Synthesis Of Graphene/Metal Composites/Pt For Formaldehyde Oxidation At Room Temperature

With the change of life and work style,people spend about 90%of their time indoors,so indoor air quality becomes particularly important.Formaldehyde is one of the main factors affecting indoor air quality.Long-term exposure to formaldehyde will cause great harm to people's health.At present,the common methods to remove formaldehyde include physical/chemical adsorption,plant purification,photocatalytic oxidation,plasma oxidation,and thermal catalytic oxidation.Among them,catalytic oxidation at room temperature is regarded as the most promising method,because it can degrade formaldehyde into carbon dioxide and water without any additional lighting,heating,and plasma devices.In this paper,two hierarchical graphene/metal composite materials were prepared,and platinum nanoparticles were loaded on their surfaces by impregnation-chemical reduction procedure.The obtained catalysts showed excellent catalytic degradation activity and stability at room temperature.The main contents are as follows:?1?Graphene oxide?GO?suspension was prepared by modified Hummers method,and then nickel-iron layered double hydroxide/reduced graphene oxide?NiFe-LDH/rGO?nanocomposite with hierarchical honeycomb-like structure was prepared by one-step hydrothermal method.Finally,Pt/NiFe-LDH/rGO catalyst was obtained by impregnation-sodium borohydride reduction method.The SEM and TEM images showed that uniform NiFe-LDH nanosheets are distributed vertically and evenly on the surface of rGO layers,thus enabling it to have abundant pore structure and larger specific surface area,which is conducive to the diffusion of gas-phase reaction media,the exposure of more surface reactive sites,and the dispersion of platinum nanoparticles.In addition,in situ diffuse reflectance infrared Fourier transform?DRIFT?spectroscopy showed that dioxymethylene and formate were the main reaction intermediates,and the possible catalytic reaction mechanism and process were deduced.Compared with the control samples,the catalyst Pt/NiFe-LDH/rGO exhibited greatly enhanced oxidation performance,suggesting that graphene composites have a certain application prospect in indoor formaldehyde purification.?2?Based on the above work,we also studied the formaldehyde oxidation activity of transition metal oxide/graphene oxide composites at room temperature.The support NiMn₂O₄/rGO and its corresponding supported noble metal catalyst were prepared by hydrothermal method and sodium borohydride reduction method.The results of electron microscopy show that the presence of rGO transforms the products from agglomerated microspheres into sandwich-like hierarchical structures,thus avoiding the agglomeration of NiMn₂O₄ nanosheets.Thus the catalyst has large specific surface area,which is beneficial to exposing more surface active sites,and also conducive to the dispersion of platinum nanoparticles.In addition,redox reaction can take place between GO and KMnO₄,which accelerates the conversion of MnO₄^–,and greatly improves the yield of the catalyst.XPS analysis shows that there is electron transfer between rGO,NiMn₂O₄ and Pt,indicating the existence of interface and synergy effect.To investigate the catalytic HCHO oxidation mechanism,in situ DRIFTS measurement was conducted,and dioxymethylene and formate were major reaction intermediates.Compared with Pt/NiMn₂O₄,the catalytic activity of Pt/NiMn₂O₄/rGO was significantly enhanced,and the formaldehyde conversion was still impressive after cyclic testing.Therefore,the introduction of graphene improves the structure and intrinsic activity of the materials,which provides a new insight into fabricating novel three-dimensional nanocomposite catalysts.