A　simple,　clean　method　of　steam　etching　carbon　nanotubes　is　reported　for　the　synthesis　of　graphene　nanoribbons.　The　chemical　mechanism　of　carbon　nanotube　unzipping　is　also　discussed.　As　an　anode　catalyst,　as-prepared　graphene　nanoribbons　combined　with　Pt　exhibit　quite　a　high　catalytic　activity　for　ethanol　electro-oxidation　in　fuel　cells.