Study On The Influencing Factors Of Calcium Titanate For Hydrogen Production By Water Splitting Under Visible Light

In recent years,with the further research of perovskite compounds,the application properties of perovskite materials have been discovered gradually,such as outstanding catalysis,ferroelectric,high temperature superconducting and so on,which made perovskite received much research interest in the field of functional materials.Photocatalytic hydrogen production from water splitting,using perovskite as photocatalyst,is an ideal way to solve the energy crisis and environmental pollution problems.Hydrogen production using perovskite materials has made great progress at present,but many perovskite materials are only respond to ultraviolet light and have almost no activity under visible light irradiation,which restricts the development of the perovskite at a large extent.Moreover,The high efficiency recombination rate of photogenerated electrons and holes of perovskite decrease the photocatalytic hydrogen production rate under visible light irradiation.In this paper,visible light drived perovskite photocatalysts with high catalytic activity were synthesised,the photocatalytic hydrogen production conditions under visible light were investigated,the different sacrificial agents and loaded cocatalyst on photocatalytic activity were studied.The synthesised photocatalysts were characterized by XRD,BET,TG-DTA SEM,and UV-vis absorbance.(1)Catalyst Ca0.99La0.01TiO3 was synthesised by sol-gel technique.Catalyst Ca0.99La0.01TiO3-xNx was prepared by solid-state sintering method.From the UV-vis diffuse reflect spectra,we found that no significant absorption appeared in the visible wavelength range for Ca0.99La0.01TiO3,this catalyst cannot produce hydrogen under visible light whether it is HCHO or Na2SO3/Na2S as sacrificial agents.The absorption edge of catalyst Ca0.99La0.01TiO3-xNx is red-shifted and extends to the visible light range.Moreover,the catalyst Ca0.99La0.01TiO3-xNx can produce hydrogen under visible light when the sacrificial agent is HCHO,and cannot produce hydrogen when the sacrificial agent is Na2SO3/Na2S under visible light.(2)Loaded cocatalyst Pt promotes photocatalytic reaction and improves photocatalytic activity.When Ca0.99La0.01-TiO3-xNx is used as a catalyst,the optimum concentration of loaded cocatalyst Pt is 0.5%with adding HCHO as sacrificial agent,the hydrogen production is 40.037?mol/g in four hours.The optimum concentration of loaded cocatalyst Pt is 1%with adding Na2SO3/Na2S as sacrificial agent,the hydrogen production is 52.496?mol/g in four hours.Hydrogen production under visible light of photocatalyst Pt-Ca0.99La0.01TiO3-xNx adding four different kinds of sacrificial agents are compared,the results show hydrogen production that photocatalyst adding Na2SO3/Na2S shows the highest photocatalytic activity of hydrogen production from water,followed by HCHO and TEOA,while photocatalyst adding CH3OH as sacrificial agent does not produce hydrogen under visible light.(3)The minimum sintered temperature of Ca0.99La0.01TiO3/graphene was determined by TG-DTA.Combined with XRD and photocatalytic activity analysis,the optimum sintered temperature of the composite photocatalyst is 850?.The agglomeration of Ca0.99La0.01TiO3 particle happened on graphene seriously,the catalyst possess a BET surface area of 38.6m2/g.While the BET surface area of catalyst Ca0.99La0.01TiO3/graphene doped with nitrogen increased to 147.8m2/g,which can be ascribed to the microporous structure appeared.Moreover,nitrogen doping introduced more active site resulting in the increase of photocatalyti activity.Hydrogen production under visible light of catalysts Ca0.99La0.01TiO3-xNx?Ca0.99La0.01TiO3/graphene and Ca0.99La0.01TiO3-xNx/graphene adding HCHO as sacrificial agent were compared,the results show that photocatalyst Ca0.99La0.01TiO3-xNx/graphene possess the highest photocatalytic activity of hydrogen production from water,and the hydrogen production is 64.812?mol/g in four hours.