Research On The Preparation And Hydrogen Evolution Application Of ?-Mo₂/CdS Composite Photocatalyst

Now,the energy shortage and environmental pollution have become important factors in social development.Photocatalytic water-splitting technology can effectively solve these problems.But now photocatalytic activity is not efficient.One of the main reasons is the photo-generated electrons and holes are not well separated.Loading cocatalyst can effectively improve the separation of electrons and holes,suppress the recombination,thereby improve the photocatalytic efficiency.But most of the traditional noble metal co-catalysts are not suitable for industrial applications.Development of non-precious metal co-catalysts therefore is important.In this paper,?-Mo2N/CdS composite photocatalyst was prepared as follows:(1)Pure phase y-Mo2N was prepared.Firstly,H2MoO4 as molybdenum source was dissolved in NH3·H2O to form ammonium molybdate solution.After the solution was evaporated to dryness,the solid was calcined in a muffle furnace,and MoO3 was prepared.Then MoO3 was calcined in nitrogen atmosphere,and?-Mo2N was prepared.(2)?-Mo2N/CdS composite photocatalyst was prepared,A certain amount of?-Mo2N was ultrasonic dispersed in(CH3COO)2Cd solution,and Na2S solution was dropped dropwise,then yellow-green precipitate was formed.After that,the precipitate was filtered,washed and dried in vacuum oven,and ?-Mo2N/CdS composite photocatalyst was prepared.The composite photocatalysts were characterized and tested,and following conclusion was obtained:(1)XRD characterization results showed that pure phase of y-Mo2N was successfully obtained.(2)By SEM and TEM,we found that ?-Mo2N and CdS formed a structure which is similar to core-shell structure,and CdS wrapped on the outside of ?-Mo2N.(3)XPS characterization result obtained showed that little part of Mo on the surface of ?-Mo2N existed in the form of MoO2 and MoO3.(4)UV-visible diffuse reflectance spectroscopy characterization results showed the absorbance of ?-Mo2N/CdS composite photocatalyst in the visible region was larger than CdS.(5)The hydrogen production activity of the optimum ?-Mo2N/CdS composite photocatalyst(2%loading,800 ?nitrided),under visible light conditions,reached 970 ?mol/(h·g),is 6 times of CdS,1.5 times of Pt/CdS.Thus,it was confirmed that ?-Mo2N performed like Pt in photocatalysis as cocatalyst.In this paper,grapheme(GR)based Mo2N-Mo2C/CdS composite photocatalyst was prepared as follows:(1)Mo2N-Mo2C/GR was prepared.MoCls,as molybdenum source,urea,as carbon and nitrogen source,and graphite oxide,as precursor of grapheme,was added in ethanol.After the excess ethanol was evaporated,the complex was calcined in nitrogen,and Mo2N-Mo2C/GR was prepared.(2)Mo2N-Mo2C/GR/CdS composite photocatalyst was prepared.A certain amount of Mo2N-Mo2C/GR was ultrasonic dispersed in(CH3COO)2Cd solution,and Na2S solution was dropped dropwise,then yellow-green precipitate was formed.After that,the precipitate was filtered,washed and dried in vacuum oven,and Mo2N-Mo2C/GR/CdS composite photocatalyst was prepared.The composite photocatalysts were characterized and tested,and following conclusion was obtained:(1)XRD characterization results showed that different Mo complex,such as Mo2N,Mo2C and Mo2N-Mo2C was obtained via controlling the amount of urea.(2)By SEM and TEM,we found that Mo2N-Mo2C and CdS were dispersed on the surface of grapheme.(3)XPS characterization result obtained showed that little part of Mo on the surface of Mo2N-Mo2C existed in the form of MoO2 and MoO3.(4)UV-visible diffuse reflectance spectroscopy characterization results showed that GR,Mo2N,Mo2C and Mo2N-Mo2C improved the absorbance of CdS in the visible region.(5)The hydrogen production activity of Mo2N-Mo2C/GR/CdS composite photocatalyst reached 4520?mol/(h·g),is 18 times of CdS,7 times of GR/CdS,1.7 times of Mo2N/CdS,1.4 times of Mo2C/CdS,1.3 times of Mo2N-Mo2C/CdS,1.2 times of Mo2N/GR/CdS and 1.1 times of Mo2C/GR/CdS.