TiO_2 nanotube arrays semiconductor character and photoelectrocatalytic dynamics

TiO2 nanotube arrays were prepared by anode oxidation in organic electrolytes.There were different morphologies by the different oxidation time.Their photo current responses were examined with different bias applied on the Ti/TiO2 electrode.The highest photo current was indicated by the regular nanotube of 6h oxidation at the bias E=0.1V.The characteristic parameters for TiO2 nanotube arrays such as carrier density,flat potential,width of space charge layer and the badgap bending were calculated by Mott-Schottky curve and the growth mechanism of TiO2 nanotube arrays was suggested.The detailed dynamics information of TiO2 nanotube arrays electrode at the semiconductor/electrolyte interface were obtained by equivalent electrical circuit fitting to EIS spectra.The photoelectrocatalytic rate was highest at the bias potential of 0.1V.The extra bias potential can decrease the electron-transfer resistance and increase the separation efficiency of photogenerated electron-hole pairs.The redox reaction in Helmholtz layer was the rate limiting step for the photoelectron-catalytic process of ammonia degradation.