Design, Synthesis And Photocatalytic Properties Of Mixed Phase MgTi 2 O 5 /MgTiO 3 Microspheres

With the acceleration of the industrialization,the demand for energy in the society has been increasing,which leads to the extensive use of traditional fossil fuels.This phenomenon,however,has not only caused a series of environmental problems,but also seriously affected people's production and life.Therefore,there is an urgent need to develop the new environmentally friendly energy conversion technology and produce the clean energy efficiently to serve the human society.As a very feasible way to solve energy and environmental problems,semiconductor photocatalytic technology has drawn much attention from the public in recent years.In particular,the photocatalytic hydrogen production technology can not only use the solar energy effectively but also produce clean hydrogen with high calorific value.However,the efficiency of current photocatalytic hydrogen production is still very low due to the lack of suitable semiconductor photocatalyst materials,which makes it difficult to use the technology practically.The development of new and efficient semiconductor photocatalyst is the key to improve the efficiency of photocatalytic hydrogen production.The mixed-phase titanate semiconductor is featured by high stability,low electron-hole recombination rate and high performance and is expected to be used in a practical semiconductor catalyst system in the future.But a series of scientific problems have not yet been resolved.Against this background,to solve the problems of difficult control and synthesis,the lack of surface catalytic ability and the poor utilization rate of visible light of the mixed-phase magnesium titanate semiconductors,this paper introduces the special design of metal-organic coordination method to synthesize the mixed-phase MgTi2O5/MgTiO3 microspheres and further improve its surface catalytic capacity and visible light utilization by means such as surface composite MoS2 and N doped.Besides,the mechanism of photocatalytic technology is also studied in this paper which mainly contain three parts:1.Magnesium titanate crystal has excellent chemical stability and good semiconductor photoelectric properties,hence a good photocatalyst body.However,using the traditional synthetic method is difficult to achieve morphological control.The material size of the material is large and the charge recombination is serious,which limit the application of magnesium titanate crystal in the field of catalysis.In this paper,we use salicylic acid as the organic ligand,MgTi-organic precursor framework with uniform microsphere morphologyis synthesized by using metal-organic complexation method.And it is calcination in air to obtain the mixed-phase MgTi2Os/MgTiO3 microspheres keep the morphology of precursor.The detailed test shows that the sample has good UV photocatalytic hydrogen production performance and good chemical stability.The heterojunction structure can effectively improve the charge separation efficiency of photocatalyst.In addition,this method has good universality.It can be used for the synthesis of a variety of divalent metal titanate.2.Mixed-phase MgTi2O5/MgTiO3 microspheres has good semiconductor properties,but their surface catalytic ability is poor.Although the traditional precious metal loaded method can effectively improve its surface photocatalytic capacity,its cost is too high,which does not meet the requirements of economic development.Taking into account the commonality of photocatalysis and electrocatalysis,this part attempts to improve the surface catalytic ability of mixed-phase MgTi2O5/MgTiO3 microspheres with MoS2 as a co-catalyst for its good electrocatalytic hydrogen evolution activity and relative low cost.The experimental results show that we have successfully reached the expectation of the experimental design through this method.And a new idea for improving the photocatalytic performance of the semiconductor is provided.3.As a semiconductor material with wide band gap,although the mixed-phase MgTi2O5/MgTiO3 microspheres has a good absorption of the UV light,it can not respond to visible light.Besides,it is difficult to use the traditional method to effectively modify the ion dopant without causing serious damage to its structure because of its stable crystal structure.In this part,a two-step method is used to realize nitrogen doped and reduce the width of its semiconductor band gap.The result shows that the photocatalytic hydrogen production under visible light irradiation is successfully realized and the hydrogen production rate can be up to 12 mol/h·0.1g or more.