Photo and photoelectrochemical properties of p-type low-temperature dehydrated nanotube titanic acid

Nanotube titanic acid (H2Ti2O5 · H2O, NTA) is thermally unstable. Its low-temperature (100–300 °C) dehydrated product (LD-NTA) possesses a symmetrical ESR signal with a g = 2.003, which is the characteristic of a single-electron-trapped oxygen vacancy (SETOV). High concentration SETOV defects can form a sub-band within the bandgap (Eg) of LD-NTA and exhibit a response to visible light. Each SETOV possesses one effective positive charge. Under visible light irradiation, the working electrode prepared from LD-NTA shows a p-type Iphoto–Vbias behavior (Iphoto = photocurrent, Vbias = bias potential), which suggests that SETOV in LD-NTA plays the role of major positive carriers, like h+.