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Highly-ordered TiO2 nanotube arrays fabricated by anodization offers high surface areas,well defined nanostructures,favorable transport pathways,and good adhesion to the substrate,and have thus become a favorable choice of electrodes for chemical and biosensors,in which the sensitivity is dependent on both surface reaction and charge transfer.Surface defects on the TiO2 nanotube electrode,including step edges,oxygen vacancies,line defects,impurities,and crystallographic shear planes have significant effects on the electrocatalytic activity,photocatalytic activity,and sensor properties.Annealing TiO2 nanotube electrode in various conditions and gases can effectively alter the crystal structure and defect concentration,thus,the electrode arrays will demonstrated appreciably different electrochemical properties.In this paper,the highly-ordered TiO2 nanotube electrodes fabricated by anodization are annealed in different gases,including O2,N2,CO2 and CO.The influence of annealing gases on the defects and surface chemistry of the TiO2 electrode was studied by means of XPS,XRD and SEM.The influence of surface defects and carbon-doping on the electrochemical properties of TiO2 nanotube electrode were also investigated and discussed.This fundamental research work will create a precedent in the field of a novel structure of modified electrode for biosensor,electroanalysis and electrocatalysis.