The　effect　of　H2O　contents,　from　2%　to　30　vol%,　in　an　ammonium　fluoride/ethylene　electrolyte　on　the　field　emission　property　of　anodized　TiO2　nanotubes　was　investigated.　The　morphology　and　composition　of　the　samples　were　characterized　by　scanning　electron　microscopy　(SEM)　and　X-ray　photoelectron　spectroscopy　(XPS),　respectively,　which　were　relatively　independent　of　the　H2O　content　in　the　electrolyte.　The　porous　TiO2　films　were　produced　at　low　H2O　content　of　2-10　vol%　due　to　slow　chemical　dissolution,　and　were　mainly　composed　of　TiO2　center　dot　nH(2)O　complex.　Moreover,　the　well-aligned　TiO2　nanotubes　were　grown　at　moderate　H2O　content　of　15　vol%　with　a　little　TiO2　center　dot　nH(2)O　complex.　However,　with　increasing　H2O　content　to　20-25　vol%,　nanotube　clusters　of　TiO2　with　enlarged　inter-cluster　distance　and　sharp　tops　of　each　nanotube　in　clusters　were　formed　due　to　electric　field　induced　dissolution.　The　optimal　turn-on　field　for　electron　field　emission　of　TiO2　nanotubes　was　obtained　as　low　as　1.9　V/mu　m.　It　was　suggested　that　the　reduced　local　field　screening　effect　could　significantly　contribute　to　the　improved　field　emission　property　of　TiO2　nanotubes.　(C)　2014　Elsevier　B.V.　All　rights　reserved.