The　use　of　TiO2　nanotube　arrays　fabricated　by　anode　oxidation　of　titanium　sheets　as　a　photoelectrocatalyst　is　limited　by　low　surface　activity　owing　to　passive　crystallization　post-treatment.　We　report　here　on　a　vacuum　assisted　filling　route　for　modifying　TiO2　nanotube　arrays　using　high-activity　anatase　TiO2　nanoparticles　as　a　filling.　Photoelectrocatalytic　degradation　experiments　show　that　a　nearly　4-fold　activity　enhancement　in　photoelectrocatalysis　is　achieved　and　good　photoelectrocatalytic　stability　is　kept　after　the　nanotube　arrays　are　filled　with　the　high-activity　TiO2　nanoparticles.　The　remarkable　enhancement　in　photoelectrocatalysis　is　ascribed　to　the　key　modification　of　the　TiO2　nanotube　arrays　using　the　high-activity　TiO2　nanoparticles.　Our　findings　provide　an　insight　into　designing　excellent　photoelectrocatalysts　by　filling　TNAs　with　available　high-activity　TiO2　nanoparticles.　(C)　2011　Elsevier　B.V.　All　rights　reserved.