Metal–organic framework-derived nanoflower and nanoflake metal oxides as electrocatalysts for methanol oxidation†

Abstract

The energy crisis is the most urgent issue facing contemporary society and needs to be given top priority. As energy consumption rises, environmental pollution is becoming a serious issue. Direct methanol fuel cells (DMFCs) have emerged as the most promising energy source for a variety of applications such as electric vehicles and portable devices. Unfortunately, the kinetics of methanol oxidation is slow and needs an electrocatalyst to improve the reaction kinetics and the overall fuel cell efficiency. Herein, a straightforward hydrothermal procedure was utilized to prepare copper, nickel, and cobalt-based MOF composites by altering the elemental molar ratios. Cu-MOF (MOFP1), Cu/Ni-MOF (MOFP2), and Cu/Ni/Co-MOF (MOFP3) were prepared after carbonization and characterized using several key techniques such as FTIR, XRD, SEM, and EDX. The SEM analysis reveals that the morphology of MOFP1 is spherical aggregated particles, while that of MOFP2 or MOFP3 is in the form of nanoflakes and nanoflowers. Moreover, upon application of these composites as electrocatalysts for methanol electro-oxidation in an alkaline medium of 1 M NaOH using cyclic voltammetry (CV) and chronoamperometry (CA) tests, the electrochemical performance of MOFP2 in 1 M methanol exhibits the best performance for methanol oxidation with a current density reaching 38.77 mA cm⁻² at a scan rate of 60 mV s⁻¹. This can be attributed to the unique porous open flower structure and the synergistic effect between copper, nickel, and 2-aminoterephthalic acid which develop its catalytic activity.