Zr-MOF@Polyaniline as an efficient platform for nickel deposition: Application to methanol electro-oxidation

Abstract

Polyaniline (PANI) was formed around a Zr-metal–organic framework (Zr-MOF) to improve its conductivity and electrochemical properties. Then, nickel nanoparticles was deposited by using a chemical reduction method to form Zr-MOF@PANI/Ni-NPs. The prepared nanocomposite was studied by different methods, such as, scanning and transmission electron microscopies (SEM and TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopies (EDX) and FT-IR. A core–shell structure was distinguished for Zr-MOF@PANI, which was decorated by Ni nanoparticles. The nanocomposite was drop cast on glassy carbon electrode (GCE). Highly improved electrochemistry of Ni was observed on Zr-MOF@PANI-Ni-NPs/GCE by cyclic voltammetry and electrochemical impedance spectroscopy. Then, electrocatalytic behavior of the modified electrode towards methanol oxidation reaction in alkaline solution (1.0 M NaOH) was studied. In comparison with stepwise-modified electodes, the oxidation current of methanol was highly increased on Zr-MOF@PANI-Ni-NPs/GCE, and exhibited stability after 200 potential cycles between 0.0 and +0.8 V (87% of the initial current maintained). Chronoamperometry showed the highest current density for Zr-MOF@PANI/Ni-NPs/GCE (110 mA cm−2) compared to stepwise modified electrodes. The excellent electrochemical performance toward oxidation of methanol (291.8 mAcm−2) was attributed to the good synergy between Zr-MOF, PANI, and Ni nanoparticles. The results of the present study shows that the nanocomposite may be considered as an alternative to Pt and Pt-based catalysts for alkaline direct methanol fuel cells (DMFCs).