Highly active titanium oxide photocathode for photoelectrochemical water reduction in alkaline solution

Developing low-cost, efficient and stable metal oxide cathode catalyst for hydrogen evolution reaction (HER) is of great importance to overcome the major challenge in photoelectrochemical water splitting (PECWS) cell. Anodic titanium dioxide nanotube (TNT) as the electrode has shown promising for its flexibility, economy and efficiency. Herein, a highly active and stable photocathode for HER was achieved with a technique of stepwise cathodic reduction of anodic TNT without loading any cocatalyst. It exhibits a self-improving PECWS performance after the five-step cathodic reduction process. The onset voltage displays an anodic shift from −0.79 to 0.19 V versus the reversible hydrogen electrode (RHE) and the overall current shows an enhancement from −110.06 to −210.66 mA at −1.0 V_RHE in 1 M NaOH aqueous solution (pH = 13.6). The photocathode also withstands a voltage @ −1.0 V_RHE and a current @ −100 mA in the WS cell for more than 12,000 s sequentially. This work demonstrates a feasible strategy for forming a multijunction composite for efficient HER with the anodic TNT as the precursor.