Refined surface area determination of graphene oxide using methylene blue as a probe molecule: a comparative approach

Abstract

In this research, we explored the effectiveness of the methylene blue (MB) adsorption method as an alternative approach for determining the specific surface area of graphene oxide (GO). Initially, through a comparative analysis with reference activated carbon (AC), we identified the limitations of utilizing N2 physisorption for specific surface area determination of GO. Our findings revealed that the standard pretreatment process (heating under vacuum) before N2 physisorption led to damage to the surface oxygen groups on GO, and the measured surface areas (43 m2/g) do not accurately represent the entire surface area. To optimize MB coverage on GO, we conducted adsorption equilibrium experiments, focusing on controlling temperature and pH. The pH was significantly important in regulating the coverage of MB. Under the optimized MB adsorption conditions, the specific surface area of GO was 1555 m2/g. Our assumptions regarding specific surface area calculations were supported by structural characterization of samples with varying MB uptakes. The results confirmed a uniform coverage of MB on GO by SEM-EDX, XRD, and AFM.