Amorphous sulfur-rich CoS x nanodots as highly efficient cocatalyst to promote photocatalytic hydrogen evolution over TiO 2

In this work, amorphous cobalt sulfide with a sulfur-rich structure (sr-CoS x ) is developed as the cocatalyst for photocatalytic hydrogen evolution. Through a facile hydrothermal reaction, sr-CoS x nanodots are in situ grown on TiO 2 to obtain a heterojunction photocatalyst (sr-CoS x /TiO 2 ). The as-prepared photocatalyst exhibits remarkable improved hydrogen evolution performance compared with TiO 2. Under the irradiation of xenon lamp, the hydrogen evolution rate of sr-CoS x /TiO 2 can reach 507 μmol h −1  g −1, which is about 121 times that of pristine TiO 2, indicating that sr-CoS x is a highly efficient cocatalyst to promote hydrogen evolution on TiO 2. Moreover, sr-CoS x /TiO 2 exhibits better performance than crystalline CoS 2 or amorphous CoS modified TiO 2, suggesting the important role of sulfur-rich structure and amorphous state in promoting the cocatalytic effect. Electrochemical and photoluminescence measurements show the most efficient carrier separation between sr-CoS x and TiO 2, which also contributes to its high photocatalytic hydrogen evolution performance.