Light-induced confined growth of amorphous Co doped MoS_x nanodots on TiO_2 nanoparticles for efficient and stable in situ photocatalytic H_2 evolution

摘要

Amorphous molybdenum sulfide (a-MoSx) prepared by in situ photoreduction method with an abundance of exposed active sites has been identified as an efficient cocatalyst for catalyzing photocatalytic H-2 evolution reaction (HER). However, the intrinsic activity of the a-MoSx cocatalyst toward HER is low due to the unfavorable electronic structures of the active sites. Herein, we report a facile light-induced method for the confined growth of transition metal (TM) doped MoSx (a-TM-MoSx) cocatalysts on TiO2 nanoparticles and their catalytic activity for in situ photocatalytic HER. It is found that doping Co into a-MoSx can greatly enhance the activity of resulted a-Co-MoSx cocatalyst for photocatalytic H-2 evolution over TiO2 among the transition metal dopants (Co, Ni, Fe, Cu, Zn) tested. The most efficient a-Co-MoSx cocatalyst (Co/Mo = 1/4 and 4 mol% loading) loaded TiO2 (TiO2/a-Co-MoSx) shows a H-2 evolution rate of 133.8 mu mol h(-1), which is 3.3 times higher than that of a-MoSx loaded TiO2 (TiO2/a-MoSx). Moreover, the TiO2/a-Co-MoSx photocatalyst shows excellent recycling H-2 evolution stability. The characterization results reveal that a-Co-MoSx cocatalyst can not only effectively capture the photogenerated electrons of TiO2 to greatly enhance the separation efficiency of photogenerated charges but also significantly reduce the overpotential of HER due to the formation of highly active "CoMoS" sites, thus synergistically enhancing the catalytic activity of TiO2/a-Co-MoSx. Moreover, the light-induced growth of a-Co-MoSx on TiO2 is found to readily couple with the in situ photocatalytic HER. Therefore, this work provides a simple and efficient strategy for designing high-performance a-MoSx-based cocatalysts for stable in situ photocatalytic H-2 evolution. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.