Synthesis, characterization and applications of 3D porous graphene hierarchical structure by direct carbonization of maleic acid

This work reports the synthesis of a novel 3D porous graphene (PG) from maleic acid (HO2CCH=CHCO2H) used as a carbon source through a simple one-step carbonization process. The sodium carbonate (Na2CO3) was used as the skeletal substrate for 3D PG preparation and we observed that the ideal mass ratio of maleic acid (MA) to Na2CO3 is 1:4, which gives the highest yield and net carbon content for 3D PG preparation. The Na2CO3 decomposition temperature is greater than 550 °C which causes the release of CO2 and hence ultimately it produced 3D porous graphene (PG). The prepared 3D PG was characterized by X-Ray Diffraction (XRD), Raman Spectra, Transmission Electron Microscope (HRTEM), Scanning Electron Microscope (SEM), X-Ray Photoelectron Spectroscopy (XPS), and Brunauer Emmett Teller (BET) Surface area. The synthesized 3D architectural frameworks of graphene offered well-defined pores with a large surface area amounting to 567.56 cm2g-1. However, with increasing temperature above 700 °C, there is a decrease in surface area which can be attributed to the heat shrinkage and sintering or collapse of smaller diameter pores. Also at higher temperatures, Na2CO3 decomposes quickly which impart less effect on the morphology of synthesized graphene. In addition, electrochemical and adsorptive properties were also studied and a comparison is made with 3D rGO synthesized separately. The unique porous structure of 3D PG showed an excellent adsorption capacity of 433.3 (mg g-1) towards emerging pharmaceutical compound Atenolol and it further increases up to 642.4 (mg g-1) towards organic dye Rhodamine B, which is much higher than the 3D reduced graphene oxide rGO obtained by the chemical reduction process. Similarly, the as-synthesized 3D PG depicted enhanced oxidation and reduction properties as compared to 3D rGO as is evident from sharp anodic and cathodic peaks for the 3D PG prepared at 700 °C.