Preparation And Electrochemical Performance Of Porous Graphene Via Freeze Drying

In this paper, we reported a facile method to prepare Porous Graphene (PGR), Porour Graphene-Chitosan (PGR-CS) and Porous Graphene-MnO2 (PGR-MnO2) based on freeze-drying.The produced PGR and PGR composites materials exhibited three-dimensional interconnected porous structure.The results shows that the addition of surfactant introduced mesopores in the PGR and the oil droplets can improve the pore volume. Electrocatalytical activity towards glucose was also investigated, and the maximum electrocatalytical current reached 6.3 times for 5 mM glucose. The modified electrode was used to detect the glucose, and a low detection limit of 8.7 μM and a high sensitivity of 16.3μA mM cm-2 were obtained. The good sensing performance was attributed to the good three-dimensional porous structure and conductivity of the PGR.By adjusting the GR amount, the porous PGR-CS composites containing different GR content could be produced. It was found that the GR amount played an important role on their morphologies. Higher GR amount resulted in more pores appearing in the PGR-CS composites. When the GR amount was 70 wt%, the PGR-CS composites (PGR70-CS) had good flexibility and interpenetrating porous structures. Current response from the PGR70-CS composite modified glassy carbon electrode (PGR70-CS/GCE) was about two times that from the bare GCE with Fe(CN)63-/4- as a probe. The GOD modified GCE also showed good electrocatalytic activity for glucose. Using ferrocenecarboxylic acid as a mediator, a linear relationship from 0.14 to 7.0 mM between currents and the glucose concentration with a detection limit of 17.5 μM was obtained.Three dimensional (3D) PGR-MnO2 composites as electrode materials for supercapacitors were fabricated via deposition of MnO2 particles on 3D PGR produced from freeze-drying method. By immersing PGR into 0.1 M KMnO4/K2SO4 for different time, it was found that MnO2 particles with the size of about 200 nm were formed and uniformly distributed on the GR sheets. The obtained PGR-MnO2 composites still remained 3D interpenetrating porous structures. The results showed that the PGR-MnO2-2h composite (immersing the PGR into 0.1 M KMnO4/K2SO4 for 2 h) gave the best capacitive performance among these produced composites. The PGR-MnO2-2h composite gave the maximum specific capacitance of 800 F g-1 with the maximum energy density of 40 Wh kg-1 at the current density of 0.1 Ag-1.