| Direct Methanol fuel cell (DMFC) have drawn more and more attention due to their potential applications in portable electronic devices and electric vehicles. Compared with gas fuel, methanol is easier to transport and store, has higher energy conversion rate, and produces environmentally friendlier reaction products. The main limitations of DMFC anode are the high-price, the low activity and poor durability of Pt-based catalysts. This article revolves around the comprehensive utilization of CeO2. The synthesis, characterization of CeO2 and CeO2 composite oxides were researched. Then, they were applied to the anode catalyst of DMFC. We obtained the catalyst with better catalytic properties.First, we discuss the conditions on the synthesis of CeO2, CeO2 composite oxide, mesoporous carbon materials and its application in Pt/CMK-3 catalyst. SBA-15 and CMK-3 were synthesized with orderly two-dimensional six-party structure and large specific surface. Results show that the samples present the terbium oxide cubic crystal structure when the Ce/Zr and Tb/Zr≥0.6. The surface morphology of samples was irregular spherical nanoparticles with 5 nm of the particle size. The pores of the product were mainly concentrated in about 7.2 nm. The effect of CeC2 on the Pt/CMK-3 catalyst was researched. Found that the dispersion of the Pt on the supports was improved with CeO2. CeO2 can improve the activity of the catalyst significantly towards the methanol electrooxidation. The catalytic activity and stability were improved with the increase of CeO2 content, then they were reduced. Also we compared the effect of CeO2, Pr6O11, Tb4O7 on the properties of Pt/CMK-3. Similarly, we found that Pt-CeO2/CMK-3 catalyst has the highest electrocatalytic properties.In order to make fully play of the role of the CeO2 catalyst, we studied the effect of the different morphology CeO2 on the Pt/C catalyst. The different morphology CeO2 was synthesized successfully by hydrothermal method. Water temperature is a most important factors in all condition for CeO2 specific surface area. The best condition of preparation of flower CeO2 are calcinations temperature of 400℃, hydrothermal reaction temperature of 180℃, and hydrothermal reaction tmie of 48 h. Most of the Pt particles were distributed homogeneous and close on the flower-spherical CeO2.The distribution of Pt on Pt-9#CeO2/G catalyst can give full play of CeO2 synergistic catalytic effect. Compared with the Pt/G, the electron binding energy of Pt (0) in Pt-9#CeO2/G moved 0.6 eV. The strong interaction between flower-spherical CeO2 and Pt broke the electronic state ofa-πbetween CO and Pt break, thus the catalytic activity of Pt-9#CeO2/G was enhanced. The electrochemical active area (ECSA) of Pt-9#CeO2/G was 90.90 m2/g, which was 5.9 times of Pt/G catalyst and 2.4 times of Pt-1#CeO2/G catalyst.To implore a better carbon material for Pt-CeO2/C, the author prepared three kinds of Pt-CeO2/C(C is Graphene, mesoporous carbon, activated carbon respectively) catalysts, and investigated the structure and performance properties of them. It’s found that four elements in each of these three catalysts were evenly distributed. Compared Pt-CeO2/G and Pt-CeO2/CMK-3 with Pt-CeO2/XC-72, because graphene and mesoporous carbon have strong electronic interactions with Pt, the binding energy of Pt (0) in both Pt-CeO2/G and Pt-CeO2/CMK-3 shifted negatively in a certain degree, which accelerated-COads off from Pt and released the Pt activity. Furthermore, since the graphene surface contains more oxygen-containing functional groups as hydroxyl, carbonyl and carboxyl. it promotes the intermediate-COads to take off to enhance catalytic performance. The above factors result a fact that the ECSA value of Pt-CeO2/G catalyst reached as high as 111.25 m2/g, which is 2 times of Pt-CeO2/CMK-3 and 7.4 times of Pt-CeO2/XC-72.In order to modify metal Pt, PtNi(Cu)-CeO2/C catalysts with Cu or Ni as transition metal to modify active component Pt were prepared and studied respectively. It turned out that both Ni and Cu can apparently promote the catalytic performance of PtNi(Cu)-CeO2/C catalysts. In Pt-Ni/CeO2/G, Ni atoms went into the face-centered cubic lattice of Pt, and then Pt-Ni alloy was formed. Besides, in the graphene layer of Pt-Ni/CeO2/G catalyst, the author found a large amount of globular CeO2, on which Pt nanoparticles closely distributed. Further, when doped with 50% Ni (mole the ratio of Pt with Ni is 1:1), Pt-Ni/CeO2/G catalyst owned the best electric catalytic performance, and its CO adsorption test showed the lowest starting-off potential.Aiming to increase the formation capacity of reactive oxygen species in CeO2 surface to improve the performance of Pt/C catalyst, this study probed the influence of CeO2-ZrO2 composite oxides on Pt/C catalyst. In this study, the CeO2-ZrO2 formed into solid solution, and the element distribution of Pt are mainly found in CeO2-ZrO2 parts, except a small amount of it were combined with carbon. In these catalysts, CeO2-ZrO2 joined with Pt, and there are synergies between them. The addition of ZrO2 made CeO2 lattice distorted, as well as increased the mobility of oxygen vacancy and oxygen, thus the catalytic performance of Pt-MOX/C (M = Ce, Zr) catalyst towered over that of Pt-CeO2/ C. While the ratio of the amount of substance of cerium zirconium is 2:1, the sample showed the best catalytic performance. Under controlled conditions, the author successfully prepared needle flake CeO2-ZrO2 composite oxide synthesis and granulate one. Further, we found that 1), it is difficult to adsorb Pt particles on the surface of the needle flake CeO2-ZrO2, which led to weak catalytic effect; 2), conversely, Nano granulate CeO2-ZrO2 assumed better catalytic effect because of its large surface and adsorbing characteristics of Pt. |
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