ZIF-8 nanoparticles thin film at an oil–water interface as an electrocatalyst for the methanol oxidation reaction without the application of noble metals

Abstract

Herein, the first example of a zeolitic imidazolate framework-8 (ZIF-8) nanostructured film at an oil–water interface is reported. This facile formation was conducted at room temperature, and the obtained film exhibited an excellent current density (32.7 mA cm⁻²) in the methanol oxidation process of fuel cells as compared to a Pt film (30.6 mA cm⁻²), Pd/ZIF (9.0 mA cm⁻²), Au-mercaptoacetic acid-HKUST-1 (0.3 mA cm⁻²), Ni/ZIF-8 (0.744 mA cm⁻²) and Co-MOF-71/graphene oxide (17.5 mA cm⁻²), where MOF indicates a metal–organic framework. The electrocatalytic activity of the ZIF-8 thin film was investigated using cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy and linear sweep voltammetry. Our results show that the long-term poisoning rate (δ) of the ZIF-8 film with δ = 0.1% is comparable to that of expensive catalysts and even that of the Pt metal in PtRuIr/C in the crystalline form or amorphous form with δ = 0.1% or δ = 0.13%, respectively. The as-synthesized ZIF-8 film exhibited the significantly high power of 15.4 mW cm⁻² when compared with the membrane electrode assemblies/PtRu (6.8 mW cm⁻²) anode catalyst. Our result for the ZIF-8 film is comparable to the data reported for MOFs and also commercial Pt/C and Pt/C E-TEK; this suggests that the ZIF-8 film would be a good candidate as an electrocatalyst for the methanol oxidation reaction process.