▎ 摘　　要

NOVELTY - Preparing graphene oxide, involves (i) heating flake graphite in tubular furnace under protection of argon at 1000 degrees C for 2 hours to obtain expanded graphite, (ii) adding 7.7 g expanded graphite to 2000 ml beaker, adding 900 ml concentrated sulfuric acid, 100 ml phosphoric acid and 50 g potassium permanganate, where volume ratio of sulfuric acid to phosphoric acid is 9:1, and stirring until color of the solution is green, (iii) stirring and reacting mixture in water bath at 50 degrees C for 5 hours which gradually changes color of the solution from green to brown, (iv) pouring brown solution to 1000 ml ice water containing 100 ml hydrogen peroxide (30%) and stirring which changes color of the solution to golden brown, (v) leaving still overnight, discarding supernatant and centrifuging lower solution at 9500 rpm, and (vi) washing with 10% dilute hydrochloric acid to remove sulfate ions and unreacted graphite, washing with distilled water until pH is 5, and collecting brown viscous product. USE - The method is useful for preparing graphene oxide. ADVANTAGE - The method improves the strength of graphene sponge.