Here we report a precise control of isolated single ruthenium site supported on nitrogen-doped porous carbon (Ru SAs/N–C) through a coordination-assisted strategy. This synthesis is based on the ...utilization of strong coordination between Ru3+ and the free amine groups (−NH2) at the skeleton of a metal–organic framework, which plays a critical role to access the atomically isolated dispersion of Ru sites. Without the assistance of the amino groups, the Ru precursor is prone to aggregation during the pyrolysis process, resulting in the formation of Ru clusters. The atomic dispersion of Ru on N-doped carbon can be verified by the spherical aberration correction electron microscopy and X-ray absorption fine structure measurements. Most importantly, this single Ru sites with single-mind N coordination can serve as a semihomogeneous catalyst to catalyze effectively chemoselective hydrogenation of functionalized quinolones.
The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms ...(Mo‐SAs) supported on N‐doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration‐corrected scanning transmission electron microscopy (AC‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo‐SAs anchored with one nitrogen atom and two carbon atoms (Mo1N1C2). Importantly, the Mo1N1C2 catalyst displayed much more excellent activity compared with Mo2C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo1N1C2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo‐based HER catalysts.
Single Mo atoms dispersed on N‐doped carbon was prepared as a catalyst. It showed high catalytic activity and stability for the hydrogen evolution reaction (HER), and its structure was characterized by electronic microscopy and XAFS measurements. The unique catalytic properties for HER were investigated by DFT calculations.
Iron (II) phthalocyanine (FePc) molecules were isolated in polyacrylonitrile (PAN) nanofibers by electrospinning to prevent the formation of dimers and oligomers. Carbamazepine (CBZ) and Rhodamine B ...(RhB) degradation was investigated during a Fenton-like process with FePc/PAN nanofibers. Classical quenching tests with isopropanol and electron paramagnetic resonance tests with 5,5-dimethyl-pyrroline-oxide as spin-trapping agent were performed to determine the formation of active species during hydrogen peroxide (H2O2) decomposition by FePc/PAN nanofibers. After eight recycles for CBZ degradation over the FePc/PAN nanofibers/H2O2 system, the removal ratios of CBZ remained at 99%. Seven by-products of RhB and twelve intermediates of CBZ were identified using ultra-performance liquid chromatography and high-resolution mass spectrometry. Pathways of CBZ and RhB degradation were proposed based on the identified intermediates. As the reaction proceeded, all CBZ and RhB aromatic nucleus intermediates decreased and were transformed to small acids, but also to potentially toxic epoxide-containing intermediates and acridine, because of the powerful oxidation ability of •OH in the catalytic system.
Display omitted
•FePc/PAN nanofiber catalysts were prepared by electrospinning method.•FePc molecules were isolated in PAN nanofibers to prevent the formation of dimers.•FePc/PAN nanofibers are efficient and stable for recalcitrant pollutant degradation.•The pathways of CBZ and RhB degradation were proposed.•Transformation products of CBZ and RhB were finally transformed to small acids.
Noble metals play a momentous role in heterogeneous catalysis but still face a huge challenge in selectivity control. Herein, we report isolating contiguous Pt atoms and forming Pt-Zn intermetallic ...nanoparticles as an effective strategy to optimize the selectivity of Pt catalysts. Contiguous Pt atoms are isolated into single atoms and Pt-Zn intermetallic nanoparticles are formed which are supported on hollow nitrogen-doped carbon nanotubes (PtZn/HNCNT), as confirmed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption spectrometry measurements. Interestingly, this PtZn/HNCNT catalyst promotes the hydrogenation of 4-nitrophenylacetylene to 4-aminophenylacetylene with a much higher conversion ( > 99%) and selectivity (99%) than the comparison samples with Pt isolated-single-atomic-sites (Pt/HNCNT) and Pt nanoparticles (Pt/CN). Further density functional theory (DFT) calculations disclose that the positive Zn atoms assist the adsorption of nitro group and Pt-Zn intermetallic nanoparticles facilitate the hydrogenation on nitro group kinetically.
Defects can greatly influence the properties of oxide materials; however, facile defect engineering of oxides at room temperature remains challenging. The generation of defects in oxides is difficult ...to control by conventional chemical reduction methods that usually require high temperatures and are time consuming. Here, we develop a facile room-temperature lithium reduction strategy to implant defects into a series of oxide nanoparticles including titanium dioxide (TiO
), zinc oxide (ZnO), tin dioxide (SnO
), and cerium dioxide (CeO
). Our lithium reduction strategy shows advantages including all-room-temperature processing, controllability, time efficiency, versatility and scalability. As a potential application, the photocatalytic hydrogen evolution performance of defective TiO
is examined. The hydrogen evolution rate increases up to 41.8 mmol g
h
under one solar light irradiation, which is ~3 times higher than that of the pristine nanoparticles. The strategy of tuning defect oxides used in this work may be beneficial for many other related applications.
Atomically monodispersed heterogeneous catalysts with uniform active sites and high atom utilization efficiency are ideal heterogeneous catalytic materials. Designing such type of catalysts, however, ...remains a formidable challenge. Herein, using a wet-chemical method, we successfully achieved a mesoporous graphitic carbon nitride (mpg-C
N
) supported dual-atom Pt
catalyst, which exhibited excellent catalytic performance for the highly selective hydrogenation of nitrobenzene to aniline. The conversion of ˃99% is significantly superior to the corresponding values of mpg-C
N
-supported single Pt atoms and ultra-small Pt nanoparticles (~2 nm). First-principles calculations revealed that the excellent and unique catalytic performance of the Pt
species originates from the facile H
dissociation induced by the diatomic characteristics of Pt and the easy desorption of the aniline product. The produced Pt
/mpg-C
N
samples are versatile and can be applied in catalyzing other important reactions, such as the selective hydrogenation of benzaldehyde and the epoxidation of styrene.
Abstract
Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single ...copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S
1
N
3
moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S
1
N
3
moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.
The construction of enzyme-inspired artificial catalysts with enzyme-like active sites and microenvironment remains a great challenge. Herein, we report a single-atomic-site Co catalyst supported by ...carbon doped boron nitride (BCN) with locally polarized B-N bonds (Co SAs/BCN) to simulate the reductive dehalogenases. Density functional theory analysis suggests that the BCN supports, featured with ionic characteristics, provide additional electric field effect compared with graphitic carbon or N-doped carbon (CN), which could facilitate the adsorption of polarized organochlorides. Consistent with the theoretical results, the Co SAs/BCN catalyst delivers a high activity with nearly complete dechlorination (~98%) at a potential of -0.9 V versus Ag/AgCl for chloramphenicol (CAP), showing that the rate constant (k) contributed by unit mass of metal (k/ratio) is 4 and 19 times more active than those of the Co SAs/CN and state-of-the-art Pd/C catalyst, respectively. We show that Co single atoms coupled with BCN host exhibit high stability and selectivity in CAP dechlorination and suppress the competing hydrogen evolution reaction, endowing the Co SAs/BCN as a candidate for sustainable conversion of organic chloride.
Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is ...reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration‐corrected high‐resolution transmission electron microscopy (HRTEM) and X‐ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4‐nitrostyrene to 4‐aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.
Taking the strain: Introducing Co atoms into a Ru catalyst compressed the Ru lattice strain, thus further affecting catalytic selectivity for hydrogenation of 4‐nitrostyrene to 4‐aminostyrene. Theoretical studies reveal that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group.
Cryptotanshinone is one of the major tanshinones isolated from the roots of the plant Salvia miltiorrhiza Bunge (Danshen). Danshen has been widely used in traditional Chinese medicine for treatment ...of a variety of diseases, including coronary artery disease, acute ischemic stroke, hyperlipidemia, chronic renal failure, chronic hepatitis, and Alzheimer's disease, showing no serious adverse effects. Recent studies have shown that cryptotanshinone not only possesses the potential for treatment and prevention of the above-mentioned diseases, but also is a potent anticancer agent. Here we briefly summarize the physical and chemical properties and the pharmacokinetic profiles of cryptotanshinone, and then comprehensively review its anticancer activities as well as the underlying mechanisms.
PDF
