Ordered Mesoporous Ni Nanowires with Enhanced Hydrogenation Activity Prepared by Electroless Plating on Functionalized SBA-15

Highly ordered mesoporous Ni nanowires were synthesized by Ni electroless plating on the amine-functionalized SBA-15 (NH2−SBA-15) support, followed by removing the silica template with NaOH. The incorporation of amine groups into the pore channels and the subsequent activation of NH2−SBA-15 with PdCl2 acetone solution are essential for generating Pd crystal seeds distributed in the pore channels. As a result, the following Ni electroless plating occurred mainly in pore channels, leading to the formation of ordered Ni nanowires catalyst with high surface area, ordered mesopore arrangement, and higher activity than Raney Ni in liquid-phase p-chloronitrobenzene hydrogenation

KOH-Assisted Band Engineering of Polymeric Carbon Nitride for Visible Light Photocatalytic Oxygen Reduction to Hydrogen Peroxide

Visible light-driven photocatalytic production of H2O2 from molecular oxygen represents a promising route to transform solar energy to green oxidants and solar fuels. Herein, KOH-assisted thermal polymerization of urea was adopted to controllably incorporate cyano groups into the polymeric carbon nitride (PCN) framework. Photoelectrical techniques and density functional theory (DFT) calculations disclosed that the cyano groups effectively narrow down the band gap, elevate the conduction band, and improve the generation, transmission, and lifetime of the photoexcited charge carriers, which synergistically boost the H2O2 productivity by up to 5.4 times with respect to that on the pristine PCN in photocatalytic reduction of molecular oxygen under visible light at room temperature. This facile and effective strategy to enhance the photocatalytic activity of the inexpensive PCN catalyst under visible light enriches the horizon of H2O2 production in an economic, safe, and environmentally benign manner

Controlled Synthesis, Characterization, and Crystallization of Ni−P Nanospheres

The size- and composition-controlled synthesis of Ni−P nanospheres from nickel chloride and sodium hypophosphite has been systematically investigated by changing the conditions, such as the ratio of the starting materials, pH value, and reduction temperature. It was found that when the starting ratio of H2PO2-/Ni2+ was changed the size and chemical composition of the nanoparticles changed simultaneously. Within a suitable pH range, the phosphorus content was altered without affecting the particle size. Increasing the reduction temperature resulted in smaller Ni−P nanospheres but invariable phosphorus content. The Ni−P nanospheres were amorphous when the phosphorus content was higher than 10.0 mol %, while lower phosphorus content led to a composite of amorphous Ni−P and face-centered cubic (fcc) Ni. During postsynthesis calcinations, amorphous Ni−P nanospheres with a low phosphorus content directly crystallized to Ni3P and fcc Ni. However, the specimens with high phosphorus content crystallized via some intermediate phases such as Ni5P2 and Ni12P5. In the latter, an amorphous P-rich shell was developed simultaneously. A preliminary catalytic test of growth of carbon nanofibers on the Ni−P nanospheres has been carried out

A General Chelate-Assisted Co-Assembly to Metallic Nanoparticles-Incorporated Ordered Mesoporous Carbon Catalysts for Fischer–Tropsch Synthesis

The organization of different nano objects with tunable sizes, morphologies, and functions into integrated nanostructures is critical to the development of novel nanosystems that display high performances in sensing, catalysis, and so on. Herein, using acetylacetone as a chelating agent, phenolic resol as a carbon source, metal nitrates as metal sources, and amphiphilic copolymers as a template, we demonstrate a chelate-assisted multicomponent coassembly method to synthesize ordered mesoporous carbon with uniform metal-containing nanoparticles. The obtained nanocomposites have a 2-D hexagonally arranged pore structure, uniform pore size (∼4.0 nm), high surface area (∼500 m²/g), moderate pore volume (∼0.30 cm³/g), uniform and highly dispersed Fe₂O₃ nanoparticles, and constant Fe₂O₃ contents around 10 wt %. By adjusting acetylacetone amount, the size of Fe₂O₃ nanoparticles is readily tunable from 8.3 to 22.1 nm. More importantly, it is found that the metal-containing nanoparticles are partially embedded in the carbon framework with the remaining part exposed in the mesopore channels. This unique semiexposure structure not only provides an excellent confinement effect and exposed surface for catalysis but also helps to tightly trap the nanoparticles and prevent aggregating during catalysis. Fischer–Tropsch synthesis results show that as the size of iron nanoparticles decreases, the mesoporous Fe–carbon nanocomposites exhibit significantly improved catalytic performances with C₅₊ selectivity up to 68%, much better than any reported promoter-free Fe-based catalysts due to the unique semiexposure morphology of metal-containing nanoparticles confined in the mesoporous carbon matrix

Fe_<i>x</i>O_<i>y</i>@C Spheres as an Excellent Catalyst for Fischer−Tropsch Synthesis

FexOy@C Spheres as an Excellent Catalyst for Fischer−Tropsch Synthesi

Effect of Titania Polymorphs on the Structure and Catalytic Performance of the Pt–WO_<i>x</i>/TiO₂ Catalyst in Glycerol Hydrogenolysis to 1,3-Propanediol

Catalytic hydrogenolysis of biomass-derived glycerol to 1,3-propanediol (1,3-PDO) represents an important process for the sustainable production of value-added chemicals. However, there is a dearth of understanding of the effect of the polymorph of the support on this reaction. Herein, two Pt–WOx/TiO2 catalysts supported on rutile TiO2 (r-TiO2) and anatase TiO2 (a-TiO2) polymorphs were prepared to investigate the crystal phase effect of TiO2 on the structural property and catalytic performance in glycerol hydrogenolysis. The TiO2 polymorph was identified to impose profound effects on the size of the Pt nanoparticles (NPs) and the dispersion and location of the WOx species, which originated from the discrepancies in the crystal structures between the PtO2 and the TiO2 polymorphs and the discrepancies in the interactions of WOx with different TiO2 polymorphs. In glycerol hydrogenolysis, the Pt–WOx/r-TiO2 catalyst gave a 1,3-PDO selectivity of 51.2% at a glycerol conversion to liquid products of 74.5%, yielding 38.1% of 1,3-PDO. In contrast, the Pt–WOx/a-TiO2 catalyst showed much inferior glycerol conversion and 1,3-PDO selectivity, yielding only 1.0% of 1,3-PDO under identical reaction conditions. The superior catalytic performance of the Pt–WOx/r-TiO2 catalyst is attributed to the r-TiO2 polymorph that facilitates a faster hydrogen spillover than the a-TiO2 polymorph from the Pt NPs to the reaction intermediate on the WOx species, which is substantiated by an even higher 1,3-PDO yield of 44.8% over the physically mixed Pt/r-TiO2 + WOx/r-TiO2 catalyst. This work demonstrates the critical role of the polymorph of the TiO2 support in the design of efficacious Pt–WOx-based catalysts for glycerol hydrogenolysis to 1,3-PDO

In-Situ Crystallization Route to Nanorod-Aggregated Functional ZSM‑5 Microspheres

Herein, we develop a reproducible in situ crystallization route to synthesize uniform functional ZSM-5 microspheres composed of aggregated ZSM-5 nanorods and well-dispersed uniform Fe3O4 nanoparticles (NPs). The growth of such unique microspheres undergoes a NP-assisted recrystallization process from surface to core. The obtained magnetic ZSM-5 microspheres possess a uniform size (6–9 μm), ultrafine uniform Fe3O4 NPs (∼10 nm), good structural stability, high surface area (340 m2/g), and large magnetization (∼8.6 emu/g) and exhibit a potential application in Fischer–Tropsch synthesis

Fischer–Tropsch Synthesis to Lower Olefins over Potassium-Promoted Reduced Graphene Oxide Supported Iron Catalysts

Fischer–Tropsch synthesis to lower olefins (FTO) opens up a compact and economical way to the production of lower olefin directly from syngas (CO and H₂) derived from natural gas, coal, or renewable biomass. The present work is dedicated to a systematic study on the effect of K in the reduced graphene oxide (rGO) supported iron catalysts on the catalytic performance in FTO. It is revealed that the activity, expressed as moles of CO converted to hydrocarbons per gram Fe per second (iron time yield to hydrocarbons, termed as FTY), increased first with the content of K, passed through a maximum at 646 μmol_CO g_Fe^–1 s^–1 over the FeK1/rGO catalyst, and then decreased at higher K contents. Unlike the evolution of the activity, the selectivity to lower olefins increased steadily with K, giving the highest selectivity to lower olefins of 68% and an olefin/paraffin (O/P) ratio of 11 in the C₂–C₄ hydrocarbons over the FeK2/rGO catalyst. The volcanic evolution of the activity is attributed to the interplay among the positive effect of K on the formation of Hägg carbide, the active phase for FTO, and the negative roles of K in increasing the size of Hägg carbide at high content and blocking the active phase by K-induced carbon deposition. The monotonic increase in the selectivity to lower olefins is ascribed to the improved chain-growth ability and surface CO/H₂ ratio in the presence of K, which favorably suppressed the unwanted CH₄ production and secondary hydrogenation of lower olefins

Porous Graphene-Confined Fe–K as Highly Efficient Catalyst for CO₂ Direct Hydrogenation to Light Olefins

We devised iron-based catalysts with honeycomb-structured graphene (HSG) as the support and potassium as the promoter for CO₂ direct hydrogenation to light olefins (CO₂–FTO). Over the optimal FeK1.5/HSG catalyst, the iron time yield of light olefins amounted to 73 μmol_CO2 g_Fe^–1 s^–1 with high selectivity of 59%. No obvious deactivation occurred within 120 h on stream. The excellent catalytic performance is attributed to the confinement effect of the porous HSG on the sintering of the active sites and the promotion effect of potassium on the activation of inert CO₂ and the formation of iron carbide active for CO₂–FTO