A photoelectrochemical investigation of the hydrogen-evolving doped TiO2 nanotube arrays electrode

The present work investigates the photoelectrochemical behavior of nanotubular N/C-TiO2 electrode for hydrogen production. Via the sonoelectrochemical anodization process of 1 h, N-containing TiO2 based nanotube arrays(N-TNT) with the length of about 650 nm were fabricated in fluoride aqueous solution added 0.25 M NH4NO3; C-containing TiO2 based nanotube arrays(C-TNT) with the length of about 2 μm were prepared in fluoride ethylene glycol solution. In virtue of the longer tubes with the larger surface areas, C-TNT can harvest more light and produce more photoactive sites than N-TNT, which also made the charge transfer resistance in C-TNT larger than that in N-TNT. Considered the more negative flat band potential of C-TNT, C-TNT has the smaller energy barrier and the better photoelectrochemical activity. It may be attributed to the appropriate defect concentration gradient owing to the modification of C element. Under UV–vis light (320–780 nm) irradiation, the average hydrogen generation rate of C-TNT was 282 μL h−1 cm−2. The surface properties and near-surface properties of the resultant electrode were synthetically analyzed by using UV–vis diffuse reflectance spectra(DRS), field emission scanning electron microscopy (FESEM), I-t curves, and electrochemical impedance spectroscopy (EIS) techniques.

► N-containing TiO2 nanotube arrays were anodized in fluoride aqueous solution.
► C-containing TiO2 nanotube arrays were anodized in ethylene glycol solution.
► Flat band potential of C-TNT is more negative than that of N-TNT.
► The appropriate defect concentration gradient may be created by doping C element.
► C-TNT exhibited the better surface properties and near-surface properties.