Amorphous sulfur-rich CoS_x nanodots as highly efficient cocatalyst to promote photocatalytic hydrogen evolution over TiO_2

摘要

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.