单原子光催化剂的合成、表征及在环境与能源领域的应用

Single Atom Photocatalysts: Synthesis, Characterization and Applications in the Fields of Environment and Energy

绿色清洁的光催化技术可降解污染物、生产能源,是解决环境与能源问题的重要手段,但限于光催化材料成本及效率方面,难以实现大规模应用。近年来单原子光催化剂的诞生和发展为这一领域注入了新的活力,其合成、表征及应用的相关研究成为材料、化学、环境、能源等诸多领域的热点。与传统负载型光催化剂相比,单原子光催化剂表面的金属粒子的分散度达到原子尺寸,可呈现更高的催化活性和选择性,但对合成策略、表征技术和应用途径提出了更高的挑战:合成方面的主要障碍在于金属单原子的高表面能导致合成过程中的失稳团聚而丧失其单原子形态;传统的表征技术也缺乏对单原子形貌、结构及化学环境的解析能力;目前对单原子光催化剂的应用研究多为传统研究领域的延伸,未能充分利用单原子的功能特性。这些问题成为制约其发展的关键,也是该领域的研究热点。国内外学者在单原子光催化材料合成、表征和应用领域做出了巨大努力,并取得了丰硕成果:(1)合成方面,针对单原子表面能高、易团聚的问题,改进了液相合成法、原子层沉积法等传统合成策略,引进了新的高温裂解、火焰喷雾、静电自组装等技术;(2)表征方面,先进的原子尺度分析技术如球差校正高分辨透射电镜(HAADF-STEM)、X射线吸收精细结构谱(XAFs)等以及密度泛函理论(DFT)的发展则有助于深入理解孤立金属单原子形态及化学结构;(3)单原子光催化剂目前已被成功应用于光解水制氢、光催化CO2还原、环境污染物降解以及合成氨等领域,获得了长足的发展。上述成果推进了光催化材料及催化理论的研究向原子级别深入,使其进一步贴近实用化。本文综述了近年来单原子光催化剂的合成方法、表征技术以及在环境和能源领域的应用情况。同时,总结了目前单原子光催化材料研究中存在的问题。最后,展望了单原子光催化剂未来的发展趋势,以期为单原子光催化剂的理论研究及应用提供参考。

The green and clean photocatalytic process can degrade pollutants and produce energy,which is an important means to solve environmentand energy problems. However,it is difficult to realize large-scale application due to the cost and efficiency of photocatalytic materials. In recent years,the emergence and development of single atom photocatalyst have injected new vitality into this field,and the research on its synthesis,characte-rization and application has become a hotspot in many fields such as materials,chemistry,environment and energy.Compared with traditional supported catalyst,the metal particle dispersion on the surface of the single atom photocatalyst is atomic. Single atom photocatalyst can present a higher catalytic activity and selectivity,but there are still many challenges remaining in synthesis strategy,characterization and application way: main obstacle in the synthesis process lies in that high surface energy can lead to the instability of single atom. Traditional characterization techniques also lack the ability to analyze the morphology,structure and chemical environment of the single atom. At present,the research on the application of single atom photocatalyst is mostly an extension of the traditional research field. These problems become the key shackle of its development,but also the focus of the research in this field.Oversea and domestic researchers have made a great effort in the synthesis,characterization and application of single atom photocatalytic materials and achieved a lot of great results:( ⅰ) in terms of synthesis,to solve the reunite problem of single atom,researches have improved the traditional synthesis strategy,such as liquid-phase synthesis,atomic layer deposition etc. And advanced synthesis methods such as pyrolysis,flame spray pyrolysis and electrostatic self-assembly have been introduced.( ⅱ) In terms of characterization,the development of advanced atomic scale analysis techniques such as spherical aberration correction high resolution transmission electron microscopy( HAADF-STEM),X-ray absorption fine structure spectrum( XAFs),and density functional theory( DFT) can contribute to the in-depth understanding of the morphology and chemical structure of isolated metal atom.( ⅲ) Single atom photocatalyst has been successfully applied in the fields of photohydrolysis of water for hydrogen evolution,photocatalytic reduction of CO2,degradation of environmental pollutants and synthesis of ammonia,etc. The above achievements promote the research of photocatalytic materials and catalytic theory to the atomic level and make it more practical.In this paper,synthesis methods,characterization techniques and applications of single atom photocatalysts in the field of environment and energy are reviewed. At the same time,the existing problems in the research of single atom photocatalytic materials are summarized. At last,to provide reference for the theoretical research and application of single atom photocatalyst,the future development trend of single atom photocatalyst is prospected.