Mesostructured Manganese Oxide/Gold Nanoparticle Composites for Extensive Air Purification

Abstract

Strong public concern and increasingly strict legislations [1] have made it highly imperative to devise versatile materials that can efficiently eliminate a wide range of organic pollutants from indoor and outdoor emissions. These pollutants contribute to photochemical smog and ground-level ozone and have raised severe concern owing to probable short-and long-term adverse health effects.[2] Most airpurification systems are based on photocatalysts, adsorbents such as activated carbon, or ozone-promoted oxidation. [3] However, all the currently used materials have limited efficiency in removing several volatile organic compounds (VOCs) under ambient conditions. Herein, we report a novel mesoporous manganese oxide/nanogold catalyst for efficient elimination of VOCs. To the best of our knowledge, g-MnO 2 materials reported to date have surface areas of no higher than 130 m 2 g À1 . [4] In the present study, mesoporous g-MnO 2 with a very high surface area (> 300 m 2 g À1 ) was obtained for the first time through a surfactant-assisted wet-chemistry route. Au nanoparticles were deposited on this oxide by a vacuum ultraviolet radiation (VUV)-assisted laser ablation (VALA) method to induce lattice defects [5,6] and strong metal-support interactions.[7] The material reveals an exceptionally good ability to remove VOCs (as well as NO x and SO 2 ) at ambient temperature, and this efficiency increases with increasing temperature. The high activity of these materials could be correlated to their redox properties and to the facile formation of radical species on their surface.We recently reported that high-surface-area mesoporous metal oxide materials are capable of eliminating VOCs at ambient temperature. [8][9][10][11][12] With these promising results in hand, we investigated a range of metal oxides and noblemetal catalysts and found that mesoporous g-MnO 2 with a very high surface area and modified with gold nanoparticles can efficiently eliminate a wide range of VOCs under ambient dark conditions. We chose three different classes of VOCs, namely acetaldehyde, toluene, and n-hexane, which are major components of indoor as well as outdoor organic pollutants, to demonstrate the efficacy of our mesoporous g-MnO 2 /nanogold catalysts.The mesoporous g-MnO 2 material rapidly eliminated acetaldehyde, with complete removal achieved within 1 h at room temperature ( Figure 1 b; see also Figure S1 in the Supporting Information) and with 18 % CO 2 formation after 24 h reaction (Figure 1 a). The formation of CO 2 increased rapidly with a slight increase in the temperature and reached 94 % at 60 8C (Figure 1 a). This result indicates that the acetaldehyde is rapidly adsorbed onto the mesoporous gMnO 2 and gradually decomposes on its surface. The efficiency of acetaldehyde removal is about 2-3-times better than those of conventional materials used to remove VOCs (Figure 1 b).We studied acetaldehyde removal at different concentrations to evaluate the efficacy of these materials in comparison with traditional amelioration methods, such as u...

Excellent catalytic performance, thermal stability, and water resistance of 3DOM Mn2O3-supported Au–Pd alloy nanoparticles for the complete oxidation of toluene

“…For example, the T 90% (temperature required for achieving a 90 % conversion of toluene) was 234 o C over Pd/Co 3 AlO [8], much lower than that (340 o C) over Co 3 AlO. Recently, gold-based catalysts have been found to be effective in toluene oxidation [10][11][12][13][14][15]. For instance, the T 90% for toluene oxidation was 182 and 170 o C over Au/γ-MnO 2 [11] and Au/La 0.6 Sr 0.4 MnO 3 [12], respectively.…”

“…Recently, gold-based catalysts have been found to be effective in toluene oxidation [10][11][12][13][14][15]. For instance, the T 90% for toluene oxidation was 182 and 170 o C over Au/γ-MnO 2 [11] and Au/La 0.6 Sr 0.4 MnO 3 [12], respectively. When water vapor is introduced into the reaction system, however, supported Pd or Au nanoparticle (NP) catalysts are not catalytically durable, thus limiting their applications.…”

Mesoporous Hydrous Manganese Dioxide Nanowall Arrays with Large Lithium Ion Energy Storage Capacities

“…Recently, successful fabrication of high-surface-area manganese dioxide following the template-free concept has been reported by Sinha et al by means of a wet precipitation method [27] and its application in extensive air purification has turned out to be a great success. However, manganese dioxide fabricated in this way is not suitable as large lithium-ion capacity storage device as the electrolyte penetration would be very difficult in such thick oxide films with small pores.…”

Sustainable Nanotechnology: Through Green Methods and Life-Cycle Thinking

“…Applications of nanotechnology that directly benefit the environment are nanotechnologies for site remediation and wastewater treatment [9], nanomaterial-based solar cells for improved energy efficiency, the use of nanocatalysts for air purification [10], and nanostructured filters or nanoreactive membranes for water purification [11].…”