the introduction of silver slightly decreases the CeO2 particle surface area.
indicating that silver nano particles formed on the surface with blocking pores of CeO2 nanospheres.
室内甲醛净化催化剂研究进展
642081701058 王俊杰
主要内容

研究背景
文献分析 前景展望


Introduction

随着经济的快速发展 ,人们的居住环境也不断改善 ，由于室内装 潢材料中有害物质对人体的影响不断加大，其中甲醛是室内空气 主要污染物之一 ，对其进行研究具有重要意义 。
当室内空气中含量为0.12毫克每立方米时就有异味和不适感;0.5 毫克每立方米可刺激眼睛引起流泪； 0.6毫克每立方米时引起咽 喉不适或疼痛；浓度再高可 引起恶心、呕吐、咳嗽、胸闷、气喘 甚至肺气肿；当空 气中达到30毫克每立方米时可当即导致死亡。
The preparation of the catalyst
制备四组催化剂备用： Ag/CeO2-N 纳米球颗粒 CeO2-N
Ag/CeO2-P CeO2-P 普通颗粒
The Ag contents on both Ag/CeO2–N and Ag/CeO2–P were approximately hod


控制室内温度 、湿度（甲醛的释放随着湿度的增大而增加，随温 度升高而增大 ） 物理吸附技术（各种活性炭 、多孔粘土矿石 、硅胶等 ） 催化技术（近几年研究比较多的纳米光催化技术） 空气负离子技术（具有明显的热电效应的稀有矿物石，在与空气 接触中，电离空气及空气中的水分，产生负 离子） 臭氧氧化法 光触媒（室内所有物体表面形成一层光触媒纳米透明薄膜） 生物技术（微生物以有机物为其生长的碳源和能源而将其氧化 、 降解 ）
Characterization of catalyst
Crystal and structural properties（TEM、BET 、XRD）
Both of CeO2 and Ag/CeO2 products are the nanosphere shapes with average sizes around 80–100 nm (Fig. 2a and b). Ag/CeO2-N nanospheres are comprised of many small particles with a crystallite size of 2–5 nm, and there are clear voids among the small particles.
common main peaks at 529.3 eV might be ascribed to lattice oxygen (Olat), and the peak at 531.3 eV could be attributed to surface chemisorbed oxygen (Osur).
The oxygen defect sites of the catalysts, which followed the sequence CeO2-N > Ag/CeO2-N>>Ag/CeO2-P > CeO2-P.
The abundant oxygen vacancies could adsorb and activate O2 for facilitating the catalytic oxidation Reaction.
The corresponding elemental maps of Ag/CeO2-N nanospheres show that both Ce and Ag are well distributed throughout the individual Ag/CeO2 nanosphere crystal (Fig. 2d).
at 38.2◦ and 44.4◦ are detected on Ag/CeO2-P catalysts, which could be attributed to the (1 1 1) and (2 0 0) Bragg’s reflections(布拉格反射) of the face-centered cubic (fcc 面心立方结构) structure of Ag. Note that, the diffraction peaks at 38.1◦ could be also the(2 0 0) Bragg’s reflections of bodycentered cubic (bcc体心立方结构) structure of Ag2O .Therefore, it is difficult to exclude the presence of Ag2O on the Ag/CeO2-P catalysts.
Reaction intermediated
The bands around 1580 cm−1, represented HCOO− generation, are formed after HCHO is introduced on the CeO2 and Ag/CeO2 catalysts.
The presence of silver nano particles promoted desorption of surface active oxygen on Ag/CeO2-N catalysts. Compared to other catalysts, Ag/CeO2-N catalysts would easily desorb surface active oxygen species and exhibit higher catalytic activity for formaldehyde oxidation.
前景与展望

在开发具备室温催化氧化性能的催化剂 过程中，通过对活性组分和制备工艺的 改进，在追求高催化活性的同时，降低 催化剂成本，简化制备工艺，获得高效 稳定和廉价易得的非贵金属基催化剂将 是今后的主要研究方向。
Therefore, we speculate that parts of the Ag nano particles are oxidized, and both metallic Ag and Ag2O are formed on Ag/CeO2-N catalyst surface.
Active surface oxygen
XPS
The Ag3d5/2 binding energy of Ag/CeO2-P catalysts is 368.3 eV, which could be attributed to the Ag 0 of the metal Ag. Meanwhile, the binding energy of Ag/CeO2-N catalysts slightly shifts to lower value of 368.0 eV indicating the formation of oxidation state of silver nano particles on the surface of Ag/CeO2-N catalysts. Since the binding energy for Ag+ of Ag2O is always around 367.6–367.8 eV
The much more surface chemisorbed oxygen might be beneficial to activate the HCHO molecules that facilitated the catalytic oxidation reaction
Raman spectra
Ag/CeO2 nanospheres: Efficient catalysts for formaldehyde oxidation
Applied Catalysis B: Environmental 148–149 (2014) 36–43
Many kinds of catalysts, including transition metal oxide（过渡金属氧化物） and precious metal catalysts, have been reported to be active for complete catalytic oxidation technology of formaldehyde elimination. For example, Transition metal oxide catalysts included MnO2 , Cr2O3 ,Co3O4 , and Co–Mn oxide . On the basis of present research, some of the catalysts based on precious metals could achieve complete catalytic oxidation of HCHO, such as Au/CeO2 ,Pt/TiO2 , Pt/MnOx-CeO2 .However, with the price of precious metals continuing to increase, it is still a challenge for developing low cost catalysts.