Topotactic conversion of calcium carbide to highly crystalline few-layer graphene in waterElectronic supplementary information (ESI) available: Further details of FLG synthesized using LiOH, acetic acid, ethylene glycol, and AgNO3/NMP solution, including SEM images, XRD profiles, and Raman spectra. See DOI: 10.1039/c8ta08632j

• Main Authors: Jia, Yin, Chen, Xiangchao, Zhang, Guoxin, Wang, Lin, Hu, Cejun, Sun, Xiaoming
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta08632j

The reaction of calcium carbide (CaC 2 ) with water to produce acetylene is common in industrial production, but its side reaction, removal of calcium from CaC 2 (also termed de-Ca) to fabricate highly graphitic carbon, is highly overlooked. Herein, we report the synthesis of highly crystalline few-layered graphene by controlling the reaction of tetragonal-phased CaC 2 with water at room temperature (20-25 °C). The resulting carbon materials were revealed to be highly graphitic, with ∼3 nm thickness, containing >93 at% carbon. Raman spectroscopy evidenced their low defect content with a defect (D)/graphitization (G) ratio of ∼0.07. HRTEM further verified their high graphitization degree. A formation mechanism was proposed: the C 2 2− dumbbells donate their electrons to nearby oxidative species, e.g. H + in water, followed by topotactic cross-linking to form a conjugated sp 2 -carbon network. Furthermore, the capability of CaC 2 reduction and re-assembly into graphitic carbon was clearly evidenced by reaction with Ag + in non-aqueous solvent, which resulted in a larger quantity of graphene materials and small-sized Ag nanoparticles. CaC 2 redox-reaction with water facilitates the formation of highly crystalline graphene via the electron depletion and cross-linking of pre-arranged C 2 2− dumbbells.