Highly　reduced　and　ordered　TiO2　nanotube　arrays　have　been　fabricated　using　two-step　anodization　and　three-electrode　reduction.　A　proton-electron　coupled　reduction　mechanism　has　been　proposed　based　on　the　combined　paradigms　of　a　conventional　energy-band　model　and　chemical　evolution　of　basic　building　blocks　of　TiO2.　Under　optimized　reduction　conditions,　about　22%　of　Ti4+　ions　in　tube　surface　regions　are　converted　into　Ti3+　ions　while　the　morphology　of　the　highly　reduced　TiO2　nanotube　arrays　keeps　unchanged.　The　reduced　nanotube　arrays　show　superior　electrochemical　properties　such　as　high　areal　capacitance,　good　rate　capability,　and　high　cycling　stability.　The　areal　capacitance　of　the　reduced　electrode　is　24.07　mF　cm(-2)　at　a　scan　rate　of　10　mV　s(-1),　much　higher　than　that　of　the　pristine　TiO2　nanotube　arrays　(0.02　mF　cm(-2)).　This　kind　of　highly　reduced　one-dimensional　oxide　nanostructures　can　find　a　large　array　of　applications　in　supercapacitors,　photocatalysis,　electrochromic　display,　and　Li　ion　batteries.　(C)　2015　Published　by　Elsevier　Ltd.