Research On The Performance And Mechanism Of Graphene-based Modified Photocatalytic Materials For Treating Industrial Pollutants

Air pollution seriously endangers the physical and mental health of human beings,and relying on traditional adsorption treatment is prone to the problems of adsorption saturation and low efficiency.TiO₂is one of the most widely studied catalysts,however,the low efficiency of single TiO₂and the tendency of recombination of photogenerated electron-hole pairs have restricted the further development of TiO₂.The research was carried out based on the problems that the morphological characteristics of relevant TiO₂catalysts in the treatment of industrial air pollution gases are too single,mainly in the form of particles,and the weak visible light catalytic activity of TiO₂.In this paper,prismatic block TiO₂-G covalent composites（PTG）with unique morphology were prepared by solvent thermal in situ growth method.Meanwhile,formaldehyde was used as a simulated industrial air pollutant treatment object to test the visible photocatalytic degradation effect of PTG on formaldehyde,so as to enrich the research of TiO₂-G-based composites in the treatment of industrial air pollutants.In addition,PTG was characterized by various characterization methods.It was found that the graphene sheets（Gs）and prismatic spheres of TiO₂（PT）in PTG were well bonded together,and PTG retained the crystal structure characteristics of Gs and PT;the overall morphology of PTG was a block structure,and the surface was covered with a large number of prismatic conical TiO₂spikes,and the spikes were covered with a large number of hemispherical bumps;the covalent bonds between Gs and PT in PTG were in the form of Ti-C and Ti-O-C binding;there are also a large number of pore structures between different PTG blocks,which are conducive to the smooth passage of formaldehyde gas;The visible light catalytic degradation of formaldehyde by PT and PTG was tested for its effectiveness,durability and multiple influencing factors,kinetic reaction fitting analysis,comparative analysis of commercially available products and structural stability characterization analysis.It was found that PT was able to degrade 61.6%of formaldehyde under 120 min visible light irradiation,and among PTG prepared with different Gs doping ratios,PTG with 2%Gs doping ratio had the best effect on formaldehyde degradation,and the final degradation rate of formaldehyde could reach80.1%.After five cycles of formaldehyde degradation tests,PTG still maintained the formaldehyde degradation rate of 77.6%,and the crystal structure of PTG before and after the cycle tests was analyzed by Raman characterization,and no obvious changes were found in the structure of PTG.In the test of various influencing factors,PTG with 30 mg usage had the best formaldehyde degradation effect;PTG at 40%RH ambient humidity showed the best formaldehyde degradation effect.The kinetic reaction fitting analysis of PT and PTG showed that the degradation process of formaldehyde by PT and PTG was in accordance with the first-order kinetic reaction process,and PTG had a better fitting effect with the fitting R²up to 0.987.Comparing with the commercial products,it was found that PTG had the advantage of using less amount to achieve similar formaldehyde removal effect of the commercial products.Finally,the EPR radical assay of PTG showed that PTG could produce strong and sustained hydroxyl radical and superoxide radical response signals under visible light irradiation.It further confirmed that PTG has good persistence of visible light response and speculated the possible formaldehyde catalytic degradation mechanism of PTG.