Anatase-rutile Mixed Phase TiO₂ Photocatalytic Reforming Of Biomass For Hydrogen Production

Biomass energy has always been one of the important energy sources for human survival.Under the background of energy crisis in the world today,the development and utilization of biomass resources are paid more and more attention.Using photocatalyst to reforming biomass through photocatalytic reaction to obtain hydrogen energy is a biomass utilization method that attracts much attention,TiO₂ is a photocatalyst with excellent properties,which is widely used in the field of reforming biomass to produce hydrogen.In order to improve the hydrogen production activity of TiO₂,a lot of researches have been carried out.Anatase and rutile are two different crystal types of TiO₂ and are widely used in the study of various photocatalytic reactions.In most cases,the photocatalytic activity of anatase is higher than rutile,but for some special reactions?such as photocatalytic water oxidation?,rutile shows higher activity.More interesting is the phenomenon that the mixed-phase of anatase and rutile TiO₂ photocatalysts show higher photocatalytic activities than either pure anatase or pure rutile,which is called the synergetic effect between anatase and rutile.However,there is no consensus on the question of whether this synergy is real or not.This work focuses on checking the synergetic effect.Several series of anatase-rutile mixed-phase TiO₂ photocatalysts were prepared by calcining physical mixtures of amorphous TiO₂ and rutile at different temperatures.TEM,SEM,XRD and UV-Vis DRS were used to characterize the morphology,crystal phase and light absorption properties of these photocatalysts.The activities of these photocatalysts were evaluated with photocatalytic reforming of methanol for H2 production and photocatalytic degradation of methylene blue by using a mercury lamp,a xenon lamp or a mercury lamp filtered by a NaNO₃ solution as the irradiation sources.The results show that for all series of anatase-rutile mix-phase TiO₂ photocatalysts,the activities for both the photocatalytic methanol reforming and the photocatalytic degradation of methylene blue show the same trend,irrespective of the different light sources used in the activity evaluation:anatase has much higher activity than rutile,and the photocatalytic activities of the mixed-phase photocatalysts increase with the increasing of the anatase content.These results indicate that the synergy between anatase and rutile does not exist at all in these common TiO₂ photocatalytic systems.