Hydrogenation Of P-nitrophenol Research Articles

Catalytic Performance in Nitroarene Reduction of Nanocatalyst Based on Noble Metal Nanoparticles Supported on Polymer/s-Layer Protein Hybrids.

We present a novel bionanocatalyst fabricated by the adsorption-reduction of metal ions on a polyurethane/S-layer protein biotemplate. The bioinspired support was obtained by the adsorption of S-layer proteins (isolated from Lentilactobacillus kefiri) on polyurethane particles. Silver and platinum nanoparticles were well-loaded on the surface of the support after the combination with metallic salts and reduction with H2 at room temperature. Transmission electron microscopy analysis revealed the strawberry-like morphology of the bionanocatalysts with a particle size, dn, of 2.39 nm for platinum and 9.60 nm for silver. Both systems catalyzed the hydrogenation of p-nitrophenol to p-aminophenol with high efficiency in water at mild conditions in the presence of NaBH4. Three different amounts of bionanocatalyst were tested, and in all cases, conversions between 97 and 99% were observed. The catalysts displayed excellent recyclability over ten cycles, and no extensive damage in their nanostructure was noted after them. The bionanocatalysts were stable during their production, storage, and use, thanks to the fact that the biosupport provides an effective driving force in the formation and stabilization of the metallic nanoparticles. The successful bioinspired production strategy and the good catalytic ability of the systems are encouraging in the search for nontoxic, simple, clean, and eco-friendly procedures for the synthesis and exploitation of nanostructures.

Emulsion Liquid Membranes Based on Os-NP/n-Decanol or n-Dodecanol Nanodispersions for p-Nitrophenol Reduction.

Membrane materials with osmium nanoparticles have been recently reported for bulk membranes and supported composite membrane systems. In the present paper, a catalytic material based on osmium dispersed in n-decanol (nD) or n-dodecanol (nDD) is presented, which also works as an emulsion membrane. The hydrogenation of p-nitrophenol (PNP) is carried out in a reaction and separation column in which an emulsion in the acid-receiving phase is dispersed in an osmium nanodispersion in n-alcohols. The variables of the PNP conversion process and p-aminophenol (PAP) transport are as follows: the nature of the membrane alcohol, the flow regime, the pH difference between the source and receiving phases and the number of operating cycles. The conversion results are in all cases better for nD than nDD. The counter-current flow regime is superior to the co-current flow. Increasing the pH difference between the source and receiving phases amplifies the process. The number of operating cycles is limited to five, after which the regeneration of the membrane dispersion is required. The apparent catalytic rate constant (kapp) of the new catalytic material based on the emulsion membrane with the nanodispersion of osmium nanoparticles (0.1 × 10-3 s-1 for n-dodecanol and 0.9 × 10-3 s-1 for n-decanol) is lower by an order of magnitude compared to those based on adsorption on catalysts from the platinum metal group. The advantage of the tested membrane catalytic material is that it extracts p-aminophenol in the acid-receiving phase.

High-Entropy Alloy Al0.2Co1.5CrFeNi1.5Ti0.5 Prepared from High-Entropy Oxide (Al0.2Co1.5CrFeNi1.5Ti0.5)3O4 by a Deoxidation Process via a CaH2-Assisted Molten Salt Method

High-entropy alloys (HEAs) have attracted a great deal of research interest these days because of their attractive properties. Low-temperature chemical synthesis methods are being developed to obtain nanoscale HEAs with low energy consumption. In this study, we prepared HEA Al0.2Co1.5CrFeNi1.5Ti0.5 nanoparticles from high-entropy oxide (HEO) (Al0.2Co1.5CrFeNi1.5Ti0.5)3O4 by a deoxidation process via a CaH2-assisted molten salt method at 600 °C. X-ray diffraction measurements demonstrated that the oxide precursor and the reduced product have single-phases of spinel structure and face-centered cubic structures, indicating the formation of HEO and HEA, respectively. The HEA nanoparticles exhibited superior catalytic performance in the liquid-phase hydrogenation of p-nitrophenol at room temperature with little leaching of the component elements. Scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDX) exhibited a good distribution of constituent elements over the HEA nanoparticles in a micro-sized range. However, transmission electron microscopy (TEM) with EDX revealed a slight deviation of elemental distributions of Al and Ti from those of Co, Cr, Fe, and Ni in a nano-sized range, probably due to the incomplete reduction of aluminum and titanium oxides. The elemental homogeneity in the HEA nanoparticles could be improved by taking advantage of the HEO precursor with homogeneous elemental distributions, but the experimental results suggested the importance of the total reduction of oxide precursors to prepare homogeneous HEAs from HEOs.

Low-cost and highly stable Ni@NC materials synthesized from metal-organic framework precursors for selectively catalytic hydrogenation of p-nitrophenol under mild conditions

The catalytic hydrogenation of aromatic nitro compounds under mild conditions to generate amino compounds is a great challenge in terms of conversion, selectivity and stability. In this paper, two classes of nitrogen-doped carbon coated nickel nanoparticles, coined Ni@NC-P and displaced Ni@NC-T were prepared by high-temperature pyrolysis of MOFs using inexpensive terephthalic acid and high-priced trimesic acid as carbon source, respectively. One from the former class, namely the Ni@NC-P-500 catalyst, exhibits the best catalytic performance, which is superior to Ni@NC-T-500 Samples. For the selective hydrogenation of p-nitrophenol under mild conditions (60 °C, 2 h), the Ni@NC-P-500 catalyst shows >99.9 % conversion of p-nitrophenol and >99.9 % selectivity for p-aminophenol and can be recycled five times without obvious decrease of conversion and selectivity, thanks to its larger specific surface area (382.02 m2·g−1), smaller nickel particle size (8.2 nm), higher nitrogen content (especially pyridine nitrogen), higher electron-rich nickel content and less hydrophilic properties than that of the Ni@NC-T-500. The excellent stability and recyclability of the catalysts are mainly attributed to their core–shell structure, i.e., zero-valent nickel nanoparticles encapsulated within a nitrogen-doped carbon layer with an appropriate microporous structure, whereas zero-valent nickel nanoparticles have the ability to activate dihydrogen and block dioxygen.

Graphene Chainmail Shelled Dilute Ni─Cu Alloy for Selective and Robust Aqueous Phase Catalytic Hydrogenation.

Cost-effective non-noble metal-based catalysts for selective hydrogenation with excellent activity, selectivity, and durability are still the holy grail. Herein, an oxygen-doped carbon (OC) chainmail encapsulated dilute Cu-Ni alloy is developed by simple pyrolysis of Cu/Ni-metal-organic framework. The CuNi0.05@OC catalyst displays superior performance for atmospheric pressure transfer hydrogenation of p-chloronitrobenzene and p-nitrophenol, and for hydrogenation of furfural, all in water and with exceptional durability. Comprehensive characterizations confirm the close interactions between the diluted Ni sites, the base Cu, and optimized three-layered graphene chainmail. Theoretical calculations demonstrate that the properly tuned lattice strain and Schottky junction can adjust electron density to facilitate specific adsorption on the active centers, thus enhancing the catalytic activity and selectivity, while the OC shell also offers robust protection. This work provides a simple and environmentally friendly strategy for developing practical heterogeneous catalysts that bring the synergistic effect into play between dilute alloy and functional carbon wrapping.

Constructing fully exposed Pt atomically dispersed catalysts for enhanced multifunctional selective hydrogenation reactions

Constructing highly efficient and low-cost catalysts is essential for the selective hydrogenation reaction. Herein, we developed fully exposed Pt atomically dispersed catalysts (PtAD/C-Al2O3) by a simple carbon modified strategy. Importantly, the co-existence of Pt-O1C2 single atoms and Pt nanoclusters in the PtAD/C-Al2O3 system could exhibit excellent catalytic activity in the selective hydrogenation of quinoline and p-nitrophenol. Notably, the quinoline conversion and the corresponding selectivity of 1,2,3,4-tetrahydroquinoline is 99.6 % and 99.3 %, respectively. Meanwhile, the turnover frequency of PtAD/C-Al2O3 (1081 h−1) is 3.8 and 5.7 times higher than that of Pt single-atom catalysts (PtSA/C-Al2O3) and Pt nanoparticles (PtNPs/C-Al2O3), respectively, during quinoline hydrogenation. Besides, the rate constant of PtAD/C-Al2O3 could reach 192.5 min-1mgPt-1 for p-nitrophenol hydrogenation, which is much better than most of the reported catalysts. Mechanism studies revealed the synergistic effect between Pt-O1C2 single atoms and Pt nanoclusters acts as the main role in enhancing the hydrogenation activity. Specifically, Pt single atoms sites mainly adsorb and activate quinoline molecules, while Pt nanoclusters boost the dissociation of H2 molecules to H atoms. This work paves an origin carbon modified method to construct Pt atomically dispersed catalysts for efficient multifunctional hydrogenation.

A CaH2-Assisted Reduction Method to Prepare Nanoscale Zero-Valent Iron (nZVI) from Fe2O3 for Water Remediation Application

In recent decades, nanoscale zero-valent iron (nZVI) has been extensively studied for application in environmental remediation because it is an eco-friendly, inexpensive nanomaterial with high reactivity. The chemical reduction of iron ions using NaBH4 in a liquid solution is the most frequently used method to obtain nZVI, but its drawbacks are the use of expensive and toxic NaBH4 and the secondary pollution caused by the B(OH)3 by-product. In this study, in order to obtain nZVI in a cleaner manner, we used a reduction method for Fe2O3 using CaH2, which is non-toxic and generates no pollutants. The results of X-ray diffraction, nitrogen adsorption, and scanning electron microscopy for the obtained samples indicated the formation of zero-valent iron nanopowder (22.5 m2/g) that was obtained via reduction at 220 °C for 5 h. The obtained nZVI was finally tested in the catalytic hydrogenation of p-nitrophenol as a model reaction of water remediation, verifying its good catalytic performance.

The synergy of Co-MoN-MgO on 2D carbon sheets for effective catalytic hydrogenation

The Co-based materials are the promising catalysts for the catalytic hydrogenation reactions. The optimization of the electronic structure and micro-morphology to achieve like-noble-metal catalysis is a current research hotspot. Here, the Co-MoN-MgO heterojunctions embedded on 2D carbon nanosheets (Co-MoN-MgO/C) were designed in a melt-salt system for efficient catalytic hydrogenation of the nitro-compounds. The tests show the intimate contact of Co with MoN, realizing effective synergy for promoting the electrons transfer from Co to MoN. The transfer optimizes the electronic structure of Co components, being favorable for the adsorption/desorption of intermediates and catalytic hydrogenation reaction. The 2D porous structure gives enhanced mass-transfer ability and large accessible surface for better contact with the reactants. Above features endow Co-MoN-MgO/C with good catalytic activity for p-nitrophenol (4-NP) hydrogenation, with a reaction rate constant k of 0.41 min−1 (10 °C), which is 2.73 times greater than Co-MgO/C catalyst (0.15 min−1) and even better than some reported noble-metal catalysts. Furthermore, the catalyst shows good cycling stability with no obvious deactivation after 10 cycles and obvious catalytic activity for a series of nitro-compounds. This work has important implications for the design of efficient non-noble-metal synergistic catalyst for the effective catalytic hydrogenation.

Novel, Biosynthesis of Palladium Nanoparticles using Strychnos Potatorum Polysaccharide as a Green sustainable approach; and their effective Catalytic Hydrogenation of 4-Nitrophenol

In the current study, we successfully used strychnos potatorum polysaccharide through autoclaving to synthesize palladium nanoparticles in a green, sustainable process. These polysaccharide act as a stabilizing, capping, and reducing agent. It also used various analytical characterizations, including UV–Visible spectroscopy, FT-IR spectroscopy, X-Ray diffraction (XRD), Scanning electron microscopy (FE-SEM), EDAX, and X-ray photoelectron spectroscopy (XPS), TEM and gel permeation chromatography (GPC) are used to analyze biosynthesized pallidum nanoparticles (PdNPs). The surface plasmon resonance (SPR) band at 276 nm and UV–visible spectroscopy revealed the presence of the generated PdNPs. The XRD data show that PdNPs have crystalline behavior and a pristine face-centered cubic (FCC) structure. The PdNPs were successfully developed by catalytic reduction of 4-nitrophenol (4-NP). The catalytic activity and reusability of the environmentally friendly PdNPs catalyst were demonstrated by achieving a remarkable transformation of 95 % nitrophenol to 4-aminophenol after five cycles. The reaction rate constant (k) for the degradation of 4-nitrophenol (4-NP) using SP-PdNPs as a catalyst is 0.1201 min−1 and R2 0.9867, with a normalized rate constant of (Knor = K/m) of 7.206 s−1 mM−1. These findings provide fundamental knowledge of the catalytic process governing the hydrogenation of p-nitrophenol, which will help designers of effective catalysts. An innovative and affordable technique for creating PdNPs that are environmentally acceptable and can be utilized as effective catalysts in environmental applications is the use of strychnos potatorum gum polysaccharide. The green-synthesized PdNPs can be used for pollutant remediation, including pharmaceutical, domestic, heavy metal, industrial, and pesticide pollutants.

Rationally engineering magadiite heavy metal adsorbent for p-nitrophenol hydrogenation reduction

The reutilization of spent heavy metal adsorbents as efficient heterogeneous catalysts is of great interests but remains a great challenge. In this work, cetyltrimethyl ammonium bromide intercalated magadiite (Mag) is facilely synthesized via cation exchange reaction, which possesses good uptake capacity towards metal ions and high structural stability. As a case study, these spent adsorbents loaded by Ag+, Zn2+, and Cu2+ species are recycled to construct nanohybrids MeOx-Mag and Me0-Mag (Me = Ag, Cu, and Zn) by calcining the exhausted solids under air and H2/Ar (5 vol% H2), respectively. The resultant imperfect pillared solids still inherit the interlayer space and nanosheet morphology from their Mag precursors, which is verified by abundant microscopic and spectroscopic characterizations. Importantly, Cu0 nanoparticle modified Mag (CuM) exhibits remarkable catalytic activity for a p-nitrophenol (p-NP) hydrogenation reduction. 100% p-NP (60 mL, 20 mg/L) can be converted into p-aminophenol (p-AP) within 30 min when 2 mg CuM is used with the assistance of 10 mg NaBH4. Discrete Cu0 nanoparticles promote the generation of active H⁎ and thus the heterogeneous catalysis for p-AP products. The catalytic performance with important parameters (Cu0 loading amount, p-NP initial concentration, NaBH4 addition dosage, etc.) is discussed extensively to understand how to prefer reaction conditions for optimum nitro hydrogenation performance. The present study provides a rational design of spent Mag-based adsorbents for advanced environmental and catalysis applications via exploring the potential value of solids post-use.

Green synthesis of Multifunctional Zinc oxide Nanoparticles from Cordia myxa gum; and their Catalytic Reduction of Nitrophenol, Anticancer and Antimicrobial Activity

In situ exfoliated natural polysaccharide Cordia myxa (CMX) is used to promote the utilization of zinc-oxide nanoparticles for eco-friendly catalytic hydrogenation of p-nitrophenol (p-NP) and microbial growth inhibition. Polysaccharide-mediated biosynthetic nanocomposite materials are interesting because they are cheap, green, and environmentally friendly. This study uses CMX gum as a bioreduction to produce multifunctional, environmentally friendly zinc-oxide nanocomposites (ZnO NPs). The process involves a low reaction time and temperature and utilizes CMX as a reducing and stabilizing agent. The structural, morphological, and optical properties of the CMX-ZnO nanocomposite were characterized. The biosynthetic CMX-ZnO NPs exhibited robust catalytic activity and recycling capacity for rapidly oxidizing hazardous p-NPs. The complete reduction of 4-NP to CMX-ZnO NPs in excess NaBH4 was achieved within 15 min, with recyclability and pseudo-first-order kinetics with a rate constant of 0.2571 min−1. Additionally, human colon cancer (HCT116) and 3T3L1 cell lines were remarkably sensitive to the cytotoxic effects of ZnO nanoparticles. CMX-ZnO NPs exhibited potent antibacterial properties against human pathogenic gram-positive and gram-negative bacteria (Bacillus, Salmonella, E. coli, and Pseudomonas aeruginosa) based on the zone of inhibition measured by the disc-diffusion method. The significant antibacterial activity of CMX-ZnO NPs can overcome the current limitations associated with removing water-soluble organic pollutants and microbiological contaminants for long-term environmental sustainability.

Clay-based durable catalyst membranes of porous layered double hydroxide and gold nanoparticle nanocomposites for fast and continuous-flow reactions

We synthesized the hybrid catalyst of a porous layered double hydroxide (LDH) decorated with ultrasmall Au nanoparticles. The porous LDH was prepared by coprecipitation and ethanol washing, producing thin LDH nanoplatelets. Thereafter, spray drying was carried out, affording a few hundred nm of the hydrangea-like structure of the LDH with an extensive open network and a Brunauer–Emmett–Teller surface area of 386 m2/g. Its sizable open frame and active hydroxide surface enabled the uniform decoration of average 4-nm-diameter Au nanoparticles (Au/P-LDH) through one-pot chemical reduction using NaBH4 at room temperature. We applied the Au/P-LDH for the fabrication of catalyst membranes, which are potentially valuable for the continuous flow of catalytic reactions, e.g., the hydrogenation of p-nitrophenol. This study suggested that their porous structure and active Au nanoparticle catalyst allowed fast and mass catalytic functions by simple filtration without washing or catalyst recovery steps. We found no significant damage to the hybrid membrane during the reactions with a few liters; thus, we expect strong bindings of the Au nanoparticles on the surface of the porous LDH.

Amidoxime-functionalized aerogels for efficient adsorption of low-concentration metal pollutants

The treatment methods for heavy metal contaminants at low-concentrations (<10 mg/L) are attracting extensive attention due to the difficulty of degrading and the tendency of causing serious environmental hazards. As a result of the strong chelating ability to various metals, amidoxime structure is applicable in the adsorption of metal ions. Herein, it has been successfully synthesized amidoxime-functionalized acrylamide/amidoxime-chitosan (AM/AO-CS) aerogels as efficient adsorbents for low-concentration metal ions in aqueous solutions. The porous characteristics of chitosan carrier and abundant amidoxime groups make AM/AO-CS aerogels environmentally friendly and well-performing. AM/AO-CS aerogels displayed 97.4 % adsorption ratio of Cu2+ at a concentration of 10 mg/L. The adsorption isotherms of Cu2+ could be fit well by the Langmuir model. Moreover, AM/AO-CS aerogels adsorbed with Cu2+ were further applied as the catalysts in the hydrogenation of p-nitrophenol.

Ruthenium nickel bimetallic nanoparticles embedded in nitrogen-doped carbon mesoporous spheres as a superior catalyst for the hydrogenation of toxic nitroarenes

In this work, the ruthenium nickel bimetallic nanoparticles embedded in nitrogen-doped carbon mesoporous spheres (RuNi@ N-CMS) as a novel catalyst were designed and prepared. Hydrogenation of toxic p-nitrophenol into p-aminophenol was carried out in an aqueous medium using the prepared nanostructure. The as-synthesized RuNi@ N-CMS nanostructure displayed a better catalytic activity in comparison to both Ni@ N-CMS and Ru@ N-CMS nanostructures which can be ascribed to synergistic effects of ruthenium-nickel. In contrast to the nitrogen-doped catalyst, RuNi@CMS showed less activity, possibly because nitrogen acts as a secondary active site. The rate constant and TOF values were found to be 6.77 × 10-3 and 0.825 s−1 for hydrogenation of p-nitrophenol, respectively. Furthermore, RuNi@ N-CMS nanostructure was investigated in the reduction of nitroarene derivatives bearing electron-donating and electron-withdrawing groups. According to the kinetics study and Hammett plot of the reduction of nitroarenes, the cationic transition state is involved in the catalytic reaction. Most importantly, the catalyst could be recovered and reused after five consecutive runs without significantly deactivating.

Environmentally friendly molten salt synthesis of high-entropy AlCoCrFeNi alloy powder with high catalytic hydrogenation activity

A molten salt synthesis method was used to prepare high-entropy AlCoCrFeNi alloy powder with a high specific surface area of 67.5 m2/g, exhibiting remarkable catalytic activity in the hydrogenation of p-nitrophenol by NaBH4. The life cycle assessment of the proposed method indicated that AlCoCrFeNi production was associated with greenhouse gas emission of 125 kgCO2e/kg-product, whose main contributors were CaH2 and citric acid used during the precursor's reduction and formation, respectively. On the other hand, that for a previously reported dealloying method was 277 kg CO2e/kg-product. Thus, a minimum of 54% greenhouse gas emission reduction compared to the conventional dealloying method is achievable in the proposed molten salt method. The results indicated the possible environmentally friendly production of high-surface-area, high-entropy alloy powders suitable for industrial applications.

Thermodynamically and Kinetically Stabilized Pt Clusters Against Sintering on CeO2 Nanofibers Through Enclosing CeO2 Nanocubes.

Sintering is a major concern for the deactivation of supported metals catalysts, which is driven by the force of decreasing the total surface energy of the entire catalytic system. In this work, a double-confinement strategy is demonstrated to stabilize 2.6nm-Pt clusters against sintering on electrospun CeO2 nanofibers decorated by CeO2 nanocubes (m-CeO2 ). Thermodynamically, with the aid of CeO2 -nanocubes, the intrinsically irregular surface of polycrystalline CeO2 nanofibers becomes smooth, offering adjacent Pt clusters with decreased chemical potential differences on a relatively uniform surface. Kinetically, the Pt clusters are physically restricted on each facet of CeO2 nanocubes in a nanosized region. In situ high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) observation reveals that the Pt clusters can be stabilized up to 800°C even in a high density, which is far beyond their Tammann temperature, without observable size growth or migration. Such a sinter-resistant catalytic system is endowed with boosted catalytic activity toward both the hydrogenation of p-nitrophenol after being aged at 500°C and the sinter-promoting exothermic oxidation reactions (e.g., soot oxidation) at high temperatures over 700°C. This work offers new opportunities for exploring sinter-resistant nanocatalysts, starting from the rational design of whole catalytic system in terms of thermodynamic and kinetic aspects.

Towards multicomponent intermetallic nanoparticles as efficient and low-cost catalysts

Multicomponent intermetallic compounds consisting of different transition metal elements with high/medium entropy could be ideal candidates for catalysts in complex reactions. The possibility of electronic modification, isolation of active sites and structural stability in these compounds can result in excellent catalytic properties. Herein, we report a series of single-phase quinary antimonide intermetallic compounds with chemical composition of (NiCoFeCu)1-xSbx and hexagonal structure from bulk to nanoscale. The catalytic performance was examined in hydrogenation of p-nitrophenol to p-aminophenol using NaBH4. Structural and morphological characteristics of the samples before and after 10 runs of catalytic performance are described in detail. The kinetic rate constant for the best-synthesized sample (Nano40) is ten-fold compared to the bulk sample. All samples exhibit improved catalytic activity and extreme durability compared to the bimetallic nanoscale catalyst with the same structure. This significant enhance in catalytic activity of multicomponent structures makes them an attractive alternative to noble metal-based catalysts.

Polymeric multi-composites with a tailored nickel microenvironment as catalytic flow-through membrane reactors for efficient p-nitrophenol degradation

The catalytic degradation of environmental pollutants like p-nitrophenol is a promising approach for wastewater treatment. For this, it would be very beneficial to increase the catalytic efficiency of abundant non-noble metals and to fabricate materials that enable a continuous water treatment. In this work, a polymer-based membrane platform was established in a novel approach to immobilize nickel nanoparticles next to an adjustable multi-composite environment that improves the nickel activity for the catalytic hydrogenation of p-nitrophenol using borohydride. An optimized film casting and phase separation method with polyethersulfone as matrix polymer enabled the one-step fabrication of membranes with high loadings (53 wt%) of nickel nanoparticles, carbon nanoparticles and cationic ionomer, as well as high porosity (75%). The addition of carbon and ionomer optimized the nickel microenvironment in the porous membranes and doubled the p-nitrophenol turnover frequency in batch reaction. This is likely due to the utilization of in situ formed hydrogen by the carbon nanoparticles and the function of the cationic ionomer to bind p-nitrophenol and borohydride next to active sites. Combining these synergies between the functional additives with flow through the porous catalytic membrane reactors led to up to 10 times higher turnover frequencies and to an increase of reaction rate constants normalized to the nickel mass from 0.5 s−1 g−1 for dispersed nanoparticles to 140 s−1 g−1 for the best membrane. The multi-composite membranes also exhibit exceptional stability which enabled a continuous water treatment in flow-through for high p-nitrophenol concentration (50 mM or 7 g/L).

N-doped semi-graphitic C loaded with metallic Co: synthesis parameters and catalytic selective reduction of p-nitrophenol

The N-doped semi-graphitic C loaded with metallic Co (Co/CN) could catalyze highly selective hydrogenation of p-nitrophenol (100% conversion) to p-aminophenol (98.5% selectivity). The magnetically separable catalyst was reusable for 14 cycles.

Surface oxygen vacancies promoted Pt nanoparticles on celery-like CeO2 nanofibers for enhanced sinter-resistance and catalytic performance

Supported metal nanoparticles hold great promise for heterogeneous catalysis but are greatly persecuted by the poor thermal stability upon high temperatures. In this work, we facilely synthesized intriguing celery-like CeO2 nanofibers with high surface areas and hierarchical pores and channels by single-spinneret electrospinning. The nanofibers were explored as reliable support for polyvinylpyrrolidone (PVP)-stabilized Pt nanoparticles, followed by activation at 350 °C in N2 to eliminate PVP stabilizer and generate sufficient surface oxygen vacancies. Therefore, the resultant Pt@CeO2 was endowed with enhanced metal−support interaction and thereby promoted sinter-resistance. In this case, the Pt@CeO2 exhibited over six times higher activity after aging at 600 °C toward the hydrogenation of p-nitrophenol than that of PtPVP/CeO2. Moreover, the thermal-stable Pt@CeO2 significantly decreased the activation energy of soot oxidation from 178.0 kJ/mol to 109.4 kJ/mol, due to the abundant oxygen vacancies, as well as the promoted solid–solid contact by the interconnected and celery-like CeO2 nanofibers. After such a sinter-promoting exothermic reaction, the supported Pt nanoparticles maintained a small size of 5.78 nm. This approach provides a facile method to prepare noble metal catalysts with both high atom economy and sinterresistance.