Photoelectrochemical characterization of TiO2 nanotube array for ammonia degradation by electrochemical impedance spectroscopy

Well-ordered TiO2 nanotube arrays are prepared by the electrochemical anodization on pure Ti surfaces in organic solution. TiO2 nanotube arrays have good photo response by the photocurrent tests. Photoelectrochemical characteristics of the TiO2 nanotube arrays are investigated by electrochemical impedance spectroscopy (EIS) in the ammonia degradation cell system. The extra bias potential can decrease the values of the electron-transfer resistance and increase the separation efficiency of photogenerated electron-hole pairs. The photoelectrocatalytic rate is highest at the bias potential of 0.1V. The detailed dynamics information of TiO2 nanotube arrays electrode concerning the double charged layer at the semiconductor/electrolyte interface are obtained by equivalent electrical circuit fitting to EIS spectra. The results reveal that the surface reaction step is the rate limiting step for the photoelectron-catalytic process of ammonia degradation.