Preparation And Photoelectrochemical Performance Of Nitrogen Doped Graphene-Based And Bismuth Functional Composites

Due to its diverse structure,excellent photoelectrochemical（PEC）activity,and high photoelectrocatalytic efficiency,bismuth materials have become a research hotspot in many fields.Recently,studies on the PEC properties of bismuth materials show that they also exist some limitations in practical applications,for example,the low separation efficiency of photogenerated electron and hole pairs.In this thesis,a series of nitrogen doped graphene-based and bismuth functional composites were prepared by rationally introducing nitrogen doped graphene-based materials with different dimensions,which effectively improved the separation efficiency of the photogenerated electron and hole pairs for bismuth materials,and explored the mechanism of enhanced PEC performance.At the same time,the prepared functional composites as photoactive materials were fabricated to a PEC sensing platform,realizing the PEC detection of the target.The details were as follows:1.Nitrogen doped graphene nanoribbons supported BiOBr nanosheets（NGNRs/BiOBr）functional composites were prepared by one-step hydrothermal method.The results of PEC performance demonstrated that NGNRs/BiOBr functional composites were significantly superior to BiOBr.And when the starting mass ratio of NGNRs to Bi（NO₃）₃·5H₂O was 5%,the photocurrent response of NGNRs/BiOBr functional composites was optimal,which was 5 times higher than that of BiOBr.This was ascribed that introduction of NGNRs improved the charge transfer rate,effectively suppressed the coincidence of photogenerated electrons and holes,and thus led to an enhanced photocurrent signal.A PEC sensor was fabricated using NGNRs/BiOBr functional composites as photoelectric materials for PEC detection of aflatoxin B₁ in real samples.2.Nitrogen doped graphene quantum dots anchored rodlike Bi₂S₃（NGQDs/Bi₂S₃）functional composites were prepared by solvothermal method.The results of PEC performance showed that NGQDs/Bi₂S₃ functional composites were significantly superior to Bi₂S₃.Theoretical calculation of the conduction band and valence band for Bi₂S₃ and NGQDs,electron spin resonance（ESR）radical-trapping experiments confirmed that the internal electron transfer of NGQDs/Bi₂S₃ was“Z-scheme”path,revealing that the reason for high separation efficiency of photogenerated electrons and holes of NGQDs/Bi₂S₃.Using NGQDs/Bi₂S₃ functional composites as the photoactive interface,sulfadimethoxine（SDM）aptamer was modified on the interface by covalent bonding.A highly sensitive and selective PEC aptamer sensor for SDM was fabricated,achieving PEC detection of SDM in real samples.3.A series of functional materials including BiOCl,BiVO₄,BiOCl/BiVO₄,NGQDs/BiOCl,NGQDs/BiVO₄,and NGQDs/BiOCl/BiVO₄ were successfully prepared by hydrothermal method.Mott-Schottky experiments confirmed that BiOCl is a p-type semiconductor,BiVO₄ is an n-type semiconductor,and NGQDs possess both p-type and n-type conductivities.NGQDs/BiOCl/BiVO₄ is a ternary heterojunction.The p-n diodes system caused an internal Z-scheme charge separation and transfer route in NGQDs,which facilitated efficient separation of photogenerated electron and hole pairs in NGQDs/BiOCl/BiVO₄.Comparing to a series of bismuth functional materials for PEC performance,NGQDs/BiOCl/BiVO₄ ternary heterojunctions had the optimal photocurrent response.At the same time,the results of UV-vis diffuse reflectance spectroscopy,steady-state photoluminescence（PL）spectra and time-resolved transient PL decay demonstrated that NGQDs/BiOCl/BiVO₄ possessed broaden the visible light absorption range,reduced the band gap energy,decreased the PL intensity,and increased the carrier lifetime.The PEC sensing platform was successfully fabricated using NGQDs/BiOCl/BiVO₄ ternary heterojunctions as the sensing interface,and PEC detection of dopamine was achieved.