Photocatalytic Hydrogen Production Of Molybdenum Sulfide And Its Composite

Solar-driven photocatalytic hydrogen production by water splitting is one of the hot research topic in recent years.Molybdenum sulfides can be widely regarded as the most potential catalysts to replace Pt-group metals because of its excellent hydrogen evolution activity,low cost,non-toxic.However,their reaction activity is restricted by high recombination rate of the photogenerated carriers,low mobility and conductivity.In response to these problems,we focus on increasing the active site,extending light response range and promoting separation efficiency of electron-hole.Specifically,our work involves the following aspects:?1?Amorphous MoS₃ was successfully synthesized via simple and easy wet chemistry method by the reduction of?NH4?2MoS₄ with NH2OH·HCl at low temperature and was characterized by a series of techniques.The maximal hydrogen evolution rate achieved 1190.0 ?mol·h-1 by using Erythrosin B?EB?as photosensitizer and triethanolamine?TEOA?as sacrificial reagent under the optimal conditions.In addition,the stabilities of MoS₃ and EB-MoS₃ system were also evaluated.The results indicated that gradual composition change from MoS₃ to MoS₂ occurred during the H2 evolution process and the amorphous MoS₂ formed was the actual active species for H2 evolution.However,extensive investigations showed that except for the photodegradation of EB,activity decrease of catalyst in the long-term determination and recycling test should mainly originate form the occupation of its surface active sites by some other species in the reaction mixture.?2?MoS_2+x materials were prepared by annealing amorphous MoS₃ at diffenert temperature and were proven by a series of characterization.The noble-metal-free photocatalytic hydrogen production system was constructed with MoS_2+x as catalyst,EB as photosensitizer and TEOA as sacrificial reagent.The results indicated that the composition,morphology,crystallinity,specific surface area of catalysts changed at different calcination temperature.The calcination temperature greatly affected the hydrogen-evolving activity.Under the same condition,300-MoS_2+x catalyst exhibited much higher hydrogen evolution performance than other catalysts.The factors affecting its H2-evolving performance were investigated in details and the maximal hydrogen evolution rate of 1923.5 ?mol·h-1 was achieved under optimal conditions.Meanwhile,the activity decrease of catalyst mainly originates form photodegradation of EB and occupation of surface active sites.?3?MoS₂-NiS/CdS composite was synthesized by three-step hydrothermal method and was characterized by a series of techniques.The noble-metal-free photocatalytic hydrogen production system was constructed with Cd S as solid photosensitizer,MoS₂ and NiS as cocatalysts,lactic acid as electron donor.It showed good stability and excellent photocatalytic performance with the H2 evolution rate about 2525.2 ?mol/h in lactic acid solution under visible light irradiation.