Au/3DOM Co3O4: highly active nanocatalysts for the oxidation of carbon monoxide and toluene

Abstract

Three-dimensionally ordered macroporous Co3O4 (3DOM Co3O4) and its supported gold (xAu/3DOM Co3O4, x = 1.1-8.4 wt%) nanocatalysts were prepared using the polymethyl methacrylate-templating and bubble-assisted polyvinyl alcohol-protected reduction methods, respectively. The 3DOM Co3O4 and xAu/3DOM Co3O4 samples exhibited a surface area of 22-27 m(2) g(-1). The Au nanoparticles with a size of 2.4-3.7 nm were uniformly deposited on the macropore walls of 3DOM Co3O4. There were good correlations of oxygen adspecies concentration and low-temperature reducibility with catalytic activity of the sample for CO and toluene oxidation. Among 3DOM Co3O4 and xAu/3DOM Co3O4, the 6.5Au/3DOM Co3O4 sample performed the best, giving a T90% (the temperature required for achieving a conversion of 90%) of -35 °C at a space velocity of 20 000 mL g(-1) h(-1) for CO oxidation and 256 °C at a space velocity of 40 000 mL g(-1) h(-1) for toluene oxidation. The effect of water vapor was more significant in toluene oxidation than in CO oxidation. The apparent activation energies (26 and 74 kJ mol(-1)) over 6.5Au/3DOM Co3O4 were lower than those (34 and 113 kJ mol(-1)) over 3DOM Co3O4 for CO and toluene oxidation, respectively. It is concluded that the higher oxygen adspecies concentration, better low-temperature reducibility, and strong interaction between Au and 3DOM Co3O4 were responsible for the excellent catalytic performance of 6.5Au/3DOM Co3O4.

The effects of Au species and surfactant on the catalytic reduction of 4-nitrophenol by Au@SiO2

“…The peaks at approximately 83.8 and 87.5 eV can be assigned to Au 0 , and other peaks can be assigned to Au n+ according to previously published reports. [32][33][34][35][36][37][38] The XPS results reveal that the relative intensity of Au n+ steadily declines when increasing the annealing temperature, which is consistent with that reported in the literature. [39][40][41] When the annealing temperatures are 500 and 700 C, PVP is nearly completely removed from the surfaces of the samples.…”

Three-dimensionally ordered macroporous spinel-type MCr2O4 (M = Co, Ni, Zn, Mn) catalysts with highly enhanced catalytic performance for soot combustion

“…Figure 3 displays that all the 3DOM catalysts exhibited the typical type II N 2 adsorption-desorption isotherms with H3 hysteresis loop in the relative pressure (P/P 0 ) range from 0.8 to 1.0 combined with a small H2 hysteresis loop in the range from 0.2 to 0.8. [31][32][33] Meanwhile, their corresponding pore size distribution curves demonstrated the wide pore size range from mesopore to macropore, which further confirmed the above conclusion. [31][32][33] Meanwhile, their corresponding pore size distribution curves demonstrated the wide pore size range from mesopore to macropore, which further confirmed the above conclusion.…”

“…30 During the high-temperature calcination, the PMMA microspheres acted as building blocks for the spinel-type oxide frameworks and leaded to relatively moderate shrinkage of the macropores. 30,31 The H3 hysteresis loop, which does not clearly demonstrate any adsorption plateau at the relative pressures close to unity, could be attributed to the existence of slitshaped pores in catalysts, indicative of a part of pore size extending into the macropore range. 30,31 The H3 hysteresis loop, which does not clearly demonstrate any adsorption plateau at the relative pressures close to unity, could be attributed to the existence of slitshaped pores in catalysts, indicative of a part of pore size extending into the macropore range.…”

Synthesis of three-dimensionally ordered macroporous LaFeO3 with enhanced methanol gas sensing properties

“…As a special nanoarchitecture, the 3DOM structure is a promising candidate for improving the gas sensing properties of materials. The 3DOM structure serves a large surface area owing to its porosity structure [21], which can improve gas sensitivity of material [22,23]. Besides, gas diffusing can beneficiate from the ordered macroporous structure, which can improve sensing property via decreasing response and recovery times [24].…”