The Study Of Electronic State Regulation And Light-Driven Chemical Transformations Performance For Two-dimensional Solid Materials

The problems of resource depletion and environmental pollution have seriously jeopardized the sustainable development of mankind,and strategic initiatives such as energy-saving and emission reduction are of great significance.Inspired by nature,solar-driven conversion technology is an application that is undoubtedly an excellent solution.However,problems such as low photogenerated carrier separation efficiency and slow surface dynamics severely limit the efficiency of solar-driven conversion.Precise synthesis to prepare high-performance materials for light-driven conversion is the current research priority.This requires the use of precise synthesis combined with the design of tuning the surface electronic structure of the materials from the atomic scale,starting from the constraints of new energy conversion storage efficiency.This thesis work focuses on two-dimensional solid materials,optimizing the experimental scheme to regulate their electronic states,tracing their electronic arrangements,revealing the laws of multi-degree-of-freedom coupling of material charges,lattices,orbitals,and spins on the solar-driven conversion process,and exploring the conformational relationship between microstructure and properties of two-dimensional solid materials to achieve the optimal solar-driven conversion performance,thus opens a new path for the development of solar-driven conversion materials that provide a new directed chemical synthesis for designing high conversion rates.The research work of this papper mainly include the following areas:1.Multi-interface engineering constructs titanium dioxide/titanium carbide MXene/carbon nitride composites to enhance charge separation for efficient photocatalytic hydrogen precipitation:To systematically investigate the problem of potential energy conversion mechanisms between charge separation and transfer and photosynthetic systems,inspired by nature,we propose a multi-interface engineering strategy to construct a strongly coupled interaction transport network for stable and efficient photocatalytic hydrogen production.A multivariate all-solid-state Z-scheme structure with tight electronic interactions is formed through Tiorbital modulation and stacking hybridization between complex-phase structures.The electron-coupled structure ensures efficient carrier orientation separation and transfer,resulting in a significant 7.2 times increase in charge separation efficiency.In addition,the obtained materials have highly stable photocatalytic hydrogen precipitation performance up to15.29 mmol h^-1 g^-1,which is 18.8 times higher than that of pristine carbon nitride and exceeds most of the photocatalysts that have been reported so far.The work lays a good foundation for the design strategy high-speed charge transfer in the future.2.W₁₈O₄₉/TiO₂ nanoreactor construction and photocatalytic nitrogen reduction for ammonia synthesis:One-dimensional W₁₈O₄₉ were grown in situ on bronze-type TiO₂ two-dimensional nanosheets by an in situ hydrothermal synthesis method to construct a structure with a unique electronic structure.The Ti-O-W bonded electron transport channels were formed at the interface to precisely and efficiently control the charge flow,which led to the construction of an efficient solar-driven ammonia synthesis system for nitrogen immobilization.In conjunction with the in-situ realizations,we have performed in situ tracking of intermediates in the synthesis of ammonia and observed that the ratio of the three oxidation state valence states of W changes significantly during the light-driven conversion,and the surface electron enrichment of the active site W changes with the state,thus facilitating the synthesis of ammonia.This work elucidates that the structure plays an electron transport role in the solar-driven ammonia synthesis conversion from a chemical bonding perspective,and provides a new way to precisely design nanoreactor composite construction systems oriented to efficient photo-driven chemical ammonia synthesis.3.Triple-vacancy associate defect BiOBr boosting the photocatalytic synthesis of ammonia:Through the simple plasma method,we have designed BiOBr nanosheets with special electronic state structures,which are precisely identified by positron annihilation spectroscopy as well as spherical difference electron microscopy,and have a triple-vacancy conjugate defect structure.The introduction of the V_Bi^＇＇＇ V_Br^·V_Bi^＇＇＇ defect associate structure greatly reduces the exciton binding energy inside the material,providing more photogenerated electron activation to convert nitrogen molecules.Combined with theoretical simulations,the formation of the triple-vacancy defect-conjugate defect structure greatly reduces the energy barrier required for the reaction,which can greatly facilitate the reaction and finally achieve the ammonia synthesis efficiency of 460.04μmol g^-1 h^-1 under mild conditions.This work not only facilitates the further study of defect structures but also promotes the understanding and development of the conformational relationship between defect structures and ammonia synthesis performance.