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1.
Angew Chem Int Ed Engl ; : e202406262, 2024 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-38787604

RESUMO

Single-atom catalysts (SACs) have recently become highly attractive for selective hydrogenation reactions owing to their remarkably high selectivity. However, compared to their nanoparticle counterparts, atomically dispersed metal atoms in SACs often show inferior activity and are prone to aggregate under reaction conditions. Here, by theoretical calculations, we show that tuning the local electronic structures of metal anchor sites on g-C3N4 by doping B atoms (BCN) with relatively lower electronegativity allows achieving zero-valence Pd SACs with reinforced metal-support orbital hybridizations for high stability and upshifted Pd 4d orbitals for high activity in H2 activation. The precise synthesis of Pd SACs on BCN supports with varied B contents substantiated the theoretical prediction. A zero-valence Pd1/BCN SAC was achieved on a BCN support with a relatively low B content. It exhibited much higher stability in a H2 reducing environment, and more strikingly, a hydrogenation activity, approximately 10 and 34 times greater than those high-valence Pd1/g-C3N4 and Pd1/BCN with a high B content, respectively.

2.
Angew Chem Int Ed Engl ; : e202404398, 2024 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-38698730

RESUMO

Catalyst deactivation by sintering and coking is a long-standing issue in metal-catalyzed harsh high-temperature hydrocarbon reactions. Ultrathin oxide coatings of metal nanocatalysts have recently appeared attractive to address this issue, while the porosity of the overlayer is difficult to control to preserve the accessibility of embedded metal nanoparticles, thus often leading to a large decrease in activity. Here, we report that a nanometer-thick alumina coating of MgAl2O4-supported metal catalysts followed by high-temperature reduction can transform a nonporous amorphous alumina overlayer into a porous Mg1‒xAl2Oy crystalline spinel structure with a pore size of 2‒3 nm and weakened acidity. The high porosity stems from the restrained Mg migration from the MgAl2O4 support to the alumina overlayer through solid-state reactions at high temperatures. The resulting Ni/MgAl2O4 and Pt/MgAl2O4 catalysts with a porous crystalline Mg1‒xAl2Oy overlayer achieved remarkably high stability while preserving much higher activity than the corresponding alumina-coated Ni and Pt catalysts on MgO and Al2O3 supports in the reactions of dry reforming of methane and propane dehydrogenation, respectively.

3.
Front Microbiol ; 14: 1266254, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37869677

RESUMO

Introduction: Persistent human papillomavirus infection is an important factor in the development of cervical cancer, which is usually a long process evolving from the development of squamous intraepithelial lesions (SIL), also referred to as cervical intraepithelial neoplasia (CIN). Local treatment of advanced squamous intraepithelial lesions, also regarded as High-Grade Squamous Intraepithelial Lesion, may be effective in preventing cancer. Objective: To promptly identify high-risk patients with a tendency to recurrence. Methods: We retrospectively analyzed the clinical data of 300 patients with high-grade squamous intraepithelial lesions of the cervix admitted to the Second Affiliated Hospital of Dalian Medical University from 2019 to 2020 to investigate the relationship between recurrence of cervical lesions and postoperative regression of HPV infection, as well as other related risk factors. Results: We found that the HPV-negative rates were 81.81, 85.71, and 90.91% at 6, 12, and 24 months, respectively, and the average lesion recurrence rate was 8.16%, with a median time to recurrence of 14 months in patients undergoing CKC for HSIL. The risk of cervical squamous intraepithelial lesions was highest in patients with HPV16. Patients over 61 years of age had the lowest postoperative HPV-negative rate. The conversion rate was significantly lower in patients with multiple HPV genotypes than in those with single HPV infection (p < 0.05). The probability of recurrence was higher in patients with the same HPV infection genotype before and after surgery than in patients with different infection genotypes before and after surgery (p < 0.05). Conclusion: Combined with the literature review, we believe that patients aged ≥50 years, with ≥3 pregnancies and births, a history of smoking, and consistent genotypes of preoperative and postoperative HPV infection in cervical conization have more HPV re-infection or persistent infection, and that these factors may be high-risk factors for lesion recurrence. For patients with possible potential high-risk factors, we need to carry out individualized follow-up and focused management, take timely and effective management measures, optimize the treatment plan, reduce the recurrence rate, prevent HSIL and cervical cancer, improve the quality of patient's survival, and improve the prognosis.

4.
ACS Appl Mater Interfaces ; 15(39): 46292-46299, 2023 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-37733926

RESUMO

The pyroelectric effect is used in a wide range of applications such as infrared (IR) detection and thermal energy harvesting, which require the pyroelectric materials to simultaneously have a high pyroelectric coefficient and a low dielectric constant for high figures of merit. However, in conventional proper ferroelectrics, the positive correlation between the pyroelectric coefficient and the dielectric constant imposes an insurmountable challenge in upgrading the figures of merit. Here, we explored superior pyroelectricity in [(CH3)4N][FeCl4] (TMA-FC) and [(CH3)4N][FeCl3Br] (TMA-FCB) molecular ferroelectric plastic crystals, which could decouple this positive correlation due to the nature of improper polarization behavior. Therefore, TMA-FC and TMA-FCB derive a high pyroelectric coefficient and a low dielectric constant simultaneously, yielding record-high figures of merit around room temperature. Furthermore, the favorable plasticity enables ferroelectric crystals to attach surfaces with different shapes for device design and integration. More interestingly, the molecular ferroelectrics could be softened and reshaped at elevated temperatures without decay in pyroelectricity, making them recyclable for cost savings and e-waste reduction. Combined with the facile fabrication process, the findings of this work would open avenues for employing molecular ferroelectric plastic crystals in the manufacture of high-performance pyroelectric devices.

5.
Front Microbiol ; 14: 1220522, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37577444

RESUMO

Cervical carcinoma is the fourth female malignant tumor in the world, and the persistent infection of high-risk human papillomavirus (HPV) is recognized as the most common cause. This article studies the correlation between multiple HPV infections and the occurrence, development, and prognosis of cervical cancer in order to provide more references for clinical diagnosis and treatment. We conducted a retrospective analysis of the clinical data of 400 cervical carcinoma patients admitted to our hospital from 2015 to 2023. The collected patient data include age, HPV infection status, tumor size and morphology, local infiltration depth, diagnostic staging, surgical approach, vascular cancer thrombus status, lymph node status, and postoperative HPV follow-up status. We use SPSS statistical software for data analysis. Our research shows that the high-risk age group for cervical carcinoma is concentrated between 41 and 60 years old, which is basically consistent with the age range of the high incidence of HPV infection. In the statistics for HPV infection types, ~67.7% of patients are single HPV-infected, 25.29% are double infected, and 7.00% are infected with three or more types of HPV. Among the multiple HPV infections, most of the patients are younger than 40 years old and older than 70 years old, with double infection accounting for the majority. The top five HPV subtypes with high detection rates belong to high-risk subtypes, which are the HPV16, 18, 58, 33, and 52 subtypes, respectively. There was no significant relationship between multiple HPV infections and cervical cancer stage, lesion size, pathological tissue type, tissue differentiation degree/vascular cancer thrombus, and lymph node metastasis, and there was no significant difference in the results between the groups. In summary, multiple types of HPV infection in the cervix are common. We found that multiple infections, mainly HPV16, are closely related to cervical cancer. For the HPV16, 18, 58, 33, and 52 subtypes of infection, especially for patients younger than 40 years old and older than 70 years old, priority should be given to prevention and treatment. The relationship between multiple HPV infections and the progression and prognosis of cervical carcinoma requires further research, which could better guide cancer prevention and treatment.

6.
Angew Chem Int Ed Engl ; 62(23): e202300110, 2023 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-37026370

RESUMO

Increasing selectivity without the expense of activity is desired but challenging in heterogeneous catalysis. By revealing the molecule saturation and adsorption sensitivity on overlayer thickness, strain, and coordination of Pd-based catalysts from first-principles calculations, we designed a stable Pd monolayer (ML) catalyst on a Ru terrace to boost both activity and selectivity of acetylene semihydrogenation. The least saturated molecule is most sensitive to the change in catalyst electronic and geometric properties. By simultaneously compressing the Pd ML and exposing the high coordination sites, the adsorption of more saturated ethylene is considerably weakened to facilitate the desorption for high selectivity. The even stronger weakening to the least saturated acetylene drives its hydrogenation such that it is more exothermic, thereby boosting the activity. Tailoring the molecule saturation and its sensitivity to structure and composition provides a tool for rational design of efficient catalysts.

7.
J Am Chem Soc ; 145(12): 6702-6709, 2023 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-36920448

RESUMO

Reactive metal-support interactions (RMSIs) induce the formation of bimetallic alloys and offer an effective way to tune the electronic and geometric properties of metal sites for advanced catalysis. However, RMSIs often require high-temperature reductions (>500 °C), which significantly limits the tuning of bimetallic compositional varieties. Here, we report that an atomically thick Ga2O3 coating of Pd nanoparticles enables the initiation of RMSIs at a much lower temperature of ∼250 °C. State-of-the-art microscopic and in situ spectroscopic studies disclose that low-temperature RMSIs initiate the formation of rarely reported Ga-rich PdGa alloy phases, distinct from the Pd2Ga phase formed in traditional Pd/Ga2O3 catalysts after high-temperature reduction. In the CO2 hydrogenation reaction, the Ga-rich alloy phases impressively boost the formation of methanol and dimethyl ether ∼5 times higher than that of Pd/Ga2O3. In situ infrared spectroscopy reveals that the Ga-rich phases greatly favor formate formation as well as its subsequent hydrogenation, thus leading to high productivity.

8.
Nat Commun ; 14(1): 530, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36725854

RESUMO

Core-shell bimetallic nanocatalysts have attracted long-standing attention in heterogeneous catalysis. Tailoring both the core size and shell thickness to the dedicated geometrical and electronic properties for high catalytic reactivity is important but challenging. Here, taking Au@Pd core-shell catalysts as an example, we disclose by theory that a large size of Au core with a two monolayer of Pd shell is vital to eliminate undesired lattice contractions and ligand destabilizations for optimum benzyl alcohol adsorption. A set of Au@Pd/SiO2 catalysts with various core sizes and shell thicknesses are precisely fabricated. In the benzyl alcohol oxidation reaction, we find that the activity increases monotonically with the core size but varies nonmontonically with the shell thickness, where a record-high activity is achieved on a Au@Pd catalyst with a large core size of 6.8 nm and a shell thickness of ~2-3 monolayers. These findings highlight the conjugated dual particle size effect in bimetallic catalysis.

9.
Angew Chem Int Ed Engl ; 62(8): e202218167, 2023 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-36573769

RESUMO

Tuning the coordination environments of metal single atoms (M1 ) in single-atom catalysts has shown large impacts on catalytic activity and stability but often barely on selectivity in thermocatalysis. Here, we report that simultaneously regulating both Rh1 atoms and ZrO2 support with alkali ions (e.g., Na) enables efficient switching of the reaction products from nearly 100 % CH4 to above 99 % CO in CO2 hydrogenation in a wide temperature range (240-440 °C) along with a record high activity of 9.4 molCO gRh -1 h-1 at 300 °C and long-term stability. In situ spectroscopic characterization and theoretical calculations unveil that alkali ions on ZrO2 change the surface intermediate from formate to carboxy species during CO2 activation, thus leading to exclusive CO formation. Meanwhile, alkali ions also reinforce the electronic Rh1 -support interactions, endowing the Rh1 atoms more electron deficient, which improves the stability against sintering and inhibits deep hydrogenation of CO to CH4 .

10.
Front Cell Infect Microbiol ; 12: 917009, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36310872

RESUMO

Gastric-type mucinous endocervical adenocarcinomas (GAS) are new variant types of cervical adenocarcinomas according to the 2014 World Health Organization (WHO) classification. GAS is a unique disease that can be differentiated from typical adenocarcinomas-it is less common and more aggressive and likely to have deep invasion and horizontal diffusion, invasion of the uterus and vagina, early distant metastases, and a lower 5-year survival rate compared to the usual-type cervical cancer. At present, initial treatment and postoperative adjuvant therapy are not conclusive, but early detection and early treatment are a consensus that can improve prognosis. Most of its occurrence has nothing to do with human papillomavirus (HPV) infection. Whether it is only negative for the subtypes that can be detected at present and whether it may be an unknown subtype of infection need to be further explored in the future. The clinical symptoms commonly include aqueous secretion, lower abdominal pain, and elevated serum carbohydrate antigen-19-9 (CA19-9) levels, which may be helpful for diagnosis. MRI and PET-CT can help to describe the characteristics of lesions and judge the state of the systemic metastasis. We believe that early detection and surgical treatment will give patients more benefits. Looking for potential gene and molecular changes and establishing biomarkers to identify molecular targets will be the key to early identification and target therapy.


Assuntos
Adenocarcinoma Mucinoso , Adenocarcinoma , Infecções por Papillomavirus , Neoplasias Gástricas , Neoplasias do Colo do Útero , Feminino , Humanos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Adenocarcinoma Mucinoso/diagnóstico por imagem , Neoplasias do Colo do Útero/diagnóstico , Adenocarcinoma/diagnóstico , Adenocarcinoma/patologia
11.
Front Cell Infect Microbiol ; 12: 916506, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35909972

RESUMO

Cervical SCNEC is a rare and highly malignant invasive tumor. The incidence is low, at less than 5% of all cervical cancers. Moreover, most patients with small cell carcinoma are interrelated with high risk HPV (more familiar HPV 18). Compared to squamous cell carcinoma or adenocarcinoma, patients of cevical SCNEC are more prone to lymph node invasion early, so the clinical manifestation is usually local or distant metastasis. We summarized the clinical features of 19 patients with cervical small cell carcinoma in the Second Affiliated Hospital of Dalian Medical University from 2012 to 2021, and retrospectively analyzed data from 1576 patients in 20 related studies and more than 50 pieces of literature in recent years by searching PubMed, Google schalor, Cochrane Library, Clinicalkey, and other databases. The collected patient data included age, clinical manifestation, TCT, HPV detection, the size and morphology of the tumor, local invasion depth, stage, lymph node status, initial treatment method, tumor-free survival, and so on. The positive rates of CGA, SYN, and CD56 in our cases were high, and NSE was a moderately sensitive index. P16 and Ki67 were the most sensitive, and all patients were positive. We found that multimodal treatment can indeed improve tumor-free survival (DFS), but the prognosis of patients is still very poor. For the early stages, our treatment principles refer to the guidelines of SGO, international gynecological cancer Cooperation (GCIG), and NCCN. We suggest a combination of surgery, radiotherapy, and chemotherapy. However, the general state of advanced patients is poor, whether they can tolerate the operation after neoadjuvant chemotherapy, whether the operation area can remain tumor-free, and whether this treatment will prolong the survival time of patients still need to be further discussed. In order to better prolong the tumor-free survival and prognosis of patients, we need to find gene changes suitable for targeted therapy, so as to complete the clinical application of these treatment methods. Further works are needed to explore more effective therapy for cervical SCNEC.


Assuntos
Carcinoma Neuroendócrino , Carcinoma de Células Pequenas , Infecções por Papillomavirus , Neoplasias do Colo do Útero , Carcinoma Neuroendócrino/patologia , Carcinoma Neuroendócrino/terapia , Carcinoma de Células Pequenas/patologia , Carcinoma de Células Pequenas/terapia , Colo do Útero , Feminino , Humanos , Metástase Linfática/patologia , Infecções por Papillomavirus/complicações , Estudos Retrospectivos , Neoplasias do Colo do Útero/terapia
12.
Angew Chem Int Ed Engl ; 61(41): e202211919, 2022 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-35981974

RESUMO

Regulation of the atom-atom interspaces of dual-atom catalysts is essential to optimize the dual-atom synergy to achieve high activity but remains challenging. Herein, we report an effective strategy to regulate the Pt1 -Ni1 interspace to achieve Pt1 Ni1 dimers and Pt1 +Ni1 heteronuclear dual-single-atom catalysts (HDSACs) by tailoring steric hindrance between metal precursors during synthesis. Spectroscopic characterization reveals obvious electron transfers in Pt1 Ni1 oxo dimers but not in Pt1 +Ni1 HDSAC. In the hydrolysis of ammonia borane (AB), the H2 formation rates show an inverse proportion to the Pt1 -Ni1 interspace. The rate of Pt1 Ni1 dimers is ≈13 and 2 times higher than those of Pt1 and Pt1 +Ni1 HDSAC, manifesting the interspace-dependent synergy. Theoretical calculations reveal that the bridging OH group in Pt1 Ni1 dimers promotes water dissociation, while Pt1 facilitates the cleavage of B-H bonds in AB, which boosts a bifunctional synergy to accelerate H2 production cooperatively.

13.
Angew Chem Int Ed Engl ; 61(23): e202202330, 2022 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-35322514

RESUMO

The active site of the industrial Cu/ZnO/Al2 O3 catalyst used in CO2 hydrogenation to methanol has been debated for decades. Grand challenges remain in the characterization of structure, composition, and chemical state, both microscopically and spectroscopically, and complete theoretical calculations are limited when it comes to describing the intrinsic activity of the catalyst over the diverse range of structures that emerge under realistic conditions. Here a series of inverse model catalysts of ZnO on copper hydroxide were prepared where the size of ZnO was precisely tuned from atomically dispersed species to nanoparticles using atomic layer deposition. ZnO decoration boosted methanol formation to a rate of 877 gMeOH kgcat -1 h-1 with ≈80 % selectivity at 493 K. High pressure in situ X-ray absorption spectroscopy demonstrated that the atomically dispersed ZnO species are prone to aggregate at oxygen-deficient ZnO ensembles instead of forming CuZn metal alloys. By modeling various potential active structures, density functional theory calculations and microkinetic simulations revealed that ZnO/Cu interfaces with oxygen vacancies, rather than stoichiometric interfaces, Cu and CuZn alloys were essential to catalytic activation.

14.
ACS Nano ; 16(3): 3744-3755, 2022 03 22.
Artigo em Inglês | MEDLINE | ID: mdl-35234032

RESUMO

Currently, various electronic devices make our life more and more safe, healthy, and comfortable, but at the same time, they produce a large amount of nondegradable and nonrecyclable electronic waste that threatens our environment. In this work, we explore an environmentally friendly and flexible mechanical sensor that is biodegradable and recyclable. The sensor consists of a bacterial cellulose (BC) hydrogel as the matrix and imidazolium perchlorate (ImClO4) molecular ferroelectric as the functional element, the hybrid of which possesses a high sensitivity of 4 mV kPa-1 and a wide operational range from 0.2 to 31.25 kPa, outperforming those of most devices based on conventional functional biomaterials. Moreover, the BC hydrogel can be fully degraded into glucose and oligosaccharides, while ImClO4 can be recyclable and reused for the same devices, leaving no environmentally hazardous electronic waste.


Assuntos
Celulose , Hidrogéis , Materiais Biocompatíveis , Eletrônica
15.
J Am Chem Soc ; 143(45): 18854-18858, 2021 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-34730347

RESUMO

Controlling the chemical environments of the active metal atom including both coordination number (CN) and local composition (LC) is vital to achieve active and stable single-atom catalysts (SACs), but remains challenging. Here we synthesized a series of supported Pt1 SACs by depositing Pt atoms onto the pretuned anchoring sites on nitrogen-doped carbon using atomic layer deposition. In hydrogenation of para-chloronitrobenzene, the Pt1 SAC with a higher CN about four but less pyridinic nitrogen (Npyri) content exhibits a remarkably high activity along with superior recyclability compared to those with lower CNs and more Npyri. Theoretical calculations reveal that the four-coordinated Pt1 atoms with about 1 eV lower formation energy are more resistant to agglomerations than the three-coordinated ones. Composition-wise decrease of the Pt-Npyri bond upshifts gradually the Pt-5d center, and minimal one Pt-Npyri bond features a high-lying Pt-5d state that largely facilitates H2 dissociation, boosting hydrogenation activity remarkably.

16.
ACS Appl Mater Interfaces ; 13(39): 47252-47261, 2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34546698

RESUMO

Understanding the dynamic process of interfacial charge transfer prior to chemisorption is crucial to the development of electrocatalysis. Recently, interfacial water has been highlighted in transferring protons through the electrode/electrolyte interface; however, the identification of the related structural configurations and their influences on the catalytic mechanism is largely complicated by the amorphous and mutable structure of the electrical double layer (EDL). To this end, sub-nanometric Pt electrocatalysts, potentially offering intriguing activity and featuring fully exposed atoms, are studied to uncover the elusive electrode/electrolyte interface via operando X-ray absorption spectroscopy during the hydrogen evolution reaction (HER). Our results show that the metallic Pt clusters derived from the reduction of sub-nanometric Pt clusters (SNM-Pt) exhibit excellent HER activity, with an only 18 mV overpotential at 10 mA/cm2 and one-magnitude-higher mass activity than commercial Pt/C. More importantly, a unique Pt-interfacial water configuration with a Pt (from Pt clusters)-O (from water) radial distance of approximately 2.5 Å is experimentally identified as the structural foundation for the interfacial proton transfer. Toward high overpotentials, the interfacial water that structurally evolves from "O-close" to "O-far" accelerates the proton transfer and is responsible for the improved reaction rate by increasing the hydrogen coverage.

17.
Front Plant Sci ; 12: 627311, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34305958

RESUMO

Green light, as part of the photosynthetically active radiation, has been proven to have high photosynthetic efficiency once absorbed by plant leaves and can regulate plant physiological activities. However, few studies have investigated the appropriate and efficient way of using the green light for plant production. Thus, the objective of this study was to investigate a moderate amount of green light, partially replacing red and blue light, for plant growth and development. In this experiment, four treatments were set up by adjusting the relative amount of green light as 0 (RB), 30 (G30), 60 (G60), and 90 (G90) µmol m-2 s-1, respectively, with a total photosynthetic photon flux density of 200 µmol m-2 s-1 and a fixed red-to-blue ratio of 4:1. Lettuce (Lactuca sativa cv. 'Tiberius') plant growth and morphology, stomatal characteristics, light absorptance and transmittance, photosynthetic characteristics, and nutritional quality were investigated. The results showed that: (1) shoot dry weight increased by 16.3 and 24.5% and leaf area increased by 11.9 and 16.2% under G30 and G60, respectively, compared with those under RB. Plant stem length increased linearly with increasing green-to-blue light ratio; (2) light transmittance of lettuce leaf under treatments employing green light was higher than that under RB, especially in the green region; (3) stomatal density increased, whereas stomatal aperture area decreased with the increase in the relative amount of green light; and (4) carbohydrate accumulation increased under G60 and G90. Soluble sugar contents under G60 and G90 increased by 39.4 and 19.4%, respectively. Nitrate contents under G30, G60, and G90 decreased by 26.2, 40.3, and 43.4%, respectively. The above results indicated that 15-30% green light replacing red and blue light effectively increased the yield and nutritional quality of lettuce plants.

18.
Adv Mater ; 33(35): e2008471, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34296473

RESUMO

Single-atom catalysts (SACs) represent a new frontier in heterogeneous catalysis due to their remarkable catalytic properties and maximized atomic utilization. However, single atoms often bond to the support with polarized electron density and thus exhibit a high valence state, limiting their catalytic scopes in many chemical transformations. Here, it is demonstrated that 2D black phosphorus (BP) acts as giant phosphorus (P) ligand to confine a high density of single atoms (e.g., Pd1 , Pt1 ) via atomic layer deposition. Unlike other 2D materials, BP with relatively low electronegativity and buckled structure favors the strong confinement of robust zero-valent palladium SACs in the vacancy site. Metallic Pd1 /BP SAC shows a highly selective semi-hydrogenation of phenylacetylene toward styrene, distinct from metallic Pd nanoparticles that facilitate the formation of fully hydrogenated products. Density functional theory calculations reveal that Pd atom forms covalent-like bonding with adjacent P atoms, wherein H atoms tend to adsorb, aiding the dissociative adsorption of H2 . Zero-valent Pd in the confined space favors a larger energy gain for the synthesis of partially hydrogenated product over the fully hydrogenated one. This work provides a new route toward the synthesis of zero-valent SACs on BP for organic transformations.

19.
Nat Nanotechnol ; 16(10): 1141-1149, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34312515

RESUMO

Atomically dispersed metal catalysts maximize atom efficiency and display unique catalytic properties compared with regular metal nanoparticles. However, achieving high reactivity while preserving high stability at appreciable loadings remains challenging. Here we solve the challenge by synergizing metal-support interactions and spatial confinement, which enables the fabrication of highly loaded atomic nickel (3.1 wt%) along with dense atomic copper grippers (8.1 wt%) on a graphitic carbon nitride support. For the semi-hydrogenation of acetylene in excess ethylene, the fabricated catalyst shows extraordinary catalytic performance in terms of activity, selectivity and stability-far superior to supported atomic nickel alone in the absence of a synergizing effect. Comprehensive characterization and theoretical calculations reveal that the active nickel site confined in two stable hydroxylated copper grippers dynamically changes by breaking the interfacial nickel-support bonds on reactant adsorption and making these bonds on product desorption. Such a dynamic effect confers high catalytic performance, providing an avenue to rationally design efficient, stable and highly loaded, yet atomically dispersed, catalysts.

20.
Angew Chem Int Ed Engl ; 60(35): 19324-19330, 2021 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-34184379

RESUMO

Semi-hydrogenation of acetylene to ethylene is an important process to purify ethylene streams in industry. However, among current approaches reported in the literature, high ethylene selectivity has been generally achieved at the expense of activity. Herein, we show that a Ga2 O3 coating of Ag@Pd core-shell bimetallic nanoparticle catalysts, allows improvement of the ethylene selectivity to a much greater extent than the coating of monometallic Pd nanoparticles, while preserving a remarkable intrinsic activity, approximately 50 times higher than the benchmark catalyst of Pd1 Ag single-atom alloys (SAAs). Importantly, the resulting catalyst also shows excellent long-term stability, by suppressing coke formation efficiently. Spectroscopic characterization reveals that weakened ethylene adsorption by bimetallic electronic synergy, and oxide site isolation are both essential for the high ethylene selectivity and high-coking resistance. H-D exchange measurements further show that the Ga2 O3 -coated Ag@Pd catalyst possesses a much higher activity of H2 activation than that of Pd1 Ag SAAs, thus boosting the hydrogenation activity at the same time.

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