In situ redox strategy for large-scale fabrication of surfactant-free M-Fe2O3 (M = Pt, Pd, Au) hybrid nanospheres

Abstract

effects the catalytic activities, stabilities and selectivity of noble metals can be further optimized [31][32][33]. Among the substrates, magnetic oxides are more attractive on accounts of their excellent magnetic response [34][35][36][37][38][39][40]. Once noble metals are loaded on the magnetic oxide substrates to form stable hybrids, the fast separation of catalyts can be easily achieved from the reaction systems, which will favor simplifing the post-treatment to improve the recyclability.In previous reports, four main kinds of iron oxides supported noble metal nanostructures have been successfully fabricated. One is the simple Fe 3 O 4 /noble met al hybrids, in which noble metal components were evenly dispersed in the Fe 3 O 4 structures [41,42]. The second is the Janus nanostructure. The representive research were done by Sun's group that they realized the synthesis of colloidal dumbbell-like noble metal-Fe 3 O 4 hybrids in an oil phase via the classic seeding growth method [34][35][36][37][38]. The third is in a more complex core@shell nanostructure. Yin et al. [39] presented a water-phase strategy to prepare Fe 3 O 4 @SiO 2 @ Au@SiO 2 multi-layered core@shell nanostructure. For the last, noble metal salts and organometallic precursors were reduced at the same time to form noble metal/Fe alloys, and further oxidizing process resulted in the iron oxides coated noble metals nanostructures. Such obtained four kinds of hybrids are of high quaility, however the oil-phase synthesis makes the post-treatment a little onerous, and some indispensable expensive ligands increase the overall cost [43,44].Ideally, a promising method should be green and suitable for mass production of noble metal catalysts under mild conditions. Moreover, it should decrease and even deny the usage of toxic organic solvents and surfactants. Compared ABSTRACT A facile in situ redox strategy has been developed to fabricate surfactant-free M-Fe2O3 (M = Pt, Pd, Au) hybrid nanospheres. In this process, noble metal salts were directly reduced by the pre-prepared Fe3O4 components in an alkaline aqueous solution without using organic reductants and surfactants. During the redox reaction, Fe3O4 was oxidized into Fe2O3, and the reduzates of noble metal nanoparticles were deposited on the surface of the Fe2O3 nanospheres. Then the characterizations were discussed in detail to study the formation of M-Fe2O3 hybrids. At last, catalytic CO oxidation was selected as a model reaction to evaluate the catalytic performance of these samples. It demonstrates that Pt-Fe2O3 nanospheres can catalyze 100 % conversion of CO into CO2 at 90°C, indicating superior activity relative to Pd-Fe2O3 and Au-Fe2O3.

Self‐Assembled Pd@CeO2/γ‐Al2O3 Catalysts with Enhanced Activity for Catalytic Methane Combustion

“…Noble metals supported on metal oxides have been proved as highly active for catalyzing methane combustion because the support can strongly interact with noble metals and also improve their dispersity . Pd, as a classic kind of oxidation catalysts, often exhibits much higher catalytic activity compared to other noble metals, because Pd and PdO could readily interconvert during catalytic processes and, moreover, strongly synergistic effects exist between Pd species and supports .…”

High‐Performance Ultrathin Co3O4 Nanosheet Supported PdO/CeO2 Catalysts for Methane Combustion

“…However, these strategies brought an obvious drawback that the as‐obtained Pd nanocatalysts with overexposed active centers often exhibited unsatisfied thermal stability caused by sintering. To solve this problem, kinds of Pd@MO x core(yolk)@shell nanostructures and Pd‐metal alloys have been successfully investigated to improve anti‐sintering ability of Pd despite the catalytic active centers might be partially blocked, so it seems hard to reconcile activity and stability. Moreover, most of the Pd@MO x core@shell nanostructures and Pd‐metal alloys are prepared by toxic and complex organic routes that limit mass production for application.…”

Toxic effects of metal oxide nanoparticles and their underlying mechanisms

“…Owing to excellent biocompatibility, IONPs have been frequently used in biomedical fields [74][75][76]. The term IONPs include both superparamagnetic iron oxide nanoparticles (SPION) and magnetic IONPs, among which hematite (α-Fe2O3), maghemite (γ-Fe2O3), and magnetite (Fe3O4) are the most common.…”