| During the past decades,with the rapid growth of population and fast development of economy,energy shortage and environmental pollution are the two outstanding issues to be addressed in the world,which have been widely taken into consideration.Photocatalysis technology is regarded as one of the efficient strategy to resolve the two thorny problems.Photocatalysis technology can not only convert the inexhaustible solar energy into chemical energy,but also degrade the organic contaminants to harmless substances.Moreover,Photocatalytic technology has a series of advantages such as mild reaction conditions,high efficiency,environmental friendliness and low price.Graphitic carbon nitride（g-C3N4）is a new type of semiconductor material,which has a smaller band gap and higher stability than traditional semiconductors.Due to wide range of raw materials and facile preparation,g-C3N4 is viewed as the star photocatalyst in the field of photocatalysis.However,the g-C3N4often suffers from insufficient visible light response capability and high recombination probability of photogenerated carriers,which limits its practical application.Therefore,to meet the requirements of practical application,g-C3N4needs to be modified.This dissertation is devoted to exploring the modified g-C3N4materials,with the purpose of improving its photocatalytic activity.The main contents are as follows:1、g-C3N4was prepared by thermal polymerization using melamine as raw material.Further,the ternary photocatalysts were prepared by compositing the MnFe2O4 coated with C microspheres（Mn@C）with g-C3N4.The mass ratio of Mn@C and g-C3N4 was adjusted to find the optimal load.In the experiment of photocatalytic degradation of methyl orange（MO）under visible light irradiation,20%Mn@C/CN presented the best photocatalytic activity,and the degradation rate of10 mg/L MO solution reached 99.3%in 75 min.Under the same conditions,using pure g-C3N4 as the catalyst,the degradation rate is only 50.3%.The first-order kinetic constant of 20%Mn@C/CN is 0.0549 min-1,which is about 6.2 times higher than that of g-C3N4.Through the characterization of the photoelectric properties of the composite photocatalyst,the enhanced photocatalytic performance can be ascribed to the effective separation and transfer of photogenerated electrons and holes.2、A series of Fe3S4/g-C3N4 photocatalysts were prepared by using the thermal polymerization and hydrothermal method.The photocatalytic performance of the as-prepared photocatalysts were evaluated by degrading the MO under visible light.The influence of the mass ratios of Fe3S4 and g-C3N4 were explored.The results indicated that 30%Fe3S4/g-C3N4exhibited the best photocatalytic activity,and the degradation rate of 20 mg/L MO solution reaches 98.4%in 120 min.The first-order kinetic constant is about 7.05 times higher than that of g-C3N4.The photoelectric characterization proved that the improvement of its photocatalytic activity is benefited from the effective separation of photogenerated carriers.3、Using melamine and ammonium chloride as the raw materials,porous g-C3N4with a larger specific surface area was prepared by thermal polymerization.The FeOCl/g-C3N4composite photocatalysts were prepared by calcining the mixture of g-C3N4 and FeCl3·6H2O.The photocatalytic activity of FeOCl/g-C3N4 was evaluated by photocatalytic water splitting.The effect of mass ratio of g-C3N4 of iron salt was explored.The results indicated that when the mass ratio of FeCl3·6H2O to g-C3N4 is40%,the photocatalyst demonstrated the optimum photocatalytic perfromance.Under3 hours of irradiation,the hydrogen production amount reached 5427.5μmol g-1,and the hydrogen production rate was calculated as 1913.4μmol g-1 h-1 by fitting the data points.while the hydrogen production rate of bulk g-C3N4 was only 24.5μmol g-1h-1under the same conditions.The photoelectric test results indicated that FeOCl/g-C3N4photocatalysts have more outstanding ability of charges separation and transfer. |
