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.