Simultaneous shaping and reduction of binder-free electrochemically reduced graphene oxide electrodes through cathodic electrophoretic deposition (EPD)

Abstract

It is well known that the exposed specific surface governs the electrochemical performance of capacitive materials. In this context, the predominant strategy involves using sustainable 2D nanoparticles with a high specific surface area, with graphene being the most explored. The electrochemical behaviour of the material always depends on its intrinsic properties, but the processing route is a critical aspect to consider when it comes to exploiting the full inherent capability of the material to obtain high-performance supercapacitor electrodes. The configuration and arrangement of the formed microstructure are crucial for maximizing the electrochemically active sites of the material. This work presents an innovative colloidal approach for the cathodic electrophoretic deposition (EPD) of graphene oxide (GO). By modifying the GO surface with a cationic polyelectrolyte (polyethylene imine, PEI), the electrophoretic movement and deposition on the cathode are promoted. During the deposition process, the π electronic network of the GO is partially restored and the electronic properties of the substrate/coating interface are enhanced by the adjustment of the electrokinetic and suspension parameters. Results indicate an increase of 20% in the electrochemically active surface area (ECSA) for the same quantity of deposited electroactive material. This is a consequence of the more compact and active microstructures created over the 3D metallic substrates, following the electrically driven colloidal approach. The electrochemical characterization of the electrodes developed herein was compared with that of other reported ErGO electrodes, displaying a competitive supercapacitor behaviour with a specific capacity ranging from 148 to 80 F g⁻¹ (1.5–4.0 A g⁻¹), retention of 62%, and a power density of 1.1 × 10³ W Kg⁻¹.