Complex Three-Dimensional Co3O4 Nano-Raspberry: Highly Stable and Active Low-temperature CO Oxidation Catalyst

Abstract

Highly stable and active low-temperature CO oxidation catalysts without noble metals are desirable to achieve a sustainable society. While zero-dimensional to three-dimensional Co3O4 nanoparticles show high catalytic activity, simple-structured nanocrystals easily self-aggregate and become sintered during catalytic reaction. Thus, complex three-dimensional nanostructures with high stability are of considerable interest. However, the controlled synthesis of complex nanoscale shapes remains a great challenge as no synthesis theory has been established. In this study, 100 nm raspberry-shaped nanoparticles composed of 7–8 nm Co3O4 nanoparticles were synthesized by hydrothermally treating cobalt glycolate solution with sodium sulfate. Surface single nanometer-scale structures with large surface areas of 89 m2·g−1 and abundant oxygen vacancies were produced. The sulfate ions functioned as bridging ligands to promote self-assembly and suppress particle growth. The Co3O4 nano-raspberry was highly stable under catalytic tests at 350 °C and achieved nearly 100% CO conversion at room temperature. The addition of bridging ligands is an effective method to control the formation of complex but ordered three-dimensional nanostructures that possessed extreme thermal and chemical stability and exhibited high performance.

Comparison of the Micromorphology and Ultrastructure of Pollen Grains of Selected Rubus idaeus L. Cultivars Grown in Commercial Plantation

“…Given the commercial production of its fruit, Rubus idaeus has considerable economic importance in Europe and Poland [ 22 , 23 , 24 , 25 , 26 , 27 ]. Raspberry fruit is intended either for direct consumption or for processing in many industries: food [ 20 , 28 , 29 , 30 , 31 ], pharmaceutical [ 20 , 28 , 32 , 33 ], cosmetic [ 28 , 30 , 33 , 34 , 35 , 36 ], and nanotechnological [ 37 , 38 , 39 , 40 ] industries. Raspberry shrubs are a source of medicinal and cosmetic raw materials, i.e., Rubi idaeus fructus [ 41 , 42 , 43 , 44 , 45 ] and Rubi idaeus folium [ 20 , 46 , 47 , 48 ].…”

Facile Fabrication of Macroscopic Self-Standing Ni or Co-doped MnO2 Architectures as Catalysts for Propane Oxidation

“…The role of ammonium sulfate included: (1) modification of the nanostructure unit; the nanowires with large length-to-diameter ratio were obtained with the addition of ammonium sulfate and this morphology was favourable for the assembly, and (2) assistance to assembly; the ammonium sulfate functioned as bridging ligands and promoted the assembling of MnO 2 nanowires. It has been proposed that sulfate ions have two coordination sites which can bond water molecules via hydrogen bonds forming a three-dimensional network, and simultaneously coordinate metal nanoparticles, thus promoting nanoparticles self-assembly [14][15][16]. Therefore, the solvent of water also participated in the building process of the macroscopic assembly.…”

Aggregate ceramic films produced at room temperature by press forming

“…Since the basic concept of the MF method is that small particles are densely arranged in the voids between the large particles, it is thought that the flowability of the particles is related to the densification. Nanoparticles easily aggregate; however, it is possible to control their aggregation by modifying their surface properties . By integrating such advanced powder synthesis techniques, we expect that MF films will be obtained at lower press pressures.…”