Amorphous sulfur-rich CoSx nanodots as highly efficient cocatalyst to promote photocatalytic hydrogen evolution over TiO2

In this work, amorphous cobalt sulfide with a sulfur-rich structure (sr-CoSx) is developed as the cocatalyst for photocatalytic hydrogen evolution. Through a facile hydrothermal reaction, sr-CoSx nanodots are in situ grown on TiO2 to obtain a heterojunction photocatalyst (sr-CoSx/TiO2). The as-prepared photocatalyst exhibits remarkable improved hydrogen evolution performance compared with TiO2. Under the irradiation of xenon lamp, the hydrogen evolution rate of sr-CoSx/TiO2 can reach 507 μmol h−1 g−1, which is about 121 times that of pristine TiO2, indicating that sr-CoSx is a highly efficient cocatalyst to promote hydrogen evolution on TiO2. Moreover, sr-CoSx/TiO2 exhibits better performance than crystalline CoS2 or amorphous CoS modified TiO2, 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-CoSx and TiO2, which also contributes to its high photocatalytic hydrogen evolution performance.