Reduced TiO2 nanotube array as an excellent cathode for hydrogen evolution reaction in alkaline solution

Anodic TiO2 nanotube (TNT) arrays have been intensively investigated as anodes in water splitting (WS) cells because of their excellent chemical stability. However, anodic TNT is seldom considered as a cathode for the hydrogen evolution reaction (HER) in an electrochemical WS cell. This study shows that a reduced TNT (R-TNT) sample prepared with a cathodic reduction technique without loading any co-catalyst can achieve remarkable HER performance. At -1.0 V vs reversible hydrogen electrode in 1 M NaOH in dark, R-TNT achieved a current of -221 mA, which is 17000-times of that achieved when using TNT and 5-times of that with Ti-foil as cathode. Chronopotentiometry tests were carried out sequentially at @-100, -50 and -10 mA for 24 h and decay rates of 1.3%, 5.2% and 18.4% were measured, which indicate a good stability of the R-TNT sample.