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Research Article Issue
Unraveling the advantages of Pd/CeO2 single-atom catalysts in the NO + CO reaction by model catalysts
Nano Research 2023, 16 (7): 8882-8892
Published: 14 April 2023
Downloads:59

Selective catalytic reduction of NO by CO is challenging in environmental catalysis but attractive owing to the advantage of simultaneous elimination of NO and CO. Here, model catalysts consisting of Pd nanoparticles (NPs) and single-atom Pd supported on a CeO2 (111) film grown on Cu (111) (denoted as Pd NPs/CeO2 and Pd1/CeO2, respectively) were successfully prepared and characterized by synchrotron radiation photoemission spectroscopy (SRPES) and infrared reflection absorption spectroscopy (IRAS). The NO + CO adsorption/reaction on the Pd1/CeO2 and Pd NPs/CeO2 catalysts were carefully investigated using SRPES, temperature-programmed desorption (TPD), and IRAS. It is found that the reaction products on both model catalysts are in good agreement with those on real catalysts, demonstrating the good reliability of using these model catalysts to study the reaction mechanism of the NO + CO reaction. On the Pd NPs/CeO2 surface, N2 is formed by the combination of atomic N coming from the dissociation of NO on Pd NPs at higher temperatures. N2O formation occurs probably via chemisorbed NO combined with atomic N on the surface. While on the single-atom Pd1/CeO2 surface, no N2O is detected. The 100% N2 selectivity may stem from the formation of O-N-N-O* intermediate on the surface. Through this study, direct experimental evidence for the reaction mechanisms of the NO + CO reaction is provided, which supports the previous density functional theory (DFT) calculations.

Research Article Issue
Porous γ-Fe2O3 nanoparticle decorated with atomically dispersed platinum: Study on atomic site structural change and gas sensor activity evolution
Nano Research 2021, 14 (5): 1435-1442
Published: 15 November 2020
Downloads:44

Decorating semi-conducting metal oxide with noble metal has been recognized as a viable approach to improve the sensitivity of gas sensor. However, conventional method which relys on noble metal nanoparticles is confronted with drawback of significantly increased cost. To maximize the atom efficiency and reduce the cost for practical industrial application, designing sensor material with noble metal isolated single atom sites (ISAS) doping is a desired option. Here, we report an atomically dispersed platinum on one-dimensional arranged porous γ-Fe2O3 nanoparticle composites as highly efficient ethanol gas sensor. The optimized sample (Pt1-Fe2O3-ox) exhibited a high response (Ra/Rg =102.4) and good selectivity to ethanol gas. It is demonstrated only the Pt single atom sites with high valance can effectively promote the adsorption capacity to ethanol and consequently enhance the sensitivity of sensing process by changing the electrical structure of Fe2O3 support. This work indicates the single atom sites could play a vital role in improving the performance of conventional metal oxides gas sensors and pave way for the exploration of ISAS-enhanced gas sensor for other volatile organic compounds (VOCs).

Research Article Issue
Controlling N-doping type in carbon to boost single-atom site Cu catalyzed transfer hydrogenation of quinoline
Nano Research 2020, 13 (11): 3082-3087
Published: 20 July 2020
Downloads:35

Single-atom site (SA) catalysts on N-doped carbon (CN) materials exhibit prominent performance for their active sites being M-Nx. Due to the commonly random doping behaviors of N species in these CN, it is a tough issue to finely regulate their doping types and clarify their effect on the catalytic property of such catalysts. Herein, we report that the N-doping type in CN can be dominated as pyrrolic-N and pyridinic-N respectively through compounding with different metal oxides. It is found that the proportion of distinct doped N species in CN depends on the acidity and basicity of compounded metal oxide host. Owing to the coordination by pyrrolic-N, the SA Cu catalyst displays an enhanced activity (two-fold) for transfer hydrogenation of quinoline to access the valuable molecule tetrahydroquinoline with a good selectivity (99%) under mild conditions. The higher electron density of SA Cu species induced by the predominate pyrrolic-N coordination benefits the hydrogen transfer process and reduces the energy barrier of the hydrogenation pathway, which accounts for the improved catalytic effeciency.

Research Article Issue
Metal-organic frameworks-derived nitrogen-doped carbon supported nanostructured PtNi catalyst for enhanced hydrosilylation of 1-octene
Nano Research 2019, 12 (10): 2584-2588
Published: 08 August 2019
Downloads:19

Here, we successfully developed nanostructured PtNi particles supported on nitrogen-doped carbon (NC), which were obtained by carbonization of metal-organic frameworks under different temperatures, forming the nano-PtNi/NC-600, nano-PtNi/NC-800, nano-PtNi/NC-900 and nano-PtNi/NC-1000 catalysts. For hydrosilylation of 1-octene, we found that the nano-PtNi/NC-1000 catalyst exhibits higher activity for anti-Markovnikov hydrosilylation of 1-octene than those of nano-PtNi/NC-600, nano-PtNi/NC-800, nano-PtNi/NC-900 catalysts. Experiments have verified that benefiting from obvious charge transfer from nano-PtNi particles to NC support carbonized at 1, 000 ℃, the nano-PtNi/NC-1000 catalyst achieved almost complete conversion and produce exclusive adduct for anti-Markovnikov hydrosilylation of 1-octene. Importantly, the nano-PtNi/NC-1000 catalyst exhibited good reusability for the hydrosilylation reaction. This work provides a new path to optimize electronic structure of catalysts by support modification to enhance electron transfer between metal active species and supports for highly catalytic performance.

Research Article Issue
Convenient fabrication of BiOBr ultrathin nanosheets with rich oxygen vacancies for photocatalytic selective oxidation of secondary amines
Nano Research 2019, 12 (7): 1625-1630
Published: 22 April 2019
Downloads:30

Photocatalytic oxidation has been widely employed in organic synthesis, by virtue of the green, mild and simple reaction conditions as well as high selectivity. Introducing oxygen vacancies (OVs) with proper concentrations into the photocatalysts has been proven as an effective strategy to boost the catalytic performances. However, the currently used treatment method under high temperature at reducing atmosphere inevitably introduces a large number of OVs at the interior of the catalyst and serving as the recombination centers of carriers. To address this issue, here we develop a facile solvothermal process to prepare ultrathin BiOBr nanosheets with rich surface OVs. This method effectively decreases the bulk of the material and the ratio of interior OVs, rendering most of the OVs exposed on the surfaces which act as exposed catalytic sites and enhance the separation of carriers, therefore significantly elevates the photocatalytic performances. For the photo-oxidation reaction of secondary amines, under the conditions of visible light, ambient temperature and atmosphere, the BiOBr nanosheets featuring rich surface OVs deliver a doubled conversion compared to those with low OV concentrations, and a high selectivity of 99%, a high stability as the performance shows no reduction after 5 times of circular reaction.

Research Article Issue
A general synthetic strategy to monolayer graphene
Nano Research 2018, 11 (6): 3088-3095
Published: 22 May 2018
Downloads:22

The emergence and establishment of new techniques for material fabrication are of fundamental importance in the development of materials science. Thus, we herein report a general synthetic strategy for the preparation of monolayer graphene. This novel synthetic method is based on the direct solid-state pyrolytic conversion of a sodium carboxylate, such as sodium gluconate or sodium citrate, into monolayer graphene in the presence of Na2CO3. In addition, gram-scale quantities of the graphene product can be readily prepared in several minutes. Analysis using Raman spectroscopy and atomic force microscopy clearly demonstrates that the pyrolytic graphene is composed of a monolayer with an average thickness of ~0.50 nm. Thus, the present pyrolytic conversion can overcome the issue of the low monolayer contents (i.e., 1 wt.%–12 wt.%) obtained using exfoliation methods in addition to the low yields of chemical vapor deposition methods. We expect that this novel technique may be suitable for application in the preparation of monolayer graphene materials for batteries, supercapacitors, catalysts, and sensors.

Research Article Issue
Controlled one-pot synthesis of RuCu nanocages and Cu@Ru nanocrystals for the regioselective hydrogenation of quinoline
Nano Research 2016, 9 (9): 2632-2640
Published: 17 June 2016
Downloads:28

RuCu nanocages and core–shell Cu@Ru nanocrystals with ultrathin Ru shells were first synthesized by a one-pot modified galvanic replacement reaction. The construction of bimetallic nanocrystals with fully exposed precious atoms and a high surface area effectively realizes the concept of high atom-efficiency. Compared with the monometallic Ru/C catalyst, both the RuCu nanocages and Cu@Ru core–shell catalysts supported on commercial carbon show superior catalytic performance for the regioselective hydrogenation of quinoline toward 1, 2, 3, 4-tetrahydroquinoline. RuCu nanocages exhibit the highest activity, achieving up to 99.6% conversion of quinoline and 100% selectivity toward 1, 2, 3, 4-tetrahydroquinoline.

Research Article Issue
Free-standing palladium-nickel alloy wavy nanosheets
Nano Research 2016, 9 (8): 2244-2250
Published: 01 June 2016
Downloads:16

Two-dimensional nanomaterials (2DNMs) have attracted increasing attention due to their unique properties and promising applications. Unlike 2DNMs with lamellar structures, metal ultrathin 2DNMs are difficult to synthesize and stabilize because they tend to form close-packed crystal structures. Most reported cases consist of monometallic and heterogeneous nanostructures. The synthesis of metal alloy 2DNMs has been rarely reported. Here, we report the synthesis of PdNi alloy wavy nanosheets (WNSs) using an enhanced CO-confinement strategy. This strategy is also suitable to the synthesis of other Pd-based alloy WNSs such as PdCu, PdFe, and even a trimetallic PdFeNi.

Research Article Issue
Pd-dispersed CuS hetero-nanoplates for selective hydrogenation of phenylacetylene
Nano Research 2016, 9 (4): 1209-1219
Published: 16 March 2016
Downloads:20

We have exploited a new and distinctive combination method that "disperses" elemental Pd into CuS nanoplates. Pd was successfully dispersed by means of the concomitant transformation of CuS into an amorphous sulfide, which formed an intimate metal–sulfide contact via cation exchange and underwent a subsequent reduction. A series of such Pd-dispersed CuS hetero-nanoplates were synthesized with tailored proportions and compositions. By efficient utilization of noble metal atoms and stable anchored active sites, the optimal catalytic performance for the semihydrogenation of phenylacetylene, a probe reaction, was achieved with high selectivity, activity, and stability. We believe that the synthetic strategy described in our study is a feasible means of developing effective metal–sulfide catalysts for organic reactions.

Research Article Issue
Phase-transfer interface promoted corrosion from PtNi10 nanoctahedra to Pt4Ni nanoframes
Nano Research 2015, 8 (1): 140-155
Published: 07 November 2014
Downloads:16

A novel two-phase approach towards the corrosion of PtNi10 nanoctahedra has been developed. In this strategy, the active component of Ni in oil-soluble PtNi10 nanoctahedra which resided in the upper toluene phase, suffered from etching and was then transferred into a lower aqueous phase with coordination by ethylenediaminetetraacetate (EDTA). Due to the existence of the phase-transfer interface promoted by EDTA, the corrosion reaction proceeded at an accelerated rate under the mild conditions. Specifically, the resultant products of octahedral Pt4Ni nanoframes were successfully fabricated for the first time, and PtNi4 porous octahedra could be obtained when the dosage of EDTA-2Na was reduced. After a systematic study of this two-phase system, a "synergetic corrosion" mechanism is proposed to account for the formation of octahedral Pt4Ni nanoframes, involving contributions from many species (i.e., O2, H2O, H+, OAm, and EDTA4-). As a result of the fascinating three-dimensional geometry of Pt4Ni nanoframes and PtNi4 porous octahedra, both of the corroded nanocrystals showed superior activity over the pristine PtNi10 nanoctahedra for ethanol electrooxidation in alkaline media and hydrogenation of nitrobenzene.

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