Oxygen Adspecies Concentration Research Articles

P123-PMMA Dual-Templating Generation and Unique Physicochemical Properties of Three-Dimensionally Ordered Macroporous Iron Oxides with Nanovoids in the Crystalline Walls

Three-dimensionally (3D) ordered macroporous (3DOM) iron oxides with nanovoids in the rhombohedrally crystallized macroporous walls were fabricated by adopting the dual-templating [Pluronic P123 and poly(methyl methacrylate) (PMMA) colloidal microspheres] strategy with ferric nitrate as the metal precursor in an ethanol or ethylene glycol and methanol mixed solution and after calcination at 550 °C. The possible formation mechanisms of such architectured materials were discussed. The physicochemical properties of the materials were characterized by means of techniques such as XRD, TGA/DSC, FT-IR, BET, HRSEM, HRTEM/SAED, UV-vis, XPS, and H(2)-TPR. The catalytic properties of the materials were also examined using toluene oxidation as a probe reaction. It is shown that 3DOM-structured α-Fe(2)O(3) without nanovoids in the macroporous walls was formed in the absence of P123 during the fabrication process, whereas the dual-templating strategy gave rise to α-Fe(2)O(3) materials that possessed high-quality 3DOM structures with the presence of nanovoids in the polycrystalline macropore walls and higher surface areas (32-46 m(2)/g). The surfactant P123 played a key role in the generation of nanovoids within the walls of the 3DOM-architectured iron oxides. There was the presence of multivalent iron ions and adsorbed oxygen species on the surface of each sample, with the trivalent iron ion and oxygen adspecies concentrations being different from sample to sample. The dual-templating fabricated iron oxide samples exhibited much better low-temperature reducibility than the bulk counterpart. The copresence of a 3DOM-structured skeleton and nanovoids in the macropore walls gave rise to a drop in the band-gap energy of iron oxide. The higher oxygen adspecies amounts, larger surface areas, better low-temperature reducibility, and unique nanovoid-containing 3DOM structures of the iron oxide materials accounted for their excellent catalytic performance in the oxidation of toluene.

Three-dimensionally ordered and wormhole-like mesoporous iron oxide catalysts highly active for the oxidation of acetone and methanol

Three-dimensionally (3D) ordered and wormhole-like mesoporous iron oxides (denoted as Fe-KIT6 and Fe-CA) were respectively prepared by adopting the 3D ordered mesoporous silica KIT-6-templating and modified citric acid-complexing strategies, and characterized by a number of analytical techniques. It is shown that the Fe-KIT6-400 and Fe-CA-400 catalysts derived after 400°C-calcination possessed high surface areas (113–165m2/g), high surface adsorbed oxygen concentrations, and good low-temperature reducibility, giving 90% conversion below 189 and 208°C for acetone and methanol oxidation at 20,000mL/(g h), respectively. It is believed that the good catalytic performance of Fe-CA-400 and Fe-KIT6-400 was related to factors such as higher surface area and oxygen adspecies concentration, better low-temperature reducibility, and 3D mesoporous architecture.

Three-dimensional ordered mesoporous cobalt oxides: Highly active catalysts for the oxidation of toluene and methanol

Three-dimensional (3D) ordered mesoporous cubic Co 3 O 4 (denoted as Co-KIT6 and Co-SBA16) were fabricated adopting the KIT-6- and SBA-16-templating strategies, respectively. It is shown that Co-KIT6 and Co-SBA16 possessed large surface areas (118–121 m 2 /g), high oxygen adspecies concentrations, and good low-temperature reducibility. Over Co-KIT6 at space velocity = 20,000 mL/(g h), 90% toluene and methanol conversions were achieved at 180 and 139 °C, respectively. The excellent catalytic performance of Co-KIT6 and Co-SBA16 was associated with their larger surface areas, higher oxygen adspecies concentrations, better low-temperature reducibility, and 3D ordered mesoporous structure. High-surface-area 3D ordered mesoporous Co 3 O 4 (denoted as Co-KIT6 and Co-SBA16) can be fabricated with the KIT-6 and SBA-16-templating strategies, respectively. The Co-KIT6 and Co-SBA16 catalysts possess large surface areas, high oxygen adspecies concentrations, good low-temperature reducibility, and 3D ordered mesoporous structures, which are responsible for their excellent performance for toluene and methanol oxidation. ► Vacuum treatment favors the formation of 3D ordered mesoporous structure. ► 3D ordered mesoporous structure possesses high surface area. ► 3D ordered mesoporous structure exhibits good low-temperature reducibility. ► Mesoporous structure, reducibility, and oxygen species determine catalytic activity.