On the photocatalytic and electrocatalytic hydrogen evolution performance of molybdenum sulfide supported on TiO2

Abstract

This study aimed to define key preparation and treatment parameters determining the hydrogen evolution reaction (HER) performance of molybdenum sulfide-based photocatalysts. Amorphous and nanocrystalline molybdenum sulfide catalysts supported on titania have been studied in photocatalytic and electrochemical HER. The results of HER measurements were compated to the thiophene hydrodesulfurization HDS activity. Titania polymorph plays a crucial role for HER: high-surface area anatase PC500 and anatase-rutile Degussa P25 show high HER performance, whereas rutile nanorods demonstrate poor activity. Two preparation methods applying impregnation and solution deposition techniques have been compared. Solution deposition affords superior activity, with a maximum HER rate for 0.5%wt. Mo loading, even if the dispersion of MoS2 phase and HDS activity are better for impregnated systems. Therefore, for the photocatalytic performance not the dispersion of MoS2 and abundance of edge sites but efficient electron hopping from the semiconductor to the co-catalyst is most important. In order to study the influence of the MoS2 edges state, the solids reduced under H2 or treated in pure H2S were compared. The presence edge S22− groups have a positive influence on the photo- and electrocatalytic HER activity.