Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 56
Filtrar
Mais filtros

Bases de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Nano Lett ; 24(3): 1015-1023, 2024 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-38215497

RESUMO

Ru-related catalysts have shown excellent performance for the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR); however, a deep understanding of Ru-active sites on a nanoscale heterogeneous support for hydrogen catalysis is still lacking. Herein, a click chemistry strategy is proposed to design Ru cluster-decorated nanometer RuxFe3-xO4 heterointerfaces (Ru/RuxFe3-xO4) as highly effective bifunctional hydrogen catalysts. It is found that introducing Ru into nanometric Fe3O4 species breaks the symmetry configuration and optimizes the active site in Ru/RuxFe3-xO4 for HER and HOR. As expected, the catalyst displays prominent alkaline HER and HOR performance with mass activity much higher than that of commercial Pt/C as well as robust stability during catalysis because of the strong interaction between the Ru cluster and the RuxFe3-xO4 support, and the optimized adsorption intermediate (Had and OHad). This work sheds light on a promsing approach to improving the electrocatalysis performance of catalysts by the breaking of atomic dimension symmetry.

2.
Small ; : e2402050, 2024 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-38801298

RESUMO

Electrocatalysis is a very attractive way to achieve a sustainable carbon cycle by converting CO2 into organic fuels and feedstocks. Therefore, it is crucial to design advanced electrocatalysts by understanding the reaction mechanism of electrochemical CO2 reduction reaction (eCO2RR) with multiple electron transfers. Among electrocatalysts, dual-atom catalysts (DACs) are promising candidates due to their distinct electronic structures and extremely high atomic utilization efficiency. Herein, the eCO2RR mechanism and the identification of intermediates using advanced characterization techniques, with a particular focus on regulating the critical intermediates are systematically summarized. Further, the insightful understanding of the functionality of DACs originates from the variable metrics of electronic structures including orbital structure, charge distribution, and electron spin state, which influences the active sites and critical intermediates in eCO2RR processes. Based on the intrinsic relationship between variable metrics and critical intermediates, the optimized strategies of DACs are summarized containing the participation of synergistic atoms, engineering of the atomic coordination environment, regulation of the diversity of central metal atoms, and modulation of metal-support interaction. Finally, the challenges and future opportunities of atomically dispersed catalysts for eCO2RR processes are discussed.

3.
Angew Chem Int Ed Engl ; 63(12): e202319618, 2024 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-38286759

RESUMO

Efficient dual-single-atom catalysts are crucial for enhancing atomic efficiency and promoting the commercialization of fuel cells, but addressing the sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline media and the facile dual-single-atom site generation remains formidable challenges. Here, we break the local symmetry of ultra-small ruthenium (Ru) nanoparticles by embedding cobalt (Co) single atoms, which results in the release of Ru single atoms from Ru nanoparticles on reduced graphene oxide (Co1 Ru1,n /rGO). In situ operando spectroscopy and theoretical calculations reveal that the oxygen-affine Co atom disrupts the symmetry of ultra-small Ru nanoparticles, resulting in parasitic Ru and Co dual-single-atom within Ru nanoparticles. The interaction between Ru single atoms and nanoparticles forms effective active centers. The parasitism of Co atoms modulates the adsorption of OH intermediates on Ru active sites, accelerating HOR kinetics through faster formation of *H2 O. As anticipated, Co1 Ru1,n /rGO exhibits ultrahigh mass activity (7.68 A mgRu -1 ) at 50 mV and exchange current density (0.68 mA cm-2 ), which are 6 and 7 times higher than those of Ru/rGO, respectively. Notably, it also displays exceptional durability surpassing that of commercial Pt catalysts. This investigation provides valuable insights into hybrid multi-single-atom and metal nanoparticle catalysis.

4.
Chem Rec ; 23(6): e202200278, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36807712

RESUMO

Lithium-Sulfur batteries (LSBs) have been considered as a promising candidate for the next generation of energy storage systems due to their high theoretical capacity. However, there are still lots of pending scientific and technological issues to be solved. Framework materials show great potential to address the above-mentioned issues due to the highly ordered distribution of pore sizes, effective catalytic activity, and periodically arranged aperture. In addition, good tunability gives framework materials unlimited possibilities to achieve satisfying performance for LSBs. In this review, the recent advances in pristine framework materials, their derivatives, and composites have been summarized. And a short conclusion and outlook regard to future prospects for guiding the development of framework materials and LSBs.


Assuntos
Fontes de Energia Elétrica , Lítio , Enxofre
5.
Chem Rec ; 23(6): e202200263, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36633461

RESUMO

As a porous and network materials consisting of metals and organic ligands, metal-organic frameworks (MOFs) have become one of excellent crystalline porous materials and play an important role in the era about materials science. Plasma, as a useful tool for stimulating efficient reactions under many conditions, and the plasma-assisted technology gets more attractions and endows MOFs more properties. Based on its feature, the research about the modifications and functionalities of MOFs have been developing a certain extent. This review contains a description of the methods for plasma-assisted modification and synthesis of MOFs, with specifically focusing on the plasma-assisted potential for modifications and functionalities of MOFs. The different applications of plasma-assisted MOFs were also presented.


Assuntos
Estruturas Metalorgânicas , Porosidade
6.
BMC Bioinformatics ; 23(1): 175, 2022 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-35549644

RESUMO

BACKGROUND: Lung cancer is one of the cancers with the highest mortality rate in China. With the rapid development of high-throughput sequencing technology and the research and application of deep learning methods in recent years, deep neural networks based on gene expression have become a hot research direction in lung cancer diagnosis in recent years, which provide an effective way of early diagnosis for lung cancer. Thus, building a deep neural network model is of great significance for the early diagnosis of lung cancer. However, the main challenges in mining gene expression datasets are the curse of dimensionality and imbalanced data. The existing methods proposed by some researchers can't address the problems of high-dimensionality and imbalanced data, because of the overwhelming number of variables measured (genes) versus the small number of samples, which result in poor performance in early diagnosis for lung cancer. METHOD: Given the disadvantages of gene expression data sets with small datasets, high-dimensionality and imbalanced data, this paper proposes a gene selection method based on KL divergence, which selects some genes with higher KL divergence as model features. Then build a deep neural network model using Focal Loss as loss function, at the same time, we use k-fold cross validation method to verify and select the best model, we set the value of k is five in this paper. RESULT: The deep learning model method based on KL divergence gene selection proposed in this paper has an AUC of 0.99 on the validation set. The generalization performance of model is high. CONCLUSION: The deep neural network model based on KL divergence gene selection proposed in this paper is proved to be an accurate and effective method for lung cancer prediction.


Assuntos
Aprendizado Profundo , Neoplasias Pulmonares , China , Expressão Gênica , Humanos , Neoplasias Pulmonares/genética , Redes Neurais de Computação
7.
Small ; 18(15): e2108097, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35233940

RESUMO

The density functional theory calculation results reveal that the adjacent defect concentration and electronic spin state can effectively activate the CoIII sites in the atomically thin nanosheets, facilitating the thermodynamic transformation of *O to *OOH, thus offering ultrahigh charge transfer properties and efficiently stabilizing the phase. This undoubtedly evidences that, for metal sulfides, the atom-scale cation/anion vacancy pair and surface electronic spin state can play a great role in enhancing the oxygen evolution reaction. Inspired by the theoretical prediction, interconnected selenium (Se) wired ultrathin Co3 S4 (Sex -Co3 S4 ) nanosheets with Co/S (Se) dual-vacancies (Se1.0 -Co3 S4 -VS/Se -VCo ) pairs are constructed by a simple approach. As an efficient sulfur host material, in an ultralow-concentration KOH solution (0.1 m), Se1.0 -Co3 S4 -VS/Se -VCo presents outstanding durability up to 165 h and a low overpotential of 289.5 mV at 10 mA cm-2 , which outperform the commercial Co3 S4 nanosheets (NSs) and RuO2 . Moreover, the turnover frequency of Se1.0 -Co3 S4 -VS/Se -VCo is 0.00965 s-1 at an overpotential of 0.39 V, which is 5.7 times that of Co3 S4 NSs, and 5.8 times that of commercial RuO2 . The finding offers a rational design strategy to create the multi-defect structure in catalysts toward high-efficiency water electrolysis.


Assuntos
Selênio , Água , Cátions , Oxirredução , Oxigênio
8.
Small ; 18(40): e2204155, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36050884

RESUMO

The coordination environment of Ru centers determines their catalytic performance, however, much less attention is focused on cluster-induced charge transfer in a Ru single-atom system. Herein, by density functional theory (DFT) calculations, a competitive coordination-pairing between Ru clusters (RuRu bond) and single-atoms (RuO bond) is revealed leading to the charge redistribution between Ru and O atoms in ZnFe2 O4 units which share more free electrons to participate in the hydrogen desorption process, optimizing the proton adsorption and hydrogen desorption. Thus, a clicking confinement strategy for building a competitive coordination-pairing between Ru clusters and single-atoms anchored on ZnFe2 Ox nanosheets over carbon via RuO ligand (Ru1, n -ZnFe2 Ox -C) is proposed. Benefiting from the optimized coordination effect and the electronic synergy between Ru clusters and single-atoms, such a catalyst demonstrates the excellent activity and excellent stability in alkaline and seawater media, which has exceptional hydrogen evolution reaction activity with overpotentials as low as 10.1 and 15.9 mV to reach the current density of 10 mA cm-2 in alkaline and seawater media, respectively, higher than that of commercial Pt/C catalysts as a benchmark. Furthermore, it owns remarkably outstanding mass activity, approximately 2 and 8 times higher than that of Pt catalysts in alkaline and seawater media, respectively.

9.
Biotechnol Bioeng ; 118(8): 2870-2885, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33930190

RESUMO

Host cell proteins (HCPs) are process-related impurities that may copurify with biopharmaceutical drug products. Within this class of impurities there are some that are more problematic. These problematic HCPs can be considered high-risk and can include those that are immunogenic, biologically active, or enzymatically active with the potential to degrade either product molecules or excipients used in formulation. Some have been shown to be difficult to remove by purification. Why should the biopharmaceutical industry worry about these high-risk HCPs? What approach could be taken to understand the origin of its copurification and address these high-risk HCPs? To answer these questions, the BioPhorum Development Group HCP Workstream initiated a collaboration among its 26-company team with the goal of industry alignment around high-risk HCPs. The information gathered through literature searches, company experiences, and surveys were used to compile a list of frequently seen problematic/high-risk HCPs. These high-risk HCPs were further classified based on their potential impact into different risk categories. A step-by-step recommendation is provided for establishing a comprehensive control strategy based on risk assessments for monitoring and/or eliminating the known impurity from the process that would be beneficial to the biopharmaceutical industry.


Assuntos
Produtos Biológicos/química , Indústria Farmacêutica , Produtos Biológicos/uso terapêutico , Medição de Risco
10.
Bull Math Biol ; 83(4): 39, 2021 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-33712983

RESUMO

Combination antiretroviral therapy (cART) has greatly increased life expectancy for human immunodeficiency virus-1 (HIV-1)-infected patients. Even given the remarkable success of cART, the virus persists in many different cells and tissues. The presence of viral reservoirs represents a major obstacle to HIV-1 eradication. These viral reservoirs contain latently infected long-lived cells. The "Shock and Kill" therapeutic strategy aims to reactivate latently infected cells by latency reversing agents (LRAs) and kill these reactivated cells by strategies involving the host immune system. The brain is a natural anatomical reservoir for HIV-1 infection. Brain macrophages, including microglia and perivascular macrophages, display productive HIV-1 infection. A mathematical model was used to analyze the dynamics of latently and productively infected brain macrophages during viral infection and this mathematical model enabled prediction of the effects of LRAs applied to the "Shock and Kill" strategy in the brain. The model was calibrated using reported data from simian immunodeficiency virus (SIV) studies. Our model produces the overarching observation that effective cART can suppress productively infected brain macrophages but leaves a residual latent viral reservoir in brain macrophages. In addition, our model demonstrates that there exists a parameter regime wherein the "Shock and Kill" strategy can be safe and effective for SIV infection in the brain. The results indicate that the "Shock and Kill" strategy can restrict brain viral RNA burden associated with severe neuroinflammation and can lead to the eradication of the latent reservoir of brain macrophages.


Assuntos
Encéfalo , Infecções por HIV , Modelos Biológicos , Síndrome de Imunodeficiência Adquirida dos Símios , Animais , Antivirais/uso terapêutico , Encéfalo/virologia , Infecções por HIV/tratamento farmacológico , Infecções por HIV/prevenção & controle , HIV-1 , Humanos , Síndrome de Imunodeficiência Adquirida dos Símios/tratamento farmacológico , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia
11.
Physica D ; 422: 132903, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33782628

RESUMO

The state of an infectious disease can represent the degree of infectivity of infected individuals, or susceptibility of susceptible individuals, or immunity of recovered individuals, or a combination of these measures. When the disease progression is long such as for HIV, individuals often experience switches among different states. We derive an epidemic model in which infected individuals have a discrete set of states of infectivity and can switch among different states. The model also incorporates a general incidence form in which new infections are distributed among different disease states. We discuss the importance of the transmission-transfer network for infectious diseases. Under the assumption that the transmission-transfer network is strongly connected, we establish that the basic reproduction number R 0 is a sharp threshold parameter: if R 0 ≤ 1 , the disease-free equilibrium is globally asymptotically stable and the disease always dies out; if R 0 > 1 , the disease-free equilibrium is unstable, the system is uniformly persistent and initial outbreaks lead to persistent disease infection. For a restricted class of incidence functions, we prove that there is a unique endemic equilibrium and it is globally asymptotically stable when R 0 > 1 . Furthermore, we discuss the impact of different state structures on R 0 , on the distribution of the disease states at the unique endemic equilibrium, and on disease control and preventions. Implications to the COVID-19 pandemic are also discussed.

12.
Gen Comp Endocrinol ; 277: 141-147, 2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30951727

RESUMO

The beneficial effects of dietary fiber on the reproductive performance and welfare of sows have been discussed broadly, but few researches examined the causal changes and the association of gut microbiota and the steroid hormones, the main regulators of reproductive function. To shed light on this, thirty-six Meishan sows were allocated into 2.5% crude fiber (CF) group and 7.5% CF group respectively for an entire farrowing interval. On the 90th day of gestation, the saliva and fresh stool of sows were individually collected in the morning (06:00-07:00) for steroid hormones, short-chain fatty acids (SCFAs) and microbiome analysis. In addition, the parameter of pregnant behavioral and farrowing performance was recorded and evaluated. We observed that, as compared with the 2.5% CF treatment, 7.5% CF significantly increased the litter size (p = 0.01), reduced the stereotypic behaviors including sham chewing, rolling tongue and licking ground (p = 0.02, 0.04, 0.01) at later gestation stage, but increased lying time (p = 0.00). In coincide with this, 7.5% CF diet increased the salivary progesterone (p = 0.00), fecal estradiol and progesterone (p = 0.01, 0.02) level, fecal water and SCFAs content (p = 0.02, 0.03), decreased the salivary and fecal cortisol (p = 0.01, 0.00) level. Further, 7.5% CF diet increased the fecal microbiota richness (ACE, p = 0.04; Chao, p = 0.07) and diversity (Shannon, p = 0.01; Simpson, p = 0.04), the proportion of genus Ruminococcus, Butyrivibrio, Lactobacillus and Fibrobacter (p = 0.02, 0.05, 0.04, 0.00), whereas reduced the proportion of genus Clostridium, Streptococcus, Bacteroides and Escherichia-Shigella (p = 0.00, 0.00, 0.04, 0.04). These results indicate that, fibrous diet can regulate the steroid hormones secretion and modulate the gut with more cellulose-degrading and probiotic bacterium, but less opportunistic pathogens, and this may contribute to the improvement of reproductive performance and welfare in sows.


Assuntos
Fibras na Dieta , Fezes/microbiologia , Hormônios/metabolismo , Microbiota , Suínos/microbiologia , Ração Animal , Animais , Comportamento Animal , Biodiversidade , Ácidos Graxos/metabolismo , Feminino , Filogenia , Gravidez , Saliva/metabolismo , Água
13.
J Am Chem Soc ; 140(8): 2731-2734, 2018 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-29415541

RESUMO

The construction of highly efficient and stable Pt-free catalysts for electrochemical hydrogen generation is highly desirable. Herein, we demonstrate the first metal-phosphides-metal system consisting of Ru, Ni2P, and Ni, which forms unique multiheterogeneous Ni@Ni2P-Ru nanorods. Interestingly, a Ru modulation effects that promotes the desorption of H2 to achieve a moderate hydrogen adsorption energy (ΔGH), and enables the formation of Ni@Ni2P nanorods via Ru-Ni coordination to enhance the conductivity was discovered. Due to its optimal ΔGH, improved conductivity and rod-like morphology, this catalyst shows superior electrocatalytic HER performances in both acidic and alkaline conditions, which are superior to those of some recently reported phosphides and close to that of commercial 20% Pt/C. Such a design strategy is not limited to Ni2P and Ru but also may be extended to other similar phosphides and noble metals, providing a new promising approach and an alternative to Pt catalysts for electrocatalytic applications.

14.
Analyst ; 143(13): 2997-3000, 2018 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-29872773

RESUMO

New S-doped yttrium oxide ultrathin nanosheets (NSs) were synthesized which had good electrochemiluminescence (ECL) properties. Through combining these NSs with small molecule linked DNA as the substrate, a novel ECL biosensor was constructed for the detection of protein biomarkers with an acceptable performance.


Assuntos
Anticorpos/análise , Técnicas Biossensoriais , Medições Luminescentes , Nanoestruturas , Ítrio , DNA , Digoxigenina , Humanos
15.
Ecotoxicol Environ Saf ; 162: 365-375, 2018 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-30007186

RESUMO

Blooms of Aureococcus anophagefferens, referred to as brown tides are responsible for massive mortalities and recruitment failure of some bivalves. However, the molecular mechanisms underlying the toxicity remain elusive despite its biological significance, and the information currently available on the molecular effects is still insufficient. In this study, to evaluate the toxicity and associated mechanism of A. anophagefferens on bivalves, we analyzed the protein expression profiles in digestive glands of the A. anophagefferens-exposed Perna viridis by using iTRAQ. A total of 3138 proteins were identified in the digestive glands of A. anophagefferens-exposed P. viridis based on iTRAQ. Amongst, a repertoire of 236 proteins involved in cell, cell part, catalytic activity, metabolic process, biological regulation, immune system process, and response to stimulus were found to be differentially expressed. Functional analysis of the differentially expressed proteins demonstrated that innate immune system of P. viridis was activated, and some proteins associated with stress response and lipid metabolism were induced after exposure to A. anophagefferens. Additionally, MDA content, SOD activity and GSH-Px activity was increased significantly in the digestive gland of A. anophagefferens-exposed P. viridis. Taken together, our results indicated that the A. anophagefferens could induce oxidative stress, activate complement system and alter fat acid metabolism of P. viridis.


Assuntos
Proliferação Nociva de Algas , Perna (Organismo)/metabolismo , Estramenópilas/química , Animais , Exposição Ambiental , Imunidade Inata , Modelos Biológicos , Estresse Oxidativo , Perna (Organismo)/imunologia , Perna (Organismo)/fisiologia , Proteômica
16.
Chemistry ; 23(72): 18203-18207, 2017 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-28741317

RESUMO

Freestanding metal nanoclusters can tune, precisely and effectively, the Gibbs free energy (ΔGH ) of atomic hydrogen on the surface of materials. This enables the enhancement of hydrogen evolution activity. In this paper, we report a study of freestanding Pd-Ru distorted icosahedral clusters (ico-clusters) with less than 600 atoms by using a simple one-pot synthesis method. This Pd-Ru ico-cluster can be used as an efficient electrocatalyst for the hydrogen evolution reaction (HER) in acidic water, which is a promising alternative to Pt. The experimental and theoretical results suggest that the face-centered cubic (fcc) freestanding Pd-Ru distorted ico-clusters with less than 600 atoms ensure increased active edges and distorted defect sites, which reduce the coordination number for the atoms on the catalyst surface. Furthermore, Ru is a more effective hydrogen dissociation source, whereas Pd has a better hydrogen storage function. Pd-Ru can tune the ΔGH of atomic hydrogen adsorbed on a catalyst and reach an optimal equilibrium state that improves the HER performance. Our studies represent a robust approach towards the development of freestanding Pd-Ru distorted ico-clusters and advanced catalysts with non-Pt content for HER and many other heterogeneous reactions.

17.
J Am Chem Soc ; 138(4): 1154-7, 2016 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-26785672

RESUMO

The research of highly active electrochemiluminescence (ECL) materials with low toxicity and good solubility remains a substantial challenge. In this work, we present a synthesis method to prepare soluble wurtzite (WZ) ZnSe nanocrystals (NCs), which exhibit good ECL properties. Using high-angle annular-dark-field imaging together with electron hologram methods, we observe that the WZ ZnSe NCs exhibit an unusual symmetry-breaking phenomenon, where the translational symmetry of the polarized Zn-Se bond is broken. The formation of a symmetry-breaking region leads to an accumulation of charge. The good ECL response originates from the increased efficiency of electron-hole recombination by the excess charge redistribution in WZ ZnSe NCs. This study of the relationship between ECL behavior and the architecture of NCs suggests that careful control over the NC structures of semiconductors can tailor their charge distribution via symmetry breaking, which opens new avenues for the design of novel classes of agents for optoelectronic applications.

18.
Anal Biochem ; 509: 142-145, 2016 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-27377969

RESUMO

N-glyco-occupancy and afucoslyation level are two important quality attributes associated with N-glycosylation of therapeutic monoclonal antibodies (mAbs). We report here a fast mass spectrometry-based workflow for quantification of N-glycan site-occupancy and afucoslyation level of mAbs with improved throughput, precision, sensitivity and robustness. This method uses the deglycosylation after the first GlcNAc and inter-chain reduction of the mAbs, followed by liquid chromatography/mass spectrometry (LC-MS) analysis. The entire process can be completed within one hour, which provides a rapid quantitation of N-glyco-occupancy and afucosylation to support high-throughput cell line selection and process development for mAb biopharmaceuticals.


Assuntos
Acetilglucosamina/química , Anticorpos Monoclonais Murinos/química , Fucose/química , Espectrometria de Massas/métodos , Glicosilação
19.
Bull Environ Contam Toxicol ; 96(4): 540-3, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26920698

RESUMO

A series of gramine modified montmorillonites (gramine-MMTs) were prepared and characterized by thermogravimetric analysis, X-ray diffraction and zeta potential measurements. These modified clays with various amounts of gramine all exhibited higher removal efficiencies of both Chattonella marina and Alexandrium tamarense than did natural clay. With the augmentation of gramine content in the modified clays, the removal efficiency increased. The 24 h LC50 values of gramine-MMT with 12.68 % of gramine on C. marina and A. tamarense were 9.16 and 10.21 mg L(-1), respectively. These data suggest gramine-MMT might be a promising material to remediate harmful algal blooms.


Assuntos
Alcaloides/química , Bentonita/química , Dinoflagellida/efeitos dos fármacos , Recuperação e Remediação Ambiental/métodos , Proliferação Nociva de Algas/efeitos dos fármacos , Silicatos de Alumínio/química , China , Argila , Alcaloides Indólicos , Tamanho da Partícula , Propriedades de Superfície , Termogravimetria , Difração de Raios X
20.
J Am Chem Soc ; 137(8): 2820-3, 2015 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-25626352

RESUMO

The synthesis of highly active oxygen reduction reaction (ORR) catalysts with good durability and low cost is highly desirable but still remains a significant challenge. In this work, we present the synthesis of five-fold twinned Pd2NiAg nanocrystals (NCs) with a Ni-terminal surface which exhibit excellent electrocatalytic performance for ORR in alkaline media, even better than the performance of the commercial Pt/C catalyst. Using high-angle annular-dark-field imaging together with density functional theory calculations, it is found that the surfaces of the five-fold twinned Pd2NiAg NCs exhibit an unusual valence electron density. The maximum catalytic activity originates from the increased availability of surface Ni sites in five-fold twinned Pd2NiAg NCs and the features of twinned structural defects. This study provides an explanation of the enhanced ORR from the special structure of this novel material, which opens up new avenues for the design of novel classes of electrocatalysts for fuel cells and metal-air batteries.


Assuntos
Nanopartículas Metálicas/química , Níquel/química , Oxigênio/química , Paládio/química , Prata/química , Catálise , Eletroquímica , Modelos Moleculares , Conformação Molecular , Oxirredução , Propriedades de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA