Bipolar electrochemical deposition of HKUST‐1 on carbon and its loading with polypyrrole for supercapacitor electrodes

Wireless electrochemistry, an electro-synthesis of metal organic framework aided by a bipolar electrochemistry, creates an electrode-template with a good control over the pore size that is accessible for functionalization with an electro-active polypyrrole. The template morphology could be directly adjusted by modification of the reaction conditions, making the wireless templating a useful tool to create patterns in an easy electro-click reaction.

Abstract

Using bipolar electrochemistry, carbon paper (CP) is asymmetrically coated with copper metal. Subsequent anodic electrodissolution in a solution containing trimesic acid linkers results in HKUST-1 depositing on the carbon surface. The CP-MOF (metal organic framework) composite is then soaked in a pyrrole/isopropanol solution for several hours before undergoing oxygen/Cu-induced polymerization to fill the pores. Variations in the concentration and soaking time were investigated. X-ray diffraction shows the successful synthesis of HKUST-1 before and after pyrrole treatment. Scanning electron microscopy and optical microscopy suggest that the polymer is formed within HKUST-1 rather than as a coating. Further characterization by Fourier transform infrared, X-ray photoelectron spectroscopy, gas adsorption, and thermogravimetric analysis/differential thermal analysis were also carried out. Capacitance was found to increase with the concentration of pyrrole used to load HKUST-1. Higher concentrations also lead to more leaching of copper. Differential pulse voltammetry (DPV), galvanostatic charge discharge, and electrochemical impedance spectroscopy electrochemically studied the redox peaks, capacitance retention, and resistivity of the electrodes.

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