Study On The Preparation And Performance Of Au And Au/g-C₃N₄/MMT Plasmon Resonance Photocatalysts

Due to the rapid development of modern manufacturing industry,serious pollution from industrial wastewater is also threatening the water ecological environment closely related to human beings.Especially for the past few years,the threat of dye wastewater pollution has increased dramatically.The use of general wastewater treatment methods may consume large amounts of energy and may induce secondary pollution in the treatment process.At present,photocatalytic technology,as an emerging new process for environmental pollution treatment,is favored by many researchers and scholars for its easy operation,low cost,high degradation efficiency,and economic environmental protection without secondary pollution.Meanwhile,in recent years,researchers have found that the local surface plasmon resonance effect（LSPR）of noble metal nanoparticles enables them to exhibit strong absorption of visible light,which significantly improves the utilization of sunlight.Therefore,based on plasmon resonance effect,two enhanced photocatalytic degradation schemes based on gold nanoparticles were proposed.1.AuNPs were produced by the thermal reduction method,and AuNPs were characterized by transmission electron microscopy（TEM）.The enzyme-like catalytic activity exhibited by gold nanoparticles in the reaction of oxidative degradation of rhodamine B（RhB）based on plasmon resonance effect enhancement catalytic H₂O₂was studied under visible light.The oxidative degradation of RhB by H₂O₂catalyzed by AuNPs was observed through a UV-Vis spectrophotometer,and the AuNPs mediated peroxidase-like reaction was evaluated through the construction of an enzyme-catalyzed kinetic model.The results showed that AuNPs had good peroxidase-like catalytic activity for the oxidative degradation of RhB by H₂O₂exposure to visible light.By analyzing the results of light wavelength and light intensity dependent reaction rate,free radical capture,and hole receptor incorporation experiments,it is found that AuNPs absorb photon energy and generate a large number of hot carriers through local surface plasmonic resonance（LSPR）effect under light irradiation,in which hot electrons are pumped into H₂O₂molecular orbitals according to energy matching After receiving hot electrons,H₂O₂produces a large number of hydroxyl radicals with strong oxidation ability,which acts on RhB and eventually oxidizes it.Moreover,the addition of ethanol can consume holes and improve the efficiency of hot electron injection,thus improving the catalytic efficiency.The results of the study provide an idea of using the enzyme-like activity of gold nanoparticles under plasmon resonance excitation to treat dye wastewater.2.In this study,Au/g-C₃N₄/MMT（AGM）ternary nanocomposite photocatalysts consisting of AuNPs,graphitic phase carbon nitride,and montmorillonite were designed and prepared for the first time.Using scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,Fourier infrared spectroscopy（FT-IR）,x-ray photoelectron spectroscopy（XPS）,ultraviolet-visible spectroscopy（UV-vis）,and photoluminescence spectroscopy（PL）,we have accurately characterized the form and structure of the photocatalysts.The synergistic degradation effect of AGM ternary nanocomposite photocatalysts was investigated in the photoreaction system under visible light conditions using acid orange 7（AO7）as the target dye.The experimental results of photocatalytic performance showed that both montmorillonite as a carrier and loaded nano-gold could significantly improve the degradation efficiency of g-C₃N₄in solution for AO7.Meanwhile,the ternary photocatalytic material showed the best degradation efficiency,which was 2.7 times greater than that of single g-C₃N₄under the best AuNP doping conditions.The study of the photocatalytic degradation reaction mechanism reveals that the enhanced photocatalytic activity of the AGM composites mainly comes from two aspects:firstly,it improves the photoavailability of the catalyst and increases the electron transfer rate through the plasmon resonance effect of gold nano;secondly,it reduces the composite rate of photogenerated carriers and provides more active sites by using montmorillonite as a carrier.The stability of the composites was verified by cycling experiments.The present work might provide some insights for exploring other efficient composite photocatalysts with excellent properties.