Design And Synthesis Of The Catalysts With Controllable TiO₂ Facets And Their Performances For The Photocatalytic Reduction Of CO₂

Carbon dioxide is one of the main contributors to greenhouse effect,the recycling of CO₂ has become an important topic in recent years.A growing interest in the semiconductor-based photocatalytic reduction of CO₂ with H₂O to renewable hydrocarbon fuels by solar energy has been evolved.It is the most important step for us to find suitable semiconductor material in photocatalytic study.The aim of this dissertation is to find a series of semiconductor catalytic materials with high catalytic activity,and study the mechanism of photocatalytic reduction of CO₂.The main research contents and conclusions were summarized as follows:Synthesis of TiO₂ with different micromorphology and their performances for the photocatalytic reduction of CO₂: We prepared three different kinds of TiO₂ crystals with special morpgology,and investigated their performances for photocatalytic reduction of CO₂.It was found that the optimal ratio of the exposed?101?and?001?facets on the enhancement of photocatalytic performance of TiO₂ is important.Controllable synthesis of anatase TiO₂?001?facets and their photocatalytic performance:It is widely believed that the ratio of exposed?001?facets depends on the concentration of fluorinion which could cause an exceptional stabilization of the?001?facets.Combining the DFT calculations and experiments,we found that HF molecule as the new controlling factor of exposed?001?facets is proposed and identified.The main reason to increase of the ratio of exposed?001?facets is that HF molecule can dramatically decrease the surface tension of?001?facets,but it has negligible influence for?101?facets.Two kinds of TiO₂ crystal with different optimal ratios of exposed?001?facets were synthesized and their photocatalytic performance were improved for photocatalytic CO₂ reduction and H₂O splitting reactions.Design and synthesis of TiO₂-loaded noble metal catalysts and their performances for the photocatalytic reduction of CO₂: A series of TiO₂-supported noble metal?Pt,Ru?nanoparticles are successfully synthesized.Compared their performances for photocatalytic reduction of CO₂,we found that although two kinds of noble metals can both enhance the photocatalytic activity,they have different impact on catalytic selectivity.By introduction of H₂ into the reaction system,we found that H₂ plays a key role in the production of CH₄ during photocatalytic reduction of CO₂.The yield of CH₄ production was increased significantly in the presence of H₂.The selectivity of CH₄ in photocatalytic reduction of CO₂ can be enhanced by supported noble metal on TiO₂ due to the improving ability of photocatalytic splitting of water.