Thanks to its unique properties such as: high conductivity, large specific surface area (2600 m²·g^-1) and high theoretical specific capacitance (550 F·g^-1) [1], graphene has attracted a lot of attention over last years as one of the most promising electrode materials for Electric Double Layer Capacitors (EDLCs).

Of all the reported routes to obtain a graphene-like material, the most favorable approach is the reduction of GO and in particular the electrochemical reduction of GO, which is considered to be an economical, simple, fast, and environmentally friendly method with a possibility of relatively large-scale production [2-3]. However, reduced graphene oxide (rGO) suffers from a small surface area due to the partial restacking of graphene sheets via π-π interactions [4]. Therefore, it is necessary to develop an effective and feasible route in order to avoid the re-stacking of rGO and to obtain graphene-based electrodes with high specific capacitance and good stability.

Here we present graphene-PDA composites as electrodes for micro-EDLCs fabricated by a facile electrochemical method [5]. In particular, we address the issue of rGO re-stacking by using PDA as a "chemical in-sert" between graphene sheets, but we also explore the impact of PDA on interfacial charge storage properties and cycling performance. The optimized ERGO-PDA electrode has the combined characteristics of excellent capacitive behavior with excellent cycling stability (Capacitance retention of 107% after 10000 cycles at 1000 mV/s). Furthermore, electrochemical analyses by quartz crystal microbalance demonstrate dominant cationic charge compensation and highly efficient interfacial transfer characteristics in the presence of PDA, a totally reversible mass response is observed (cathodic and anodic scans) (Figure 1), whereas a
hysteresis is noticed for pristine ERGO. The absence of hysteresis for the ERGO-PDA electrode indicates that the interfacial processes, electroadsorption/desorption of the active species, occur at a very similar rate. These findings demonstrate the favorable impact of PDA on rGO restacking issue and on the interfacial transfer characteristics.

1. Tan, Y. B.; Lee, J.-M., Graphene for supercapacitor applications. Journal of Materials Chemistry A 2013, 1 (47), 14814-14843.
2. Gao, W.; Debiemme-Chouvy, C.; Lahcini, M.; Perrot, H.; Sel, O., Tuning Charge Storage Properties of Supercapacitive Electrodes Evidenced by In Situ Gravimetric and Viscoelastic Explorations. Analytical Chemistry 2019, 91 (4), 2885-2893.
3. Guo, H.-L.; Wang, X.-F.; Qian, Q.-Y.; Wang, F.-B.; Xia, X.-H., A Green Approach to the Synthesis of Graphene Nanosheets. ACS Nano 2009, 3 (9), 2653-2659.
4. Banda, H.; Périé, S.; Daffos, B.; Taberna, P.-L.; Dubois, L.; Crosnier, O.; Simon, P.; Lee, D.; De Paëpe, G.; Duclairoir, F., Sparsely Pillared Graphene Materials for High-Performance Supercapacitors: Improving Ion Transport and Storage Capacity. ACS Nano 2019, 13 (2), 1443-1453.
5. Bouzina, A.; Perrot, H.; Sel, O.; Debiemme-Chouvy, C., Preventing Graphene from Restacking via Bioinspired Chemical Inserts: Toward a Superior 2D Micro-supercapacitor Electrode. ACS Applied Nano Materials 2021, 4 (5), 4964–4973.