2 propanol

Using the synthesized samples as active electrode materials, the electrocatalytic activity for the ORR was evaluated using a dual electrochemical analyzer (ALS704ES, BAS). The carbon material (5 mg) was added to a mixed solution consisting of 950 µL of 2-propanol (Kanto Chemical Co., Tokyo, Japan, >99.7%) and 50 µL of Nafion perfluorinated resin solution (Sigma-Aldrich, St. Louis, MI, USA), which was then dispersed by ultrasonic stirring for 10 min to prepare a slurry. The prepared slurry (7.5 µL) was added dropwise to a Pt-GC electrode, which was then dried under atmospheric pressure overnight and used as a working electrode. An Ag/AgCl electrode in saturated aqueous KCl solution and a Pt electrode were used as the reference and counter electrodes, respectively. A 0.1 M aqueous KOH solution was used as the electrolyte. Linear sweep voltammetry (LSV) and chronoamperometry (CA) measurements were performed in an oxygen-saturated environment using a rotating ring-disk electrode device (RRSE-3A, BAS, manufacturer, Tokyo, Japan). LSV data were acquired at a rotational speed of 1600 rpm and a scan speed of 10 mV/s in the scan range of 0 to −1 V vs. Ag/AgCl. In this study, all potentials were converted to the reversible hydrogen electrode (RHE) standard using the following equation:
CA data were acquired for 20,000 s at a rotation speed of 1600 rpm and a potential of 0.45 V (vs. RHE).

Inhibitors were removed from methyl acrylate (MA, > 99.0%, Tokyo Chemical Industry), ethyl acrylate (EA, > 99%, Nakalai Tesque), 1H,1H,2H,2H-perfluorododecyl acrylate (C₁₀F₂₁A, 97%, Apollo Scientific), 1H,1H,2H,2H-heptadecafluorodecyl acrylate (C₈F₁₇A, > 97.0%, Tokyo Chemical Industry), 2-(perfluoro-9-methyldecyl)ethyl acrylate (C₁₁F₂₃A, 97%, Apollo Scientific), and 1,9-bis(acryloyloxy)nonane (> 92.0%, Tokyo Chemical Industry) using aluminum oxide (activated, Kanto Chemical) before use. Benzoyl peroxide (BPO, containing 25 wt% water, Nakalai Tesque) was purified via recrystallization using Drysol N (ethanol 88%, methanol 3%, 2-propanol 9%, Kanto Chemical). Toluene (> 99.5%, Kanto Chemical), n-hexane (> 96.0%, Kanto Chemical), tetrahydrofuran (THF, > 99.5%, Kanto Chemical), acetone (> 99.5%, Kanto Chemical), methanol (> 99.8%, Kanto Chemical), hydrochloric acid (35%, Nacalai Tesque), CDCl₃ (99.8%, Nacalai Tesque), sodium hydroxide (NaOH, 97%, Nakalai Tesque), and 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (> 98.0%, Tokyo Chemical Industry) were used without further purification. A chemically crosslinked silicone elastomer block was obtained from Tigers Polymer Co.

Oil-red O powder (Sigma-Aldrich, St. Louis, MO, USA) was dissolved in 0.5% 2-propanol (Kanto Chemical, Tokyo, Japan). The stock was then diluted to a 0.3% Oil-red O solution with distilled H₂O and filtered through a 0.22-μm filter. Frozen sections (20 μm thick) of fish muscle sample were fixed with 2% paraformaldehyde and 2% glutaraldehyde (Sigma-Aldrich) in 0.1 M phosphate buffer (pH 7.4) for 10 min at room temperature. After fixation, sections were washed with phosphate buffer three times and stained with 0.3% Oil-red O solution for 10 min at room temperature. Finally, stained sections were washed with phosphate buffer three times, mounted with aqueous mounting medium, and sealed with nail polish. Sections were examined with an Olympus BH-2 light microscope (Tokyo, Japan).