高活性氮化碳纳米片的制备策略

Strategies for the Fabrication of 2D Carbon Nitride Nanosheets

二维聚合物材料氮化碳纳米片因具有独特的电学特性、化学稳定性,在环境治理、能源转换领域有广阔的应用前景。开发绿色友好、经济高效的g-C_(3)N_(4)纳米片剥离策略和合成方法,是催化、能源、材料领域的热点问题。本文重点介绍了关于二维g-C_(3)N_(4)纳米片的剥离方法与制备策略的研究进展,同时对现有方法进行对比和分析,主要包括热氧化刻蚀、超声辅助剥离、化学法、机械法以及模板法等。文章的最后对g-C_(3)N_(4)纳米片的剥离制备所面临的问题和挑战,进行了讨论,并展望其未来发展方向。

Layered graphitic carbon nitride(g-C_(3)N_(4))is a typical polymeric semiconductor with an sp2π-conjugated system having great potential in energy conversion,environmental purification,materials science,etc.,owing to its unique physicochemical and electrical properties.However,bulk g-C_(3)N_(4) obtained by calcination suffers from a low specific surface area,rapid charge carrier recombination,and poor dispersion in aqueous solutions,which limit its practical applications.Controlling the size of g-C_(3)N_(4)(e.g.,preparing g-C_(3)N_(4) nanosheets)can effectively solve the above problems.Compared with the bulk material,g-C_(3)N_(4) nanosheets have a larger specific surface area,richer active sites,and a larger band gap due to the quantum confinement effect.As g-C_(3)N_(4) has a layered structure with strong in-plane C-N covalent bonds and weak van der Waals forces between the layers,g-C_(3)N_(4) nanosheets can be prepared by exfoliating bulk g-C_(3)N_(4).Alternatively,g-C_(3)N_(4) nanosheets can otherwise be obtained through the anisotropic assembly of organic precursors.Nevertheless,some of these methods have various limitations,such as high energy consumption,are time consuming,and have low yield.Accordingly,developing green and cost-effective exfoliation and preparation strategies for g-C_(3)N_(4) nanosheets is necessary.Herein,the research progress of the exfoliation and preparation strategies(including the thermal oxidation etching process,the ultrasound-assisted route,the chemical exfoliation,the mechanical method,and the template method)for two-dimensional C_(3)N_(4) nanosheets are introduced.Their features are systematically analyzed and the perspectives and challenges in the preparation of g-C_(3)N_(4) nanosheets are discussed.This study emphasizes the following:(1)The preparation method of g-C_(3)N_(4) nanosheets should be properly selected according to the practical application needs.Additionally,various strategies(such as chemical method and ultrasonic method)can be combined to exfoliate nanosheets from bulk g-C_(3)N_(4);(2)More reasonable nano-or even subnanostructured g-C_(3)N_(4) nanosheets should be continuously explored;(3)Novel modification strategies,such as defective engineering,heterojunction construction,and surface functional group regulation,should be introduced to improve the reactivity and selectivity of the g-C_(3)N_(4) nanosheets;(4)The application of in situ characterization techniques(such as in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS),electron spin resonance(ESR)spectroscopy,and Raman spectroscopy)should also be strengthened to monitor the detailed catalytic process and investigate the g-C_(3)N_(4) nanosheet structure-efficiency relationship.(5)To gain a deeper understanding of the relationship between the macroscopic properties and the microscopic structure,the combination of theoretical calculations and experimental results should be strengthened,which will be beneficial for exploiting high-quality g-C_(3)N_(4) nanosheets.