Synthesis of high surface area CuMn2O4 by supercritical anti-solvent precipitation for the oxidation of CO at ambient temperature

Abstract

A series of high surface area nanocrystalline copper manganese oxide catalysts have been prepared by supercritical anti-solvent (SAS) precipitation using CO 2 and tested for the ambient temperature oxidation of CO. The catalysts were prepared by precipitation from an ethanol/metal acetate solution and the addition of small quantities of water was found to result in a mixed acetate precursor with surface areas 4200 m 2 g À1 , considerably higher than those prepared by conventional precipitation methods. The surface area of the final calcined mixed oxide was found to be dependent upon the initial water concentration. XRD and FT-IR analysis indicated that the addition of water promoted the formation of carbonate species in the amorphous acetate precursor, with high resolution TEM and STEM showing the material to consist of spherical agglomerations of fibrous strings of ca. 30 nm length. This is in contrast to the material prepared in the absence of water, using the same SAS methodology, which typically yields quasi-spherical particles of 100 nm size.

Supercritical antisolvent precipitation of TiO2 with tailored anatase/rutile composition for applications in redox catalysis and photocatalysis

“…Further studies into oxidation catalysts synthesised using SAS precipitation, such as vanadium phosphates, Co 3 O 4 and CuMnO 4 , have shown that poorly crystalline nanocrystalline materials with good redox properties and high activity for a range of reactions [30][31][32]. Studies have also been performed on the SAS preparation of TiO 2 in both batch and semi-continuous modes using acetylacetonate and alkoxide precursors [33][34][35][36].…”

Effect of Preparation Conditions on the Catalytic Activity of CuMnOx Catalysts for CO Oxidation

“…It can be seen from the Figure 9, that the activity of resulting catalyst increases with the increasing drying temperature of the precursor up to 110 o C, and further increasing the drying temperature, the activity decreases. Thus, the optimum drying temperature of the precursor is 110 o C, which produced the catalyst exhibiting the highest activity for 100 % CO conversion at 120 o C. The temperature at which precipitation is carrying out does not significantly affect the bulk (Cu:Mn) ratio of the precipitate [37].…”

“…The catalyst calcined at 300 o C for 2 h showed the best catalytic activity for complete oxidation of CO at 120 o C temperature. The increasing calcination temperature raises the oxidation of excess Cu 2+ ions and decreases the concentration of surface oxygen vacancies; as a result the formation of stoichiometric CuMnOx catalyst [37,38].…”

Simple synthetic route to manganese-containing nanowires with the spinel crystal structure

“…Spinels such as Fe 3 O 4 [1,2] Mn 3 O 4 [3,4] and LiMn 2 O 4 [5,6] for example, are known to perform well as electrodes for lithium ion batteries; of particular interest are the tests performed by Thackeray et al [7] and Feltz et al [8] who tested the lithiation kinetics for manganese-containing spinels MMn 2 O 4 (M ¼ Mn, Mg, Li), and found that the reducibility of the manganese cations was a crucial factor for lithiation. Besides their use as battery electrodes, manganese based spinels are also good catalysts for oxidation and reduction reactions: [9] CdMn 2 O 4 can be used as an electrode material for NO gas sensors; [10] NiMn 2 O 4 [11], mesoporous MnCo 2 O 4 [12], and high surface area CuMn 2 O 4 [13] have been shown to catalyze CO oxidation at ambient temperatures, exhibiting robust stabilities. Cu-Mn spinel oxides are also highly active for production of H 2 from methanol [14].…”

“…In this tetragonal spinel, Cu þ , Cu 2 þ , Mn 2 þ , Mn 3 þ ions all take tetrahedral sites, with octahedral sites occupied by Cu 2 þ , Cu 3 þ , Mn 3 þ , Mn 4 þ . In its bulk form, CuMn 2 O 4 is known to catalyze the oxidation of CO to CO 2 at room temperature [13,36,37], and the reduction of NO x [38].…”