title: Exfoliation of graphite into graphene in aqueous solutions of inorganic salts.
abstract: Mass production of high-quality graphene sheets is essential for their practical application in electronics, optoelectronics, composite materials, and energy-storage devices. Here we report a prompt electrochemical exfoliation of graphene sheets into aqueous solutions of different inorganic salts ((NH4)2SO4, Na2SO4, K2SO4, etc.). Exfoliation in these electrolytes leads to graphene with a high yield (>85%, ≤3 layers), large lateral size (up to 44 μm), low oxidation degree (a C/O ratio of 17.2), and a remarkable hole mobility of 310 cm(2) V(-1) s(-1). Further, highly conductive graphene films (11 Ω sq(-1)) are readily fabricated on an A4-size paper by applying brush painting of a concentrated graphene ink (10 mg mL(-1), in N,N'-dimethylformamide). All-solid-state flexible supercapacitors manufactured on the basis of such graphene films deliver a high area capacitance of 11.3 mF cm(-2) and an excellent rate capability of 5000 mV s(-1). The described electrochemical exfoliation shows great promise for the industrial-scale synthesis of high-quality graphene for numerous advanced applications.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany.
authors.forename: Khaled
authors.initials: K
authors.lastname: Parvez
authors.forename: Zhong-Shuai
authors.initials: ZS
authors.lastname: Wu
authors.forename: Rongjin
authors.initials: R
authors.lastname: Li
authors.forename: Xianjie
authors.initials: X
authors.lastname: Liu
authors.forename: Robert
authors.initials: R
authors.lastname: Graf
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen