Preparation Of Black Phosphorus Quantum Dots Composite Non-Metallic Based Photocatalyst And Photocatalytic CO₂ Reduction

Since 2015,black phosphorus（BP）has been widely studied in the field of photovoltaic devices and light-driven medical treatment by virtue of its unique quantum confinement effect,edge state effect and excellent photoelectric/photothermal effect after being stripped from bulk to prepare zero-dimensional quantum dots.However,the application of this material in photocatalytic CO₂ reduction is still in its infancy.Based on this,this paper constructs a variety of composite catalysts of black phosphorus quantum dots@non-metallic catalysts,and uses black phosphorus quantum dots（BPQDs）as a co-catalyst for photocatalytic CO₂ reduction.The main research contents and experimental conclusions are as follows:（1）One-dimensional（1D）carbon nitride nanotubes（CNNT）were synthesized by supramolecular assembly using traditional nonmetallic photocatalyst carbon nitride（CN）as matrix.Then,the binary hybrid photocatalyst was constructed by modifying black phosphorus quantum dots（0D-BPQDs）on 1D-CNNT.The reduction rate of CO₂ to CO reached 44.6μmol g-1 h-1,which is superior to the similar photocatalyst and carbon nitride nanotube matrix materials.Synchrotron radiation（XAFS）confirmed the structure of N-P electron transfer channels in BPQDs and CNNT.Time resolved fluorescence spectra（PL）show a faster rate of charge separation.in situ X-ray photoelectron spectroscopy（in situ XPS）confirmed the electron flow trend and active sites of the photocatalytic reactions.in addition,the presence of the main intermediate*COOH was verified by in situ FT-IR characterization.The construction of atomic N-P charge transfer channel effectively promotes the charge transfer and speeds up the catalytic rate.This work provides a new method for the design of BPQDs anchoring heterostructures in photocatalytic CO₂reduction.（2）BPQDs was successfully anchored to boron nitride nanofibers（BNNF）by B-P bond connection.The CO₂ reduction rate of BPQDs/BNNF photocatalyst is 12 times higher than that of BNNF matrix,and the CO precipitation rate is as high as 27.4 umol·g-1·h-1,which is better than the most common non-metallic photocatalyst.in situ X-ray photoelectron spectroscopy（in situ XPS）,isotope labeling and ultrafine spectroscopy（TA）show that the constructed atomic B-P charge transfer channel effectively improves the photoelectron transfer rate by nearly two orders of magnitude.in situ FT-IR spectroscopy determined the reaction path and photocatalytic mechanism.By using BN material with high specific surface area as matrix,a more compact B-P electron bridge is constructed,and the charge transfer rate is effectively improved,and the CO₂reduction activity is promoted.（3）0D/3D BPQDs/BNF multi-dimensional nonmetallic composite catalyst was prepared on the basis of flower-like boron,carbon and nitrogen（BNF）ternary material.Compared with BNF material,the photocatalytic performance of BPQDs/BNF has been improved nearly 3 times,reaching 29.4 umol·g-1·h-1.The band locations of the materials were calculated by UV-visible diffuse reflectance spectroscopy（DRS）and ultraviolet photoelectron spectroscopy（UPS）,and the influence of the change of band structure on the catalytic activity was analyzed.The separation and transport capacity of charge carriers in catalysts was studied by photoelectric chemical characterization.X-ray photoelectron spectroscopy（XPS）and in situ X-ray photoelectron spectroscopy（in situ XPS）tests confirmed the strong interaction between BPQDs and BNFS and the transport direction of electrons in the reaction.in situ FT-IR（in situ FT-IR）spectra were used to investigate the detailed changes of reaction intermediates.A number of electron transmission paths are constructed between the three-element boron,carbon and nitrogen nonmetallic material and black phosphorus,which strengthens the interaction force between BPQDs and the matrix BNF,and speeds up the photocatalytic reduction rate of CO₂.In summary,this paper prepared composite nonmetallic nanomaterials based on BPQDs and applied them in the study of photocatalytic CO₂ reduction.The precise chemical structure of hybrid materials was determined by relevant characterization,and the role of BPQDs as a cocatalyst in photoelectric conversion was explored by photoelectric test.The effect of BPQDs on the catalytic reaction kinetics was studied by femtosecond spectroscopy and in situ characterization,and the photocatalytic mechanism of BPQDs composite was deeply analyzed,which provided a theoretical basis for the subsequent material design and application.