Fabrication And Photocatalytic Hydrogen Production Of CdS-based Nanocomposites

Considering the energy crisis and environment issues caused by the burning of fossil fuels,splitting of water to H2 by photocatalysis technology has attracted great attention.Hydrogen,as a renewable and eco-friendly energy,is considered as one of the most attractive candidate in place of fossil fuels.Semiconductor photocatalysis has been widely used in solar hydrogen production and photodegradation of organic contaminant.The traditional photocatalytic materials,such as Ti O2,WO3 and Zn O,can only absorb UV light(accounts for only 4% of the solar energy)due to the large bandgap,thus hinder their widespread application in photocatalytic water splitting.Recently,transition-metal chalcogenides have attracted ever-growing attention due to their unusual optical and electric properties.Among them,n-type Cd S has been one of the most studied materials because of its narrow band gap(2.4 e V)for valid absorption of visible light and the proper conduction band edge for H+/H2 redox potential.However,Cd S shows an extremely low activity for the photocatalytic H2 production and low stability resulting from the serious electron-hole pairs recombination and photocorrosion.The purpose of this thesis is to improve the visible light utilization,reduce the recombination rate of photoelectrons and holes,make the photogenerated carriers participate in the redox reaction as much as possible and improve the photocatalytic efficiency with the introduction of co-catalyst during the third step of processes in photocatalytic water splitting.The morphology,crystal phase,and unique photoelectrical properties of obtained samples were characterized by XRD,TEM,SEM,UV-vis,and XPS.The main contents of this thesis are as follows:(1)In present work,Cd S loaded with Pt was successfully prepared by a solvothermal method followed annealing treatment,the composites exhibit enhanced hydrogen evolution activities compared with those of the materials obtained from the traditional approaches,such as photodeposition.The effects of different sacrificial reagents and calcination temperature on the hydrogen evolution activities were systematically investigated.The results show that the Pt-Cd S-500 displayed the maximum H2 generation rate of 10.3 mmol h-1 g-1 with lactic acid as sacrificial agents,which is 25.0 and 2.0 times higher than that of Cd S(0.4 mmol h-1 g-1)and Pt-Cd S-PR(1 wt% Pt),respectively.(2)The Cd S nanospheres with rough surface modified by ultrathin Mo S2 nanosheets have been successfully constructed by “two-step hydrothermal growth” route for Pt-free photocatalytic hydrogen production.The effects of different sacrificial reagents and loading amounts of Mo S2 on the hydrogen evolution were systematically investigated.The catalytic test demonstrated that 10 wt% Mo S2-Cd S show a high H2 evolution rate of 8.5 mmol g-1 h-1,which is 17 and 2.4 times higher than bare Cd S nanospheres and 1 wt% Pt-Cd S-PR,respectively.(3)The acrylamide was selected as a co-monomer of urea to construct functionalized g-C3N4-based catalysts by copolymerization,incorporating of C=C group into the g-C3N4 structure,resulting the extended delocalization of ? electrons,thus the range of light absorption was enlarged,resulting a better photocatalytic performance.The catalytic test showed that CN-AM-20 exhibited an excellent catalytic performance and cyclic stability.