mV. It confirms that Ni/C-30 has the highest electrocatalytic activity towards methanol oxidation reaction.

TEM image and Nyquist diagram of Ni/C-30 electrocatalyst in 0.5 M KOH solution in absence and in presence of 0.4 M methanol.Figure optionsDownload as PowerPoint slide