Preparation Of Nanosheet Cu₂WS₄ Photocatalysts And Hydrogen Production Research

In this paper,visible light response nanosheet C u2WS4 photocatalysts were prepared by mixed solvthermal method at low temperature without surfactant required.In order to explore the effect of phase composition,morphology and light-absorbing properties on the hydrogen production activity,the synthesized samples were characterized by XRD,XPS,SEM,UV-vis,TEM,Mott-Schottky measurement and hydrogen production performance test.The samples were then tested by PL and photocurrent test,exploring the effect of different reaction temperature and reaction time on the carrier recombination rate and migration rate of nanosheet C u2WS4 photocatalyst and the relationship between these factors and hydrogen production performance.Typical synthesis nanosheet C u2WS4 photocatalysts are as follows: 2.5 mmol sodium tungstate dihydrate?Na₂WO₄·2H2O?,5 mmol cuprous chlorides?C uC l?and thioacetamide?C H3CSNH2?were dispersed into the mixed solvents containing 15 mL deionized water?H2O?and 15 mL ethanol?C2 H5OH?with continuous stirring.Then the dispersion was transferred into a Teflon-lined steel autoclave?50 mL?,and remained at 120 °C for 24 h.The experimental results show that the highly crystalline C u2WS4 photocatalyst prepared by mixed solvothermal method had the morphology of two-dimensional nanosheets with uniform particle size distribution,which contributed to the effective separation and rapid transport of char ge carries.Thus the photocatalytic activity of photocatalyt ic decomposition of water for hydrogen production of Cu₂WS₄ photocatalysts was improved significantly.Under the visible light irradiation??>400nm?,the effects of different solvent components,ultrasonic time,ratio of sacrific ial agents and the amount of catalyst on the performance of nanosheet C u2WS4 photocatalysts were investigated.The optimal synthesis conditions were that,raw materials?the molar ratio of C u,W andS to be 2:1:5?with 15 mL ethanol and 15 m L deionized water were treated at 120 oC for 24 h.O n the other hand,the reaction parameters for hydrogen production by water splitting was determind as that amount of photocatalyst s was 15 mg,concentration of Na2 S is 0.35 mol·L-1,concentration of N a2SO3 was 0.25 mol·L-1,ultrasonic dispersion time was 30 minutes.The nanosheet C u2 WS4 photocatalyst shows the best hydrogen production rate?0.422 mmol·h-1·g-1?.In order to assess the photocatalyt ic stability of C u2WS4 nanosheets,4 cycles for a period of 4 h were measured.It was illustrated that the hydrogen production rate of sample still remained up to 0.395 mmo l·h-1·g-1 and no noticeable deactivation was detected after 16 h of constant irradiation,suggesting relative ly high stability of the C u2WS4 nanosheets for H2 evolution.Cu₂WS₄/CdS was synthesized by two steps solvothermal method.The optimum CdS composite content was investigated by characterization of the sample.The effects of C dS composite on the morphology,crystal structure and hydrogen production of C u2WS4 were discussed.The study found that CdS particles with a particle size of less than 10 nm adhered to the surface of C u2WS4 nanosheets to realize the composite of CdS and C u2WS4.The compound of CdS was not affect the crystal structure of nanosheet C u2WS4,while C u2WS4 /15%CdS had the best hydrogen production p erformance,reaching 0.98 mmol·h-1·g-1,which was 2.2 times that of pure C u2 WS4.In combination with PL and I-T,it was analyzed that the formation of p-n junction by CdS and C u2WS4 contributed to the effective separation and rapid transport of charge carries,thus the photocatalytic hydrogen production performance of this material was significantly improved.