Chloranil

Quinones (chloranil and dichloroanthraquinone (DCAQ)) were purchased from Tokyo Chemical Industry Co., Ltd., and activated carbon (MAXSORB) was purchased from Kansai Coke and Chemicals Co., Ltd. We purchased chloranil instead of TCHQ because chloranil is more stable in air than tetrachlorohydroquinone (TCHQ) and is hence more inexpensive. They were used as received without further purification. Active materials impregnated with chloranil (3 g) and DCAQ (3 g) were dissolved in 1.5 and 3 L of acetone, respectively, and sonicated for 10 min. Activated carbon (7 g) was dispersed in the solution via sonication for 1 h. The solution was stirred at 80 °C to evaporate acetone, and quinones were impregnated into the nanopores of the activated carbon. The obtained powder was mixed with a polytetrafluoroethylene (PTFE) binder at a weight ratio of 9:1, and the pellet was then formed. Notably, a conductive additive was not used. Therefore, the weight ratio of the electrode is as follows; quinone: activated carbon: PTFE = 27:63:10.

Benzaldehyde-2-sulfonic acid sodium salt (BS), chloranil, 2-methylresorcinol (2,6-dihydroxytoluene) (DHT), and 2,4,6-trihydroxybenzaldehyde (THBA) were purchased from Tokyo Chemical Industry (Tokyo, Japan). Pyrrole (Pyr), pyrogallol (1,2,3-trihydroxybenzene, THB), acetyl chloride, triethylamine, p-toluenesulfonic acid monohydrate (p-TS), tetrabutylammonium hexafluorophosphate, acetonitrile, and phosphate buffer were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). The Pyr monomer was purified via distillation prior to use.

4-formylbenzoic acid, 3-(N,N-dimethylamino)phenylboronic acid, acetic acid (glacial), boron trifluoride-diethyl ether complex (BF₃·Et₂O), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) were obtained from Sigma-Aldrich Japan (Tokyo, Japan); D-fructose (Fru) and D-glucose (Glc) were obtained from FUJIFILM Wako Pure Chemical Corp. (Osaka, Japan); chloranil was obtained from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan); and cresyl violet (fluorescence reference standard) was obtained from Cosmo Bio Co., Ltd. (Tokyo, Japan). All chemicals were used without further purification.