Preparation Of Titanium Dioxide-based Composites And Performance Of Photoelectrocatalysis Ammonia Synthesis

Industrial ammonia synthesis（NH₃）is a very important chemical production technology that has a crucial impact on global economic development.However,due to its high energy consumption and large CO₂ emissions,it has fallen far behind the concept of sustainable development.In order to solve the energy shortage problem,it is very relevant to develop a green and sustainable ammonia synthesis technology that can better bring long-term sustainable development to society.Photoelectrocatalytic technology has the advantages of both photocatalysis and electrocatalysis and is therefore highly valued in a wide range of industries.The main work in this paper is an in-depth discussion of the synthesis of ammonia by reaction of nitrogen with water at ambient temperature and pressure,and the comprehensive development of highly efficient photocatalysts.The research is carried out with titanium dioxide（TiO₂）,which is one of the ideal photocatalysts due to its stable nature and tunable preparation process.However,TiO₂ has poor light trapping ability and photogenerated electron-hole complexation,which limit its application in photocatalytic ammonia synthesis.A series of studies on the performance of photocatalytic ammonia synthesis were carried out by preparing TiO₂ with different morphologies by hydrothermal synthesis,modifying it with co-catalysts and using UV spectrophotometer for quantitative ammonia detection,and evaluating the ammonia synthesis effect of the catalysts in terms of ammonia generation rate and Faraday efficiency.The aim was to solve the problems of low ammonia yield at room temperature and pressure and the inability of TiO₂ to use visible light effectively.The main studies and results are as follows:（1）TiO₂ nanosheets were prepared by solvothermal method,and Cu-Ag bimetals were synthesized on TiO₂ nanosheets by photo-induced deposition method and used for photoelectrocatalytic nitrogen reduction to ammonia reaction.Different ratios of Cu-Ag bimetals were prepared by adjusting the Cu and Ag dosages and screening the most suitable catalysts for nitrogen reduction ratios.The optimum reaction voltage was screened by testing the activity of different voltages.The experimental results showed that the ammonia yield of Cu-Ag/TiO₂ was 29.82μg·h^-1·mg_cat^-1 at-0.4 V（vs RHE）,which was 6.08 times higher than the ammonia generation rate of TiO₂,and the Faraday efficiency was 31.6%.It was also confirmed that the bimetallic catalytic activity was superior to that of a single metal,which was attributed to the fact that bimetallic metals generally have different interfacial properties from those of single metal surfaces as well as the mutual influence of the electronic structures of the two metals,which facilitates the activation of nitrogen adsorption on the catalyst surface.（2）TiO₂ nanobelts were prepared by one-step hydrothermal and calcination,and Ag/MoS₂/TiO_2-x ternary heterojunctions were synthesized by photoinduced deposition and in situ solid-state reduction for photoelectrocatalytic reduction of nitrogen to ammonia reaction.The use of narrow band gaps and black MoS₂ matched TiO₂ can enhance light capture.The ability to enhance the absorption of visible light by TiO₂semiconductors through local surface plasmon resonance and MoS₂ nanomaterials has important application potential.The experimental results show that the ammonia production rate of Ag/MoS₂/TiO_2-x reaches 39.44μg·h^-1·mg_cat^-1 at-0.4 V（vs RHE）,which is 7.14 times higher than that of TiO₂ with a Faraday efficiency of 42.66%.the Ag/MoS₂/TiO_2-x ternary heterojunction has higher ammonia production rate and photoelectrocatalytic activity.（3）Preparation of TiO₂ nanorad arrays by hydrothermal method for photoelectrocatalytic reduction of nitrogen to ammonia reaction using narrow band gap semiconductor MoSe₂ matched with TiO₂.Different ratios of MoSe₂/TiO₂ were prepared by adjusting the amount of MoSe₂ to select the best ratio of catalyst.It was shown that the yield was 37.14μg·h^-1·mg_cat^-1 at-0.2 V（vs RHE）voltage,which was 5.8 times higher than the ammonia generation rate of TiO₂ with a Faraday efficiency of 32.5%.the loading of MoSe₂ increased the electrical conductivity of the material,giving the catalyst a more negative current,leading to an increased yield of ammonia synthesis,giving it an efficient charge separation that It is favorable to accelerate the carrier migration and separation,while also promoting N₂ adsorption and reducing the reaction activation energy to increase the rate of ammonia production.