title: Coal Oxide as a Thermally Robust Carbon-Based Proton Conductor.
abstract: Inexpensive solid proton conducting materials with high proton conductivity and thermal stability are necessary for practical solid state electrochemical devices. Here we report that coal oxide (CO) is a promising carbon-based proton conductor with remarkable thermal robustness. The CO produced by simple liquid-phase oxidation of coal demonstrates excellent dispersibility in water owing to the surface carboxyl groups. The proton conductivity of CO, 3.9 × 10(-3) S cm(-1) at 90% relative humidity, is as high as that of graphene oxide (GO). Remarkably, CO exhibits much higher thermal stability than GO, with CO retaining the excellent proton conductivity as well as the capacitance performance even after thermal annealing at 200 °C. Our study demonstrates that the chemical modification of the abundant coal provides proton conductors that can be used in practical applications for a wide range of energy devices.
authors.affiliation: Graduate School of Science and Technology, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Hatakeyama
authors.affiliation: Graduate School of Science and Technology, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Ogata
authors.affiliation: Graduate School of Science and Technology, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Koinuma
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: Graduate School of Science and Technology, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Hayami
authors.affiliation: Department of Nanoscience Faculty of Engineering, Sojo University , 4-22-1 Ikeda, Nishi-ku, Kumamoto 860-0082, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Kuroiwa
authors.affiliation: Graduate School of Science and Technology, Kumamoto University , 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan.
authors.forename: Yasumichi
authors.initials: Y
authors.lastname: Matsumoto
keywords: carbon material; coal; proton conduction; solid state electrolyte; thermal stability