Research On Morphology-controlled Hierarchical Pt-supported Catalyst For Room-temperature Catalytic Decomposition Of Formaldehyde

Formaldehyde?HCHO?is a common air pollutant.HCHO can be completely decomposed into CO2 and H2O with the room-temperature catalytic oxidation technology with environmental-friendly,energy-saving,high efficiency and well recyclable characteristics.The catalysts supporting noble metal?Pt,Pd?usually possess excellent room-temperature catalytic performance,while the catalytic performance is closely related to the morphological structures and various physicochemical properties.In this thesis,two novel hierarchical composite catalysts which supporting Pt were synthesized.The two catalysts both exhibited enhanced catalytic activity for HCHO removal at room temperature.The main contents are as follows:?1?Two-dimensional ultrathin bismuth tungstate?Bi₂WO₆?nanosheet was hydrothermally synthesized with CTAB assistance.After loading with trace of Pt,the ultrathin Pt/Bi2WO6 catalyst exhibited significantly higher decomposition activity toward HCHO than that of corresponding bulk Pt/Bi2WO6.It is concluded that the excellent performance of the ultrathin Pt/Bi2WO6 catalyst is mainly attributed to the following aspects:First,the 2D ultrathin nanomaterial has larger specific surface area,and thus exposes more surface sites,which could increase the adsorbed concentration of gas reactants as well as improve the dispersivity of Pt NPs,affording more reaction centers;Second,the open hierarchical structure assembled with ultrathin nanosheets owns multiple channels and large pore volume,promoting the gases diffusion and transfer within the interior space,and accelerating the dynamic catalytic reaction;Third,H₂-TPR revealed the catalyst has highly active surface oxygen species.Finally,the reaction intermediates were detected by DRITFS,and the possible reaction mechanism was deduced.?2?As for the highly reactive manganese oxide?MnO₂?among the metal oxides,by morphology controlling and modification with template method,hierarchical core-shell MnO2 spheres and Pt/MnO2 composite catalyst were obtained.The novel Pt/MnO₂ catalyst showed enhanced performance for HCHO removal compared with the general Pt/MnO₂.The hierarchical hollow plate-spheres have abundant surface sites and multiple porous structure,which greatly promote the gases absorption,internal diffusion and homogeneous dispersion of Pt NPs.The chemisorption tests revealed the highly reactive and mobile surface oxygen species in the Pt/MnO₂,essentially enhancing its HCHO catalytic activity.Lastly,the reaction mechanism over the Pt/MnO₂ catalyst was also elucidated based on the detailed DRIFTS analysis.