Assembly And Photocatalytic Hydrogen Production Over Graphitic Carbon Nitride/Organic Dye Composites

Due to the growing energy crisis and environmental pollution problems,renewable and clean energies are vital to be developed.Solar energy and hydrogen energy are recognized as two potential new energies.The conversion of solar energy into hydrogen energy through photocatalytic technology has attracted great attention from researchers.Among them,the design and assembly of efficient and stable catalysts are the focus of research.In this article,carbon nitride was used as the main substrate,and its assembly with conjugated organic compounds such as Eosin Y(EY),porphyrin,and Rhodamine B(RB)was adjusted through the metal ion/metal.Subsequently,a series of highly efficient photocatalysts for hydrogen production were achieved.Furthermore,the assembly mechanism,photocatalytic activity of hydrogen evolution,and photogenerated electron transfer mechanism were studied.The main contents are summarized as the followed:This work proposes a novel carbon nitride-based hybrid(g-C₃N₄/Cu/THPP)with small-sized Cu as the bridging linker for improving the photocatalytic activity of graphitic carbon nitride(g-C₃N₄)/tetrakis-(4-hydroxyphenyl)porphyrin(THPP).It was found that the special Cu linker had a great influence on the microstructure and photocatalytic H₂ production of the g-C₃N₄/THPP nanohybrid.The photocatalytic activity was enhanced by about 17.3times compared to that of pristine g-C₃N₄ and about 11.6 times higher than that of g-C₃N₄/THPP.Especially,it was enhanced by about 3.1 times than that of g-C₃N₄/Cu THPP(a comparative composite without the Cu bridge).Furthermore,the photocatalysis mechanism was investigated in detail.The results demonstrated that interfacial modification with the special Cu linker was key in improving the absorption,electron/hole separation and photocatalytic performance of the nanohybrid.This work provides a facile strategy for preparing highly efficient photocatalysts through interfacial modifications with special metals.A stable g-C₃N₄/cobalt ions/EY nanohybrid with improved photocatalytic performance by interfacial implantation of cobalt ions.The interaction mechanism among components was explored in detail.The nanohybrid with optimal embedding of 5.0 wt.%cobalt ions showed about 18 times higher activity for H₂ production than that of the g-C₃N₄,and also greater than the sum of g-C₃N₄/EY and g-C₃N₄/cobalt ions.It was denoted that there existed synergistic interaction between g-C₃N₄/cobalt ions and EY.Moreover,the obtained nanohybrid was more stable and active.The photocatalytic mechanism was further investigated by means of photoelectronic measurements,fluorescence spectra,and electron paramagnetic resonance spectra.It was found that,recombination of photogenerated charges was efficiently inhibited owing to strong interfacial interaction in the nanohybrid.It will offer a facile and low-cost way for fabricating other efficient heterogeneous photocatalyst by interfacial implantation of metal ions.An efficient and stable photocatalyst for hydrogen production was constructed by co-sensitization of EY and RB on the g-C₃N₄ sheets bonded with Cu ions.The spectral complementarity of EY and RB was used to greatly improve the visible absorption of g-C₃N₄.The interaction among components in the composite system was studied by detailed spectral analysis.It was found that the binding between the dye and g-C₃N₄ can be strengthened by the introduction of copper ions,and electron transfer can also be effectively improved.Furthermore,the photocatalytic hydrogen production over the composites was studied.The result showed that,when EY and RB with the appropriate ratio was introduced,the photocatalytic activity of hydrogen production and stability of the catalyst system are higher due to effective light absorption and the synergistic effect of EY and RB.In this thesis,a series of graphite-phase carbon nitride photocatalyst systems with novel structure,excellent photocatalytic performance have been constructed through non-covalent interactions.It provides new ideas for the design and synthesis of other photocatalysts for hydrogen production.