A　simple　one-step　method　to　prepare　graphene　nanoribbon　(GNR)　is　reported　in　this　paper.　Compared　with　water　steam　etching,　the　oxidation　and　co-etching　of　dilute　sulfuric　acid　can　result　in　the　more　complete　longitudinal　unzipping　of　carbon　nanotube,　although　there　is　no　other　strong　oxidant.　As-prepared　GNRs　are　more　flat　and　have　more　oxygenated　functional　groups　along　the　edge.　Moreover,　they　can　steadily　disperse　in　a　water　system.　These　make　them　suitable　as　a　carrier　for　supporting　palladium　(Pd)　nanoparticles.　The　Pd/GNR　composite　exhibits　a　superior　electrocatalytic　activity　for　ethanol　oxidation.