Fabrication Of Al₂O₃-supported Platinum Catalysts For Room-temperature Catalytic Formaldehyde Oxidation

The application of modern decoration and various construction materials seriously deteriorate the indoor air pollution.Volatile organic compounds?VOCs?are the main indoor air pollutants.As one of the most common VOCs,formaldehyde?HCHO?has been attracting worldwide attention because it may cause many human health problems.Therefore,to meet our needs for the indoor environment and human health,it is particularly significant to develop novel materials for effective indoor HCHO removal.However,most of commonly used HCHO purification methods,including plasma oxidation,physical and chemical adsorption,photocatalysis,thermal oxidation,plant purification,etc.,require expensive equipment,activation treatments,and large energy consumption,and therefore has not been widely utilized.Room-temperature catalytic oxidation,as a newly proposed method for HCHO oxidation,is considered one of the most promising indoor HCHO removal strategies in the future,due to its recyclability,convenience,remarkable catalytic ability and non-toxic products.In this work,flower-like spherical alumina and alumina molecular sieves were used as the support for platinum?Pt?nanoparticles deposition.The as-prepared Pt-supported catalysts were used for HCHO decomposition at room temperature,exhibiting impressive performance.The main contents include:?1?The flower-like Al₂O₃ microspheres with exposed{110}facets were synthesized by one-pot hydrothermal method,and corresponding Pt-supported catalyst?Pt/Al₂O₃?was tested for HCHO catalytic decomposition at room temperature.Owing to the unsaturated Al_3CC sites anchoring Pt nanoparticles?NPs?on Al₂O₃{110}facets,the Pt/Al₂O₃ catalyst possesses high Pt deposition.Therefore,the Pt/Al₂O₃catalyst exhibited higher HCHO decomposition activity than the commercial alumina and commercial titania counterparts.The excellent performance of the Pt/Al₂O₃ also results from its promoted adsorption/desorption of reactants/products,due to its large surface areas and hierarchical mesoporous structure.The DRIFTS results indicate that the interaction of HCHO with surface active oxygen caused the formation of dioxymethylene?DOM?and formate species,which can be further converted into carbonic acid and then CO₂ and H₂O at room temperature.This Pt-loaded alumina microsphere is an effective indoor HCHO purification material.?2?The recently prepared catalysts for HCHO catalytic oxidation at room temperature are mainly in a form of powder,but the powder samples are difficult to be recovered and processed in practical application,which hinders the promotion of these catalysts.Therefore,in our second work,Pt-deposited Al₂O₃ molecular sieves were prepared through an impregnation method.The as-prepared catalyst exhibited excellent catalytic activity and stability for HCHO decomposition.The enhanced catalytic performance towards HCHO oxidation is attributed to the large specific surface area,mesopore structure and well-dispersed Pt NPs achieved by the treatment of acid solution.Besides,the DRIFTS results indicate that DOM and formate species as intermediates are formed through the reaction between HCHO and surface hydroxyls.Then,the intermediates are further oxidized into CO₂ and H₂O by active oxygen atoms on Pt-Al₂O₃ catalysts at room temperature.Meanwhile,the consumed surface hydroxyls can be regenerated from the H₂O on catalyst surface,preventing the deactivation of catalysts.In this study,Pt-Al₂O₃ molecular sieve catalysts with efficient room-temperature HCHO decomposition overcome the disadvantages of powder-shaped catalysts in practical application owing to their good portability and recyclability,which is highly promising in actual application.