Fabrication of ultrafine nickel nanoparticles anchoring carbon fabric composites and their High catalytic performance

Fe3O4 nanoparticles entrapped in the inner surfaces of N-doped carbon microtubes with enhanced biomimetic activity

Tubular structured composites have attracted great interest in catalysis research owing to their void-confinement effects. In this work, we synthesized a pair of hollow N-doped carbon microtubes (NCMTs) with Fe3O4 nanoparticles (NPs) encapsulated inside NCMTs (Fe3O4@NCMTs) and supported outside NCMTs (NCMTs@Fe3O4) while keeping other structural features the same. The impact of structural effects on the catalytic activities was investigated by comparing a pair of hollow-structured nanocomposites. It was found that the Fe3O4@NCMTs possessed a higher peroxidase-like activity when compared with NCMTs@Fe3O4, demonstrating structural superiority of Fe3O4@NCMTs. Based on the excellent peroxidase-like catalytic activity and stability of Fe3O4@NCMTs, an ultra-sensitive colorimetric method was developed for the detection of H2O2 and GSH with detection limits of 0.15 μM and 0.49 μM, respectively, which has potential application value in biological sciences and biotechnology.

Copper-Based Nanocatalysts with SiO2 and Carbon Dual-Layer Coatings and Metallic Ni/CuNi Decoration toward Highly Efficient Nitroaromatics Reduction

Nanocomposites with novel architectures and multifunctional properties have attracted extensive attention among related researchers. Herein, we develop a magnetically responsive Ni/CuNi nanoparticle (NP) decoration of Cu-based composites that could serve as recoverable nanocatalysts for nitroaromatics reduction. The nanocatalysts consist of an inner copper core and abundant tiny satellite Ni/CuNi NPs, which are tightly combined as a stable whole part by a silica interlayer and a carbon outer layer. In addition to the high catalytic activity, the outer Ni/CuNi NPs exhibit a strong magnetic response toward the external magnetic field, thereby offering a convenient way to separate the composites from the reaction solution. Moreover, characterization results reveal that high annealing temperature (above 700 °C) favors the construction of yolk-shell nanostructures and the formation of outer bimetallic CuNi NPs. As a result, owing to the excellent catalytic performance of the Cu inner cores, the high coverage of outer Ni or CuNi NPs, and the unique sandwich-like structure, the resultant Cu@SiO₂@C-Ni composites show the use of such magnetically responsive recoverable nanocatalysts for the 4-nitrophenol reduction. Hence, this research could provide new guidelines for designing and synthesizing novel and efficient copper-based composites for other fields, such as carbon dioxide reduction, energy storage, and batteries.

Rational design, synthesis, and applications of carbon-assisted dispersive Ni-based composites

Herein, we review recent developments in the rational design and engineering of various carbon-assisted dispersive nickel-based composites, and boosted properties for protein adsorption and nitroaromatics reduction.

Enhanced activity for reduction of 4-nitrophenol of Ni/single-walled carbon nanotube prepared by super-growth method

In this study, we synthesised the Ni/single-walled carbon nanotube prepared by the super-growth method (SG-SWCNTs). In this approach, the Ni nanoparticles were immobilised by an impregnation method using the SG-SWCNTs with high specific surface areas (1144 m²g^-1). The scanning electron microscopy images confirmed that the SG-SWCNTs exhibit the fibriform morphology corresponding to the carbon nanotubes. In addition, component analysis of the obtained samples clarified that the Ni nanoparticles were immobilised on the surface of the SG-SWCNTs. Next, we evaluated the activity for the reduction of 4-nitoropenol in the presence of the Ni/SG-SWCNTs. Additionally, the Ni/graphene, which was obtained by the same synthetic method, was utilised in this reaction. The rate of reaction activity of the Ni/SG-SWCNTs finished faster than that of the Ni/GPs. From this result, the pseudo-first-order kinetic rate constantkfor the Ni/SG-SWCNTs and the Ni/GPs was calculated respectively at 0.083 and 0.070 min^-1, indicating that the Ni/SG-SWCNTs exhibits higher activity.

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

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_xO_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_xO_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_xO_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.

Constructing Ultrathin W-Doped NiFe Nanosheets via Facile Electrosynthesis as Bifunctional Electrocatalysts for Efficient Water Splitting

Exploring cost-effective and efficient bifunctional electrocatalysts via simple fabrication strategies is strongly desired for practical water splitting. Herein, an easy and fast one-step electrodeposition process is developed to fabricate W-doped NiFe (NiFeW)-layered double hydroxides with ultrathin nanosheet features at room temperature and ambient pressure as bifunctional catalysts for water splitting. Notably, the NiFeW nanosheets require overpotentials of only 239 and 115 mV for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, to reach a current density of 10 mA/cm² in alkaline media. Their exceptional performance is further demonstrated in a full electrolyzer configuration with the NiFeW as both anode and cathode catalysts, which achieves a low cell voltage of 1.59 V at 10 mA/cm², 110 mV lower than that of the commercial IrO₂ (anode) and Pt (cathode) catalysts. Moreover, the NiFeW nanosheets are superior to various recently reported bifunctional electrocatalysts. Such remarkable performances mainly ascribe to W doping, which not only effectively modulates the electrocatalyst morphology but also engineers the electronic structure of NiFe hydroxides to boost charge-transfer kinetics for both the OER and HER. Hence, the ultrathin NiFeW nanosheets with an efficient fabrication strategy are promising as bifunctional electrodes for alkaline water electrolyzers.

A facile template method to fabricate strongly coupled 1D sandwich-like C@Fe3O4@C/Ni coaxial microtubes with enhanced catalytic performance

Sandwich-like C@Fe₃O₄@C/Ni microtubes were well-constructed with MoO₃ microrods as a hard template, which manifested excellent catalytic performance and recycling ability in the reduction of 4-nitrophenol.