Controllable Compositions and Structures of Fe_xO_y@SiO₂@C-Ni Hybrids with a Silica Layer as a Mineral Redox Buffer

Abstract

Mineral redox buffer is a vital concept in geology that can be applied to modulate hybrid compositions and generate nanostructures with expected morphology. Here, via combining a dual coating of an inorganic silica and organic resorcinol-formaldehyde-Ni2+ (RF-Ni2+) layer on α-Fe2O3 spindles with a subsequent calcination process, core–shell Fe x O y @SiO2@C-Ni composites with multicompositional structures were fabricated as efficient catalysts for 4-nitrophenol (4-NP) reduction. Notably, the silica layer as a redox buffer between hematite cores and the RF-Ni2+ shell played a crucial role in modulating the compositions and structures of the Fe x O y @SiO2@C-Ni. Without the silica layer, Fe3O4-Ni/C composites with Ni nanoparticles trapped into the Fe3O4 cores were generated. Moreover, a significant impact of the calcination temperature on morphologies and compositions of the Fe x O y @SiO2@C-Ni catalysts along with their catalytic performances has been verified. As a result, the catalyst annealed at 500 °C exhibited a high magnetic property and optimized morphology with high-density small nickel nanoparticles (∼11.6 nm), showing remarkably enhanced catalytic activity compared to the Fe3O4-Ni/C composites and excellent recyclability with a high conservation of about 92%. Furthermore, this synthetic strategy shows significant potential to modulate the nanostructures and phases of other multivalent metal oxide nanocomposites.

Facile fabrication of ultrafine CoNi alloy nanoparticles supported on hexagonal N-doped carbon/Al2O3 nanosheets for efficient protein adsorption and catalysis

“…The gradual appearance of a peak at 300 nm indicated the corresponding production of 4-aminophenol. 50–53 The reduction of 4-nitrophenol into 4-aminophenol in the presence of C–CoNi/Al 2 O 3 was completed in 15 min (Fig. 6A).…”

“…Recently, we have employed carbonized polydopamine (PDA) or RF polymer as a stabilizer and reductant for synthesizing Ni-based carbon composites in a nitrogen atmosphere. [28][29][30][31][32][33][34] Thanks to the reducing ability exhibited by these carbonized polymers, transition metal ions can be reduced to metallic NPs embedded in a carbon layer after carbonization treatment. Grounded on the above studies, herein, we report organic polymer (PDA-Ni 2+ ) coating coupled with post-carbonization treatment for the preparation of uniform sheet-like and multi-compositional structures of carbon layers embedded with CoNi NPs (denoted as C-NiCo/Al 2 O 3 ) using CoAl-LDH@PDA-Ni 2+ nanosheets as a precursor (Scheme 1).…”

Cu Nanoparticles Supported on Fe3O4@SiO2@N-Doped Carbon Core–Shell Nanocomposites for C–N Coupling Reactions in Water

“…Initially, uniform Fe 3 O 4 particles were prepared via a solvothermal reaction and were subsequently coated with a SiO 2 layer by a modified Stober process 43 to obtain the Fe 3 O 4 @SiO 2 core−shell microspheres. 44 The carbon precursors, such as glucosamine, glucose, and chitosan, were then added to chelate the metal NPs in order to introduce a variety of functional groups. Moreover, these groups were effectively retained after the HTC process.…”

“…The hydrothermal carbonization processes used to fabricate the Fe 3 O 4 @SiO 2 @C/Cu catalyst is illustrated in Scheme . Initially, uniform Fe 3 O 4 particles were prepared via a solvothermal reaction and were subsequently coated with a SiO 2 layer by a modified Stöber process to obtain the Fe 3 O 4 @SiO 2 core–shell microspheres . The carbon precursors, such as glucosamine, glucose, and chitosan, were then added to chelate the metal NPs in order to introduce a variety of functional groups.…”

A uniformly anchored zirconocene complex on magnetic reduced graphene oxide (rGO@Fe3O4/ZrCp2Clx(x= 0, 1, 2)) as a novel and reusable nanocatalyst for synthesis ofN-arylacetamides and reductive-acetylation of nitroarenes

“…These improvements have been made in order to increase the accessible sites/zones on the surface of catalyst, greater catalyst reactivity and selectivity, thermal stability and finally easy separation. Fe 3 O 4 , 12,13 NiFe 2 O 4 , 14–16 CoFe 2 O 4 , 17 CuFe 2 O 4 , 18–20 MnFe 2 O 4 , 21 Ni–Cu–ZnFe 2 O 4 , 22 BiFeO 3 , 23 FeAl 2 O 4 24 and ZnCrFeO 4 25 as a core, and metals, 26–28 silica, 29–32 polymers, 33–35 carbon nanotubes and sheets, 36–40 cellulose, 41 small organic molecules, 42,43 ionic liquids, 44,45 and organosulfonic acids 46,47 have been used as a coating.…”