Electrochemically multi-anodized TiO2 nanotube arrays for enhancing hydrogen generation by photoelectrocatalytic water splitting

An enhanced hydrogen production by photoelectrocatalytic water splitting was obtained using extremely highly ordered nanotubular TiO2 arrays in this work. Highly ordered TiO2 nanotube arrays with a regular top porous morphology were grown by a facile and green three-step electrochemical anodization. The well ordered hexagonal concaves were uniformly distributed on titanium substrate by the first anodization, served as a template for further growth of TiO2 nanotubes. As a result, the TiO2 nanotube arrays constructed through the third anodization showed appreciably more regular architecture than that of the sample by conventional single anodization under the same conditions. The enhanced photoelectrochemical activity was demonstrated through the hydrogen generation by photoelectrocatalytic water splitting, with an exact H2 evolution rate up to 420 μmol h−1 cm−2 (10 mL h−1 cm−2) in 2 M Na2CO3 + 0.5 M ethylene glycol. The photocurrent density of the third-step anodic TiO2 nanotubes is about 24 mA cm−2 in 0.5 M KOH, which is 2.2 times higher than that of the normal TiO2 nanotubes (∼11 mA cm−2) by a single electrochemical anodization.