The Synthesize And Improvement Of Photocatalytic Activity Of G-C₃N₄and CdS

Since Fujishima and Honda discovered the photocatalytic splitting of water onTiO2electrodes in1972, a large number of investigations have focused on thesemiconductor photocatalysts for its wide applications in solar energy conversions andenvironmental purification. Among various photocatalysts, g-C3N4(2.7eV) and CdS(2.4eV) can produce hydrogen from water splitting, which has draw lots of interests.In a typical synthesis, g-C3N4is firstly prepared by heating melamine (6g) at550℃for4h in argon (Ar) atmosphere, and then MoS2-g-C3N4(4wt%of MoS2) isprepared by the solvothermal reaction of Na2MoO4(20mg) H2NCSNH2(100mg) andas-prepared g-C3N4(500mg) in ethylene glycol (25mL) at200℃for20h.3CdSO4.8H2O (1.8g) and C2H5NS (1g) were added to distilled water, after about20minof ultrasound, the solution was then transferred into a Teflon-lined stainless steelautoclave. The autoclave was sealed, heated and maintained at200℃for12h. Then, itwas then allowed to cool down to room temperature naturally. After that, the productwas collected by centrifugation, washed with distilled water and dried in an oven at90℃for6h. Nb2O5-CdS composite photocatalysts were prepared as follows: The Nband as-prepared CdS powders were grounded together with the weight ratio value ofNb2O5to CdS fixing at0.5, then the resultant samples were collected and calcined at400℃for3h in a muffle furnace. The obtained samples were labeled as N0.5C. Forcomparison, the weight ratios of Nb2O5to CdS with the values fixing at0,0.25,1and2were also synthesized as the above method and labeled as CdS, N0.25C, N1C and N2C,respectively. The MoS2-g-C3N4composite photocatalyst showed high photocatalytic H2production activity with a rate as high as16.592μmol/h for the sample containing4wt%MoS2as cocatalyst, which is about9.67folds than that of pure g-C3N4. A possiblephotocatalytic mechanism is also proposed based on the experiment results, theenhanced photocatalytic activity can be attributed to the reason that MoS2as a cocatalyst can efficientlysuppress charge recombination, improve interfacial charge transfer, provide morephotocatalytic reaction centers. In the Nb2O5-CdS system, a low amount of Nb2O5candramatically improve the photocatalytic activity and the optimal weight ratio values ofNb2O5to CdS was fixing at0.5, which resulted in a high visible-light photocatalyticH2-production rate of43.5μmol/h and is about4folds than that of pristine CdS...