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The deposition of preformed nanocluster beams onto suitable supports represents a new paradigm for the precise preparation of heterogeneous catalysts. The performance of the new materials must be validated in model catalytic reactions. It is shown that gold/copper (Au/Cu) nanoalloy clusters (nanoparticles) of variable composition, created by sputte...
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Gold (Au) nanoparticles supported on certain platforms display highly efficient activity on nitroaromatics reduction. In this study, steam-activated carbon black (SCB) was used as a platform to fabricate Au/SCB catalysts via a green and simple method for 4-nitrophenol (4-NP) reduction. The obtained Au/SCB catalysts exhibit efficient catalytic perfo...
The present investigation deals with the importance of interaction and position of the nitro group in the adsorptive removal of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP) and phenol by demineralized kraft lignin activated carbon (DKLAAC). The adsorption of phenol and NPs on DKLAAC was found to follow the order 2-NP > 4-NP > phenol. In this study, b...
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Citations
... 17 Using this method, in this study, we investigate the formation process of Pd-based bimetallic nanoparticles synthesized by co-sputtering. It is a feature of the co-sputtering that can control the composition by changing the deposition rate of metals, and it has been used to form bimetallic nanoparticles on a solid surface 18,19 and in a liquid polymer. 20 Pd-based bimetallic nanoparticles are known to exhibit efficient catalytic properties, 21,22 for example, Pd-shell/Pt-core nanoparticles show enhanced electro-catalytic activity, 23,24 and it is applicable to fuel cells. ...
The formation process of Pd-based bimetallic nanoparticles synthesized by co-sputtering is investigated by performing in situ morphological observation using resistive spectroscopy. The segregation of the metal with lower surface energy on the nanoparticle surface is observed, and it is found that the formation process of the alloy nanoparticles tends to be similar to that of the nanoparticles composed of the core metal even when the atomic fraction of the shell metal is higher than that of the core metal. The co-sputtering process is simulated by the molecular dynamics analysis, and the observed formation process is theoretically confirmed.
... To quantify the reaction rates within the 30 min period, the apparent reaction rate, K app , which could be used to compare substance reactivity, is calculated (Cai et al., 2018). As shown in Fig. 4d, K app is 0.02, 0.06, 0.10, and 0.23 min − 1 for CDW-0, CDW-1, CDW-2, and CDW-3, respectively. ...
The Fenton-like reaction is a promising organic wastewater treatment reaction among advanced oxidation processes (AOP), which has emerged to replace the conventional Fenton reaction. Recycled construction and demolition waste (CDW), which is porous and rich in iron, manganese, and magnesium, can be reused as a Fenton-like catalyst. This study proposes an AOP wastewater treatment strategy using recycled porous CDW mixed with hydrogen peroxide (H2O2) to decompose methylene blue (MB) wastewater. According to the apparent first-order rate (Kapp) of 10 ppm MB adsorption, CDW-3, having the highest specific surface area, also has the highest Kapp of 0.23 min-1 g-1. The optimized conditions recommended by the Taguchi method include a 0.3 g mL-1 CDW-3 concentration, a 0.254 g mL-1 H2O2 concentration, and 10 ppm MB, resulting in an about 2.01 min-1Kapp value. In addition, MB concentration is observed as the most influential factor for Kapp, which decreases with increasing MB concentration and is about 0.62 min-1 at 1000 ppm MB. Repeating the Fenton-like reaction five times at 100 p.m. MB using the same CDW-3, the Kapp is about 0.64 min-1, which is 86% of the initial run. The synergistic effect index (ξ) is defined to quantify the level of interaction between CDW and H2O2, which produces free radicals during the Fenton-like process. The ξ of CDW-3 is about 2.16. Overall, it is demonstrated that CDW is a promising catalyst for Fenton-like reactions, and the synergistic effect index (ξ) can be used as a reference index to evaluate the catalytic generation of free radicals between the catalyst and H2O2.
... Thus, the synthesis of bi-and polymetallic nanoparticles is one of the most relevant areas of research in modern chemistry and materials science [1]. Nanoalloys can be produced using a variety of media, such as cluster beams and colloidal solutions, as well as immobilization on surfaces, inside pores, or even in carbon nanotubes [2][3][4][5]. Methods of metal reduction from precursor compounds at low temperatures [6,7] play an increasing role due to their relative simplicity, low cost, and the high quality of the final product. ...
Natural diamond crystals with a highly porous surface were used as substrates for synthesizing single-phase bimetallic Pt–Co nanoparticles at temperatures of 500 °C and 800 °C. The metal nanoparticles inside the pores were determined to take the form of single-phase Pt0.50Co0.50 solid solutions with different degrees of superstructure ordering. A detailed characterization of both nanoalloys revealed a tetragonal symmetry with a space group, P4/mmm. For the sample obtained at 500 °C, the lattice parameters were a = 2.673(2), c = 3.735(3) Å, and c/a = 1.397(1); for the samples obtained at 800 °C, the parameters were—a = 2.688(2), c = 3.697(3) Å, and c/a = 1.375(1). Within the experimental parameters, no significant chemical interaction of the diamond with the Pt–Co particles was identified. The results demonstrate a strong anchoring effect of the metallic material within the etching pores. The successful synthesis of bimetallic Pt–Co particles embedded inside the caverns can facilitate a study of their magnetic properties. The presence of Pt–Co in specific diamond compositions can also be used for marking diamond crystals as a means for their subtle identification, as well as confirming the possibility of capturing significant amounts of metal along with diamonds during their dissolution in the deep Earth.
... (b) Catalyst agglomerated after reaction. References [14,15,[27][28][29][30][31][32][33][34][35][36][37][38][39] are cited in the supplementary materials. ...
Single-atom catalysts (SACs) have been synthesized using a variety of methods in recent years, and they have shown excellent catalytic activities. However, metal atoms show a high tendency to agglomerate in liquid media, making the single atom synthesis more difficult in liquid media. The synthesis of such metal single-atom catalysts that do not have strong ligand coordination is rarely reported in the literature. Herein, we report the facile synthesis of monodispersed Au atoms (Au1) through the reduction in HAuCl4 in 15-crown-5. The complete reduction in HAuCl4 was confirmed through UV-Vis spectroscopy. In addition, the Au was found in a zero valence state after reduction, which was confirmed through XPS and XANES results. Moreover, the dispersion of Au was confirmed as a single atom (Au1) through transmission electron microscopy and spherical aberration electron microscopy. The possible structure of this catalyst was proposed by matching the EXAFS results with the structure of Au1@15-crown-5 as -(OC2H4O)-AuCl2H2. The Au1@15-crown-5 showed high activity (TOF as high as 22,075) in the reduction in nitrophenol and nitroaniline to aminophenol and phenylenediamine by sodium borohydride. Because of the monodispersion of Au atoms, its performance is much better than noble nanoparticles and non-precious metal catalysts.
... TEM isn't an in-situ method and usually can't yield high enough resolution for sub-2 nm clusters. The spectroscopic techniques, such as single-crystal X-ray diffraction [9], extended X-ray absorption fine structure (EXAFS) [10], energy dispersive spectroscopy (EDS) [11], and nuclear magnetic resonance spectroscopy (NMR) [12] usually require tedious and time-consuming single crystal growth techniques and expensive instruments. ...
... Then the restraint was removed and the POM passed the protein nanopore as driven by the electric field, which blocked the ionic current ( Figure 3A, S7&S8). The ionic current was calculated using the g_flux utility, 11 and the average values in every 50 ns (to reduce the statistical error) were shown in the figures. ...
It is important and challenging to analyze nanocluster structure with atomic precision. Herein, α-hemolysin nanopore was used to identify nanoclusters at the single molecule level by providing 2D dwell time-current blockage spectra and translocation event frequency which sensitively depended on their structures. Nanoclusters such as Anderson, Keggin, Dawson, and a few lacunary Dawson polyoxometalates with very similar structures, even with only a two-atom difference, could be discriminated. This nanopore device could simultaneously measure multiple nanoclusters in a mixture qualitatively and quantitatively. Furthermore, molecular dynamics (MD) simulations provided microscopic understandings of the nanocluster translocation dynamics and yielded 2D dwell time-current blockage spectra in close agreement with experiments. The nanopore platform provides a novel powerful tool for nanocluster characterization.
... [11] Therefore, there are many ways to detect and degrade these compounds, such as electrochemical sensor, [12] photocatalysis, [13] microbial catalysis and metal catalysis. [14][15][16][17] Of notable significance, metal catalysis is widely studied because of its characteristics of simple operation, fast reaction speed and no special reaction device required. [18] Many semiconductors, including Cu 2 O, Cu 2À x S, TiO 2 , and CdSe, can be used as catalysts to effectively degrade organic pollutants in wastewater. ...
... As shown in Table 2, compared with other materials, Cu 2 O/Au has better catalytic performance and can degrade p-nitrophenol in a short time. [17,38,39] In order to test the universality of the materials, we extended to other nitro aromatic compounds under the same experimental conditions. [40] The experimental results are shown in Table S1. ...
The conversion of nitroaromatics to aminobenzene plays an important role in the synthesis of medicines or fine chemicals. In this work, we successfully prepared Cu2O/Au nanocubes with different Au content for the reduction of 4‐nitrophenol. With the increase of gold precursor concentration or reaction time, the density of Au nanoparticles (NPs)on Cu2O surface increases, which results in the stronger electron transfer between Au and Cu2O, and thus the better synergistic catalytic performance of Cu2O/Au nanoparticles toward 4‐Nitrophenol (4‐NP). In this work, we found the Au component in the nanoparticles played an important role in charge redistribution and transfer, as well as the adsorption and reduction of 4‐NP. Therefore, the degradation performance of Cu2O/Au composite is better than that of pure Cu2O, and the degradation rate of 4‐NP can reach almost 90 % in 10 min, therefore providing a new idea for the rational design of effective nanocatalysts.
... A new perspective on size-effect-supported Au catalysts for CO oxidation is presented; different size-dependent reaction pathways contribute to catalytic activity. Gold clusters are easier to aggregate than various other particles because of their higher surface energy [21][22][23]. Experimental and theoretical studies have been carried out to understand the high catalytic activity of gold clusters and particles. Gold clusters exhibit an excellent ability to catalyze a variety of industrially and environmentally important chemical reactions, such as propylene oxidation [24][25][26], the hydrodeoxygenation of guaiacol [27], the catalytic reduction of 4-nitrophenol [28] and graphene oxide [29], and the 1,2-aminoarylation of alkenes with external amines [30]. ...
Significant progress has been made in understanding the reactivity and catalytic activity of gas-phase and loaded gold clusters for CO oxidation. However, little research has focused on mixed silicon/gold clusters (SiAun) for CO oxidation. In the present work, we performed density function theory (DFT) calculations for a SiAun (n = 1–5) cluster at the CAM-B3LYP/aug-cc-pVDZ-PP level and investigated the effects on the reactivity and catalytic activity of the SiAun cluster for CO oxidation. The calculated results show that the effect is very low for the activation barriers for the formation of OOCO intermediates on SiAu clusters, SiAu3 clusters, and SiAu5 clusters in the catalytic oxidation of CO and the activation energy barriers for the formation of OCO intermediates on OSiAu3, OSiAu4, and OSiAu5. Our calculations show that, compared with the conventional small Au cluster, the incorporation of Si enhances the catalytic performance towards CO oxidation.
... In this method, the unique extra nuclear valence electron characteristics of its own metal is used to form a large number of M-H (M is noble metal nanoparticles) active species, which can significantly accelerate the reaction process of dye degradation. At present, the commonly used precious metals in many industries J Mater Sci (2023) 58:1026-1043 include gold [4], copper [5], silver [6], palladium [7], platinum [8], and so on. ...
As a typical two-dimensional MXene material with abundant oxygen-containing functional groups, Ti3C2 could be used as an excellent carrier for noble metal nanoparticles to effectively avoid its agglomeration. However, Ti3C2 was easily oxidized and deteriorated when stored in a conventional environment, so polydopamine (PDA) was used to modify Ti3C2 to promote uniform loading of noble metal nanoparticles. Based on this, with Ti3AlC2 as the raw material and PDA as the modifier, in situ growth of gold nanoparticles was carried out using chloroauric acid trihydrate as the precursor, and the target nanocomposite catalyst (Au@P-Ti3C2) was then obtained. A sequence of characterizations were employed to analyze chemical structure of the resulting catalyst. The catalytic degradation performances of Au@P-Ti3C2 toward amaranth, methylene blue, chrome black T, and Congo red were systematically investigated, and the results showed that catalytic degradation percentage of Au@P-Ti3C2 for the above dyes could reach 100%. The pseudo-first-order kinetic model could be used to simulate the catalytic reaction process well, and catalytic reaction rate constants of Au@P-Ti3C2(2) for the four pollutants were 0.0411 s⁻¹, 0.0721 s⁻¹, 0.0273 s⁻¹, and 0.0105 s⁻¹, respectively. After 10 cycles of repeated catalysis, catalytic degradation percentage of the composite catalyst toward the four dyes could still remain above 89%. Therefore, this novel, green, and simple method to synthesize Ti3C2-based composite catalyst might provide extremely valuable application prospect for MXene-based catalyst in the field of harmless treatment of industrial dyes.
Graphical Abstract
... A large-scale conversion of benzene to cyclohexane and the production of L-DOPA, a drug used to treat Alzheimer's disease, are instructive examples of the reaction. Over more than 100 years numerous catalysts, both homogeneous and heterogeneous, have been adjusted to the hydrogenation though usually most of them contain a noble-metal core (Au [6], Pt [7], Rh [8], Ru [9], Ir [10], or Pd [11]) as an active site for the reaction. As indicated by a patent landscape analysis, the process of developing new catalysts has accelerated over the last 25 years [12]. ...
... Anal. Calcd for C 6 ...
Aim. To share our experience when working with the Pd-catalyzed hydrogenation and discuss reactions occurred contrary to our expectations, as well as express our vision of the causes for such an unusual reactivity.
Results and discussion. Catalysis is a key technology and among the central themes of both petrochemical and fine chemical industries. Although extremely useful and reliable, it can sometimes astonish researchers. The paper discusses 17 intriguing cases of the catalytic hydrogenation and hydrogenolysis reactions from our practice in the High-pressure Synthesis Laboratory (Enamine Ltd.). All examples presented are characterized by peculiar performance of commercially sourced heterogeneous palladium-containing catalysts (Pd/C or Pd(OH)2). Thus, some cases were characterized by reduced activity of the catalyst (or even its complete loss), meaning that reaction conditions found before to be suitable for reduction appeared to be “broken”, and we had to search for a new, often harsher reaction setup. Curiously, it is a matter of classical Pd-catalyzed hydrogenations of N+–O– and C=C fragments. Apparently, these results indicate the heterogeneity of commercially available catalysts and are related to their fine internal structure, in particular the surface morphology. Another interesting issue the article deals with is chemoselectivity of the catalytic hydrogenation. Sometimes some reactions led to astonishing results going across theoretical views and expectations. Saturation of benzene rings instead of (or accompanying) debenzylation, breaking of the common order of hydrogenation for compounds containing several aromatic parts with different resonance energies, irreproducible experiment, obtaining of different products under the same conditions, uncommon results of Pd-catalyzed reactions is the list of interesting results, which we observed and discussed in the article. Analyzing the information available in the literature and considering all the results gathered we tend to believe that the presence of impurities of noble metals (Rh, Ru, Pt) in the catalysts used to be a possible reason for these strange findings. The study supports the general idea that commercial palladium catalysts differ in efficiency, resulting in significant differences in selectivity, reaction time, and yields. Elucidating the regularities behind such empirical results is undoubtedly an interesting area of research in the field of catalysis.
Experimental part. All starting compounds exposed to hydrogenation were synthesized in Enamine Ltd. and had purity of not less than 95 %. The palladium-containing catalysts used in the experiment were purchased from 6 commercial sources within 2011 – 2022. The structure and purity of the compounds synthesized were characterized by 1H NMR spectroscopy, liquid chromatography coupled with the mass spectrometry method, elemental analysis. Chromatographic experiments revealed the purity of all compounds obtained being not less than 95 %.
Conclusions. In the paper we have summarized our experience with the Pd-catalyzed hydrogenation and presented cases of unusual reactivity or unexpected outcomes of the reactions encountered in our practice. In general, complications we faced were of three types: (1) irreproducibility of the procedures most likely as the result of a changeable activity of the catalysts; (2) chemoselectivity issues when two or multireducible functional groups were present in the substrate; (3) undesirable Pd-catalyzed defunctionalization reactions. In turn, these complications led to increase in production costs, loss of time and resources. Therefore, because of this variability in the efficiency of Pd catalysts, far more efforts are required to find out the key differences between commercial sources of Pd catalysts, as well as to create protocols clearly defining the catalytic activity of each batch of the catalyst allowing to identify high-quality catalysts immediately prior to the use without wasting precious time and synthetic materials.
... This is supported by the calculated adsorption energies of 4-nitrophenol to the corresponding Au, Ni or Ni/Au model surface (Fig. 8a-c). The adsorption energy of 4-nitrophenol on Ni/Au was calculated to be − 0.33 eV compared with 0.082 eV for Au (Fig. 8a) and − 1.22 eV for Ni (Fig. 8b), confirming that Ni exhibits the strongest adsorption capacity towards 4-nitrophenol, whereas 4-nitrophenol is hardly attracted to Au (Cai et al., 2018b;Wu et al., 2020). However, catalytic performance is also affected by desorption of the product. ...
... However, catalytic performance is also affected by desorption of the product. As shown in Fig. 8e-f, the adsorption energy of 4-aminophenol on Ni/Au (-0.21 eV) is larger than that on Au (-0.085 eV), but significantly smaller than that on Ni (-0.64 eV), indicating that 4-aminophenol exhibits a stronger interaction with Ni than Au (Cai et al., 2018b;Wu et al., 2020). Thus, although Ni was beneficial for the adsorption of 4-nitrophenol, it retains the 4-aminophenol to a greater extent resulting in decreased catalytic performance. ...
Porous monolithic microreactors show great promise in catalytic applications, but are usually based on non-renewable materials. Herein, we demonstrate a Ni/Au nanoparticle-decorated carbonized wood (Ni/Au-CW) monolithic membrane microreactor for the efficient reduction of 4-nitrophenol. The hierarchical porous wood structure supports uniformly distributed heterobimetallic Ni/Au nanoparticles. As a consequence of these two factors, both mass diffusion and electron transfer are enhanced, resulting in a superior reduction efficiency of 99.5% as the liquor flows through the optimised Ni/Au-CW membrane. The reaction mechanism was investigated by electron paramagnetic resonance spectroscopy and density functional theory calculations. The proposed attraction-repulsion mechanism facilitated by the bimetallic nanoparticles has been ascribed to the different electronegativities of Ni and Au. The Ni/Au-CW membrane exhibits excellent catalytic performance and could be applicable to other catalytic transformations.
