| In recent years,volatile organic compounds(VOCs)have caused serious air pollution,which made negative impact on human health economic development.Therefore,developing new technology for VOCs elimination is urgently needed.In this work,a series of manganese oxide(MnO_x)-based composite materials were constructed based on the catalytic reaction mechanism of photothermal materials for photothermocatalytic purification of formaldehyde.The photothermal synergistic catalytic performance of catalyst was detailedly studied.By studying the effect of light irradiation on the surface temperature of the catalyst,the relationship between wavelength range and photothermocatalytic performance that connected with reactive oxygen species(ROS)were clarified.The possible synergistic catalytic mechanism was also proposed.The main achievements are showed as follows:1.Using hydrothermal method to synthesize MnO_xnanosheets on graphene oxide(GO)nanosheets.The photothermal effect of GO converts solar energy into heat energy,which thus drives MnO_x to degrade formaldehyde at room temperature.Comparing with the GO,GO/MnO_xmixed mechanically,the hydrothermally synthesized GO-MnO_x exhibited significantly excellent performance for HCHO removal under the xenon lamp illumination.The HCHO concentration was rapidly decreased from ca.160 ppm to ca.10 ppm in 20 min.Experimental results using different illumination conditions indicated that the photothermal conversion was mainly from near infrared radiation(NIR).The Mars-van Krevelen mechanism was employed to explain the catalytic process of HCHO removal,where the adsorbed oxygen molecule and lattice oxygen atom were simultaneously activated under irradiation.2.Herein,a sponge based MS/PDA/MnO_x catalyst with plentiful 3D porosities was constructed by a two-step method.The dual-functional PDA layer not only promoted the MnO_xloading(25 wt%MnO_xin the composite),but also acted as a photothermal converter to absorb photo-irradiation that heating MnO_x catalyst(ca.80 ~oC after 10 min irradiation).Moreover,the3D network structure favored the mass transfer and effectively reduced the catalyst agglomeration to expose more active sites.As a result,the obtained MS/PDA/MnO_xphotothermocatalyst showed excellent conversion of HCHO within concentration at 40 to 320ppm under xenon light irradiation.This process followed a pseudo-second-order model,and the reaction rate of the MS/PDA/MnO_xwas 4.82 times comparing with that of MS/MnO_x.Finally,a possible photothermocatalysis mechanism was proposed based on the intermediate examination via the in-situ DRIFTS investigation.3.A ternary freestanding composite film catalyst that was prepared through a facile filtration method using two-dimensional GO,MnO_x and graphitic carbon nitride(CN)nanosheets as building blocks.The superior photothermal effect of GO rapidly enhanced the surface temperature to ca.85 ~oC,and then initiated the MnO_x thermocatalysis.Furthermore,the increased temperature also promoted the charge diffusion and surface reaction process of CN photocatalyst.Impressively,with the synergetic photothermocatalysis and photocatalysis,this composite film catalyst exhibited improved performance for catalytic oxidation of gaseous formaldehyde under xenon light irradiation.In addition,cycling experiments demonstrated that this film catalyst possessed excellent durability. |
