Preventing Graphene From Restacking Via Bioinspired Chemical Inserts: Toward A Superior 2d Micro-Supercapacitor Electrode

Graphene-based composites are promising materials for supercapacitors due to the high specific surface area and electrical conductivity of graphene. Reduction of graphene oxide (GO) is a practical approach to obtain a graphene-like material, but it suffers from restacking of the graphene sheets. Herein, a two-dimensional composite electrode based on electrochemically reduced GO (ERGO) and polydopamine (PDA) is reported, where PDA is used as a "bioinspired chemical insert" to tackle with the restacking issue of graphene layers. This green and facile electrochemical fabrication method starts from electroreduction of GO followed by electro-oxidation of dopamine (DA), present in the same electrolyte, by a simple switch between a cathodic and an anodic potential. The optimized ERGO-PDA composite electrode possesses combined features of excellent capacitive behavior, with a relaxation time (tau(0)) of 0.88 s, high gravimetric and volumetric capacitances (178 F.g(-1) and 297 F.cm(-3), respectively, at 10 mV.s(-1)), and finally an excellent cycling stability at 100-2000 mV.s(-1) at least for 30,000 cycles. The DA electropolymerization yield monitored by a quartz crystal microbalance and X-ray diffraction measurements demonstrate that PDA is formed between the graphene sheets which prevents the sheets from restacking and facilitates species diffusion inside the composite, leading to a volumetric energy density of 8.6 mWh.cm-3 for a power density of 7.8 W.cm(-3). Additionally, the electrochemical quartz crystal microbalance demonstrates a dominant cationic charge compensation and a very efficient interfacial transfer characteristic since a totally reversible mass response during charge/discharge was observed for the optimized ERGO-PDA electrode.