Design Of New Carbon-supported Noble Metal Catalysts And Study On Catalytic Oxidation Of Formaldehyde

Formaldehyde is a kind of indoor pollution that cannot be ignored.It always threatens human health.If people are exposed to formaldehyde for a long time,it may cause various discomforts and even cause cancer.With the process of scientific and the innovation of experimental methods,various methods for eliminating formaldehyde have been perfected.Among them,catalytic oxidation has the advantages of wide application,low energy consumption,non-toxic products,and is one of the most promising ways.The research focus of this method is on the design of the catalyst.There are two difficulties and key points.One is to maintain stable and efficient catalytic performance at low temperature,and the other is to reduce the cost of raw materials.Compared with other catalysts,the catalysts with noble metals as the main active sites have significant advantages in low temperature activity.In recent years,the research on new carbon materials in traditional fields such as thermal catalysis and electrocatalysis has been increasing.Especially graphene and its derivatives have shined in the field of catalysis with their unique two-dimensional planar structure and flexible chemical properties.Hence,in this study,graphene oxide was used as one of the typical representatives of new carbon materials as support,and a series of catalysts were prepared through a series of modifications.The performance of its formaldehyde oxidation was investigated,and series research of in-depth materials and chemical reaction mechanism were carried out.In this paper,a supported catalyst was prepared using graphene oxide as a support and Pt as a typical noble metal active site.First,it was confirmed that the Pt-based catalyst prepared by reducing chloroplatinic acid with ascorbic acid as a reducing agent had the best formaldehyde catalytic activity.Then,graphene oxide was improved by nitrogen-doping and loading CeO₂ as a promoter.The results showed that with 0.8%mass fraction of CeO₂ as an auxiliary agent,the nitrogen-doped graphene oxide only needed to load 0.7%mass fraction of Pt to achieve 100%formaldehyde conversion at room temperature of 30℃.And excellent catalytic stability was exhibited in a long-term experiment of 48 hours.Through a series of characterization methods,it was proved that nitrogen-doping increased the specific surface area of graphene oxide,which was helpful for the anchoring and dispersion of Pt.The presence of Ce³⁺in the CeO₂ resulted in more reactive oxygen species.At the same time,the results of in situ DRIFTS indicated that the oxidation mechanism of HCHO was simplified due to the rich hydroxyl groups of graphene oxide.Finally,graphene oxide doped with nitrogen,phosphorus,sulfur,and fluorine were prepared,and then loaded with 1%Pt（mass fraction）.The results showed that the nitrogen-doped sample had the highest formaldehyde conversion rate at low temperature,reaching 81.7%at 30℃.A series of characterization methods showed that nitrogen-doping had the best effect on increasing the specific surface area of graphene oxide,and sulfur-doping had the best effect on increasing the pore volume.The average particle size of Pt nanoparticles in all hetero-atom doped samples was smaller than that in undoped samples,indicating that hetero-atom was conducive to the dispersion of Pt.And the average particle size of platinum nanoparticles on the surface of sulfur-doped samples was the smallest.The oxidation mechanism of formaldehyde was also simplified due to the plentiful hydroxyl groups of the support,and no CO generation was observed.