Design Of Noble Metal-TiO₂ Composite Plasmonic Photocatalysts For Ethylene Degradation

Volatile organic compounds(VOCs)are one of the main culprits of environmental pollution,which are ubiquitous in the environment and are the most studied air pollutants in recent years.The traditional VOCs treatment methods have defects such as the inability to recycle the medium,the pollutants cannot be completely mineralized into carbon dioxide and water,the high cost,and the low environmental friendliness,while the photocatalysis has the advantages of strong mineralization ability,low cost,and stable catalyst.It is considered as an ideal way to degrade VOCs.However,the high bond energy and low adsorption capacity of non-polar gaseous organic pollutants represented by ethylene pose great challenges to the design of photocatalytic degradation materials.Semiconductor photocatalytic materials represented by titanium dioxide are widely used in photocatalytic reactions due to their low price and excellent stability.However,TiO2 has defects such as wide band gap and weak absorption of visible light,resulting in low light utilization efficiency and fast recombination rate of photogenerated carriers,which seriously restricts its photocatalytic activity.In addition,the non-polar and high bond energy properties of ethylene require that photocatalytic ethylene degradation materials require stronger photocatalytic activity to polarize,adsorb and degrade mineralized ethylene into carbon dioxide and water,meeting economic and environmental needs.Noble metal materials,especially gold,silver,platinum and their composites,exhibit a unique surface plasmon resonance(SPR)effect,which can enhance the overall photocatalytic activity.Due to the scarcity and high cost of precious metals,all-metal surface plasmonic materials have strong photocatalytic properties,but they cannot be used as industrial catalysts due to cost constraints.Loading precious metals on semiconductor materials can,on the one hand,enhance the overall light absorption capacity and photo-generated carrier separation capacity of the catalyst through the surface plasmon resonance effect.overall adsorption capacity and reduce catalyst cost.Therefore,the preparation of noble metal-semiconductor composite plasmonic photocatalytic materials by loading a small number of noble metals on semiconductors represented by titanium dioxide has become an ideal solution for industrialized photocatalytic degradation of ethylene.In this paper,flower-shaped titania microspheres are used as carriers with large specific surface area,and single noble metal gold,silver,and platinum nanoparticles are supported,and the modification of the structure of composite surface plasmon materials by different noble metals is explored.The optimal ratio enhances the photocatalytic degradation performance of ethylene;further co-loading gold and platinum on the titania microsphere carrier,the synergistic effect of AuPt enhances the visible light absorption ability and accelerates interfacial charge separation acting,achieving efficient and nearly complete photocatalytic ethylene degradation.Mineralization;Ag/AgBr-TiO2 ternary composite material was constructed,which broadened the absorption range of the spectrum and realized the high activity,high mineralization ability and high stability of the ternary composite material for photocatalytic ethylene degradation.The details are as follows:In the first chapter,the definition of non-polar organic small molecules and the traditional treatment methods of volatile organic pollutants are discussed.and the mechanism of photocatalytic degradation,photocatalytic degradation materials and modification strategies are proposed.The definition of surface plasmon effect and the mechanism of enhanced photocatalysis are further expounded,and metalsemiconductor composite plasmonic photocatalytic materials are proposed.Finally,the content and research significance of this thesis are introduced.In the second chapter,single noble metal gold,silver and platinum nanoparticles were loaded on flower-shaped titania microspheres,and the loading number of noble metals was adjusted to obtain the optimal loading ratio of each noble metal.The morphology,microstructure,and light absorption ability of the composites were further characterized,indicating that gold,silver,and platinum have surface plasmon effects with different intensities,thereby improving the photocatalytic ethylene degradation performance of the composites.In the third chapter,AuPt-TiO2 composite photocatalytic material was prepared by co-loading gold and platinum on flower-shaped titania microspheres,and its morphology,microstructure and light absorption ability were characterized.It is shown that Pt-coated Au forms AuPt nanoparticles supported on TiO2,which enhances the alllight absorption ability and accelerates interfacial charge separation acting through synergistic effect,thereby improving the generation and separation ability of photogenerated carriers,making it exhibit 19.9.4.64 and 2.42 times the photocatalytic ethylene degradation rate and 96%photocatalytic ethylene mineralization rate of TiO2 MSs,Au-TiO2 and Pt-TiO2.In the fourth chapter,Ag/AgBr-TiO2 ternary composite photocatalytic materials were constructed.The flower-like titania microspheres acted as carriers to disperse and stabilize Ag/AgBr,broaden the spectral response range,and excite more photogenerated carriers.Efficient degradation and near-complete mineralization of ethylene was achieved.Finally,the research content of this paper is summarized,and the main innovations of this paper are discussed.Aiming at the shortcomings of this paper,a further research plan is proposed,and the future work is prospected.