GH/GOs/rGO reinforced alkaline and acid-activated geopolymers: a comparative study of microstructural and optical properties

There is an increasing demand for new materials that deliver comparable properties to traditional ones while requiring less energy to cure. The aim of the current research work is to investigate the effect of graphene hydroxide (GH), graphene oxide solution (GO s ), and reduced graphene oxide (rGO) on the optical properties and microstructure of metakaolin-based geopolymers. Different schemes have been proposed for preparing GH/GO/rGO geopolymers using either alkaline or phosphoric acid as the activator. The chemical composition and microstructure of kaolin and metakaolin, as well as the physicochemical and optical properties of the synthetic geopolymers, were characterized using XRD, XRF, SEM-EDS, FTIR, and UV-Vis absorbance spectroscopy. The experimental results revealed a high-purity raw kaolin with an oxide ratio of SiO 2 /Al 2 O 3 of 1.3. The incorporation of GO into the alkaline-based geopolymer matrix was confirmed by FTIR spectroscopy. According to UV-Vis results, the alkaline-based geopolymer incorporated with graphene hydroxide showed the best results. Notably, alkaline-based geopolymers displayed a higher absorbance in the visible region as well as a lower band gap energy of 2.38 eV.