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1.
Nat Chem ; 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32541950

RESUMO

Single-atom catalysts not only maximize metal atom efficiency, they also display properties that are considerably different to their more conventional nanoparticle equivalents, making them a promising family of materials to investigate. Herein we developed a general host-guest strategy to fabricate various metal single-atom catalysts on nitrogen-doped carbon (M1/CN, M = Pt, Ir, Pd, Ru, Mo, Ga, Cu, Ni, Mn). The iridium variant Ir1/CN electrocatalyses the formic acid oxidation reaction with a mass activity of 12.9 [Formula: see text] whereas an Ir/C nanoparticle catalyst is almost inert (~4.8 × 10-3 [Formula: see text]). The activity of Ir1/CN is also 16 and 19 times greater than those of Pd/C and Pt/C, respectively. Furthermore, Ir1/CN displays high tolerance to CO poisoning. First-principle density functional theory reveals that the properties of Ir1/CN stem from the spatial isolation of iridium sites and from the modified electronic structure of iridium with respect to a conventional nanoparticle catalyst.

2.
Chem Rev ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32242408

RESUMO

Manipulating metal atoms in a controllable way for the synthesis of materials with the desired structure and properties is the holy grail of chemical synthesis. The recent emergence of single atomic site catalysts (SASC) demonstrates that we are moving toward this goal. Owing to the maximum efficiency of atom-utilization and unique structures and properties, SASC have attracted extensive research attention and interest. The prerequisite for the scientific research and practical applications of SASC is to fabricate highly reactive and stable metal single atoms on appropriate supports. In this review, various synthetic strategies for the synthesis of SASC are summarized with concrete examples highlighting the key issues of the synthesis methods to stabilize single metal atoms on supports and to suppress their migration and agglomeration. Next, we discuss how synthesis conditions affect the structure and catalytic properties of SASC before ending this review by highlighting the prospects and challenges for the synthesis as well as further scientific researches and practical applications of SASC.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32282112

RESUMO

Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory-guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi-hydrogenation processes. Such Ni sites show not only preferential acetylene π-adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, including aberration-corrected high-resolution scanning transmission electron microscopy and X-ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni5 Ga3 intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi-atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation.

4.
Artigo em Inglês | MEDLINE | ID: mdl-32189435

RESUMO

The solar-driven photocatalytic reduction of CO2 (CO2 RR) into chemical fuels is a promising route to enrich energy supplies and mitigate CO2 emissions. However, low catalytic efficiency and poor selectivity, especially in a pure-water system, hinder the development of photocatalytic CO2 RR owing to the lack of effective catalysts. Herein, we report a novel atom-confinement and coordination (ACC) strategy to achieve the synthesis of rare-earth single erbium (Er) atoms supported on carbon nitride nanotubes (Er1 /CN-NT) with a tunable dispersion density of single atoms. Er1 /CN-NT is a highly efficient and robust photocatalyst that exhibits outstanding CO2 RR performance in a pure-water system. Experimental results and density functional theory calculations reveal the crucial role of single Er atoms in promoting photocatalytic CO2 RR.

5.
Angew Chem Int Ed Engl ; 59(3): 1295-1301, 2020 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-31654544

RESUMO

It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron-hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO2 support (Pt1 /def-TiO2 ). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO2 units to generate surface oxygen vacancies and form a Pt-O-Ti3+ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt-O-Ti3+ atomic interface effectively facilitates photogenerated electrons to transfer from Ti3+ defective sites to single Pt atoms, thereby enhancing the separation of electron-hole pairs. This unique structure makes Pt1 /def-TiO2 exhibit a record-level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h-1 , exceeding the Pt nanoparticle supported TiO2 catalyst by a factor of 591.

6.
Chem Rev ; 120(2): 623-682, 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31868347

RESUMO

The use of well-defined materials in heterogeneous catalysis will open up numerous new opportunities for the development of advanced catalysts to address the global challenges in energy and the environment. This review surveys the roles of nanoparticles and isolated single atom sites in catalytic reactions. In the second section, the effects of size, shape, and metal-support interactions are discussed for nanostructured catalysts. Case studies are summarized to illustrate the dynamics of structure evolution of well-defined nanoparticles under certain reaction conditions. In the third section, we review the syntheses and catalytic applications of isolated single atomic sites anchored on different types of supports. In the final part, we conclude by highlighting the challenges and opportunities of well-defined materials for catalyst development and gaining a fundamental understanding of their active sites.

7.
Stem Cell Res Ther ; 10(1): 389, 2019 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-31842983

RESUMO

OBJECTIVE: Neural tube defects (NTDs) are the most serious and common birth defects in the clinic. The SRY-related HMG box B1 (SoxB1) gene family has been implicated in different processes of early embryogenesis. Sox19b is a maternally expressed gene in the SoxB1 family that is found in the region of the presumptive central nervous system (CNS), but its role and mechanism in embryonic neural stem cells (NSCs) during neural tube development have not yet been explored. Considering that Sox19b is specific to bony fish, we intended to investigate the role and mechanism of Sox19b in neural tube development in zebrafish embryos. MATERIAL AND METHODS: Morpholino (MO) antisense oligonucleotides were used to construct a Sox19b loss-of-function zebrafish model. The phenotype and the expression of related genes were analysed by in situ hybridization and immunolabelling. Epigenetic modifications were detected by western blot and chromatin immunoprecipitation. RESULTS: In this study, we found that zebrafish embryos exhibited a reduced or even deleted forebrain phenotype after the expression of the Sox19b gene was inhibited. Moreover, we found for the first time that knockdown of Sox19b reduced the proliferation of NSCs; increased the transcription levels of Ngn1, Ascl1, HuC, Islet1, and cyclin-dependent kinase (CDK) inhibitors; and led to premature differentiation of NSCs. Finally, we found that knockdown of Sox19b decreased the levels of EZH2/H3K27me3 and decreased the level of H3K27me3 at the promoters of Ngn1 and ascl1a. CONCLUSION: Together, our data demonstrate that Sox19b plays an essential role in early NSC proliferation and differentiation through EZH2-mediated histone methylation in neural tube development. This study established the role of transcription factor Sox19b and epigenetic factor EZH2 regulatory network on NSC development, which provides new clues and theoretical guidance for the clinical treatment of neural tube defects.


Assuntos
Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Histonas/metabolismo , Células-Tronco Neurais/metabolismo , Tubo Neural/crescimento & desenvolvimento , Fatores de Transcrição SOX/metabolismo , Proteínas de Peixe-Zebra/metabolismo , Animais , Diferenciação Celular/fisiologia , Modelos Animais de Doenças , Técnicas de Silenciamento de Genes , Metilação , Células-Tronco Neurais/citologia , Tubo Neural/citologia , Tubo Neural/metabolismo , Prosencéfalo/embriologia , Prosencéfalo/metabolismo , Fatores de Transcrição SOX/biossíntese , Fatores de Transcrição SOX/genética , Peixe-Zebra , Proteínas de Peixe-Zebra/biossíntese , Proteínas de Peixe-Zebra/genética
8.
J Am Chem Soc ; 141(42): 16569-16573, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31588748

RESUMO

The electrocatalytic reduction reaction of CO2 (CO2RR) is a promising strategy to promote the global carbon balance and combat global climate change. Herein, exclusive Bi-N4 sites on porous carbon networks can be achieved through thermal decomposition of a bismuth-based metal-organic framework (Bi-MOF) and dicyandiamide (DCD) for CO2RR. Interestingly, in situ environmental transmission electron microscopy (ETEM) analysis not only directly shows the reduction from Bi-MOF into Bi nanoparticles (NPs) but also exhibits subsequent atomization of Bi NPs assisted by the NH3 released from the decomposition of DCD. Our catalyst exhibits high intrinsic CO2 reduction activity for CO conversion, with a high Faradaic efficiency (FECO up to 97%) and high turnover frequency of 5535 h-1 at a low overpotential of 0.39 V versus reversible hydrogen electrode. Further experiments and density functional theory results demonstrate that the single-atom Bi-N4 site is the dominating active center simultaneously for CO2 activation and the rapid formation of key intermediate COOH* with a low free energy barrier.

9.
Cell Death Dis ; 10(3): 211, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30824686

RESUMO

Offspring of mothers with hyperglycemia during pregnancy have a higher incidence of long-term neuropsychiatric disorders than offspring from a normal pregnancy, indicating that neocortical neurogenesis might be affected by maternal hyperglycemia. A paucity of study evaluating the effects of hyperglycemia on neocortical neurogenetic differentiation of neural stem cells, and the mechanism remains unclear. We sought to investigate the the roles and possible molecular mechanism of maternal hyperglycemia on neocortical neurogenetic differentiation of neural stem cells. We established a mouse model of a hyperglycemic pregnancy to study effects of intrauterine exposure to maternal hyperglycemia on neocortical neurogenesis. We observed morphological changes in the neocortex and detected the neurogenetic differentiation of neural stem cells in offspring affected by high glucose levels. We investigated the regulatory network between epigenetic modification and transcription factors in differentiated neural stem cells under hyperglycemic conditions. Maternal hyperglycemia disturbs neocortical lamination in some non-malformed offspring. Our results suggested that hyperglycemia altered the early-born neuron fate and the distribution of newborn neurons in deep layers by promoting the earlier differentiation of neural stem cells. Altered histone acetylation and its regulation on the transcription of proneural genes might be correlated to the disrupted differentiation of neural stem cells and altered distribution of newborn projection neurons in the neocortex. Our data raised the possibility that maternal hyperglycemia in pregnancy disturbs the laminar distribution of neocortical projection neurons in some non-malformed offspring via epigenetic regulation on neural stem cell differentiation and the birthdate of neocortical neurons.

10.
Cell Death Dis ; 10(3): 198, 2019 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-30814486

RESUMO

Cellular metabolism plays a crucial role in controlling the proliferation, differentiation, and quiescence of neural stem cells (NSCs). The metabolic transition from aerobic glycolysis to oxidative phosphorylation has been regarded as a hallmark of neuronal differentiation. Understanding what triggers metabolism reprogramming and how glucose metabolism directs NSC differentiation may provide new insight into the regenerative potential of the brain. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is an endogenous inhibitor of glycolysis and is highly expressed in mature neurons. However, its function in embryonic NSCs has not yet been explored. In this study, we aimed to investigate the precise roles of TIGAR in NSCs and the possible involvement of metabolic reprogramming in the TIGAR regulatory network. We observed that TIGAR is significantly increased during brain development as neural differentiation proceeds, especially at the peak of NSC differentiation (E14.5-E16.5). In cultured NSCs, knockdown of TIGAR reduced the expression of microtubule-associated protein 2 (MAP2), neuron-specific class III beta-tubulin (Tuj1), glial fibrillary acidic protein (GFAP), Ngn1, and NeuroD1, and enhanced the expression of REST, suggesting that TIGAR is an important regulator of NSC differentiation. Furthermore, TIGAR enhanced the expression of lactate dehydrogenase B (LDHB) and the mitochondrial biogenesis and oxidative phosphorylation (OXPHOS) markers, peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1α), nuclear respiratory factor (NRF1), and MitoNEET during NSC differentiation. TIGAR can decrease lactate production and accelerate oxygen consumption and ATP generation to maintain a high rate of OXPHOS in differentiated NSCs. Interestingly, knockdown of TIGAR decreased the level of acetyl-CoA and H3K9 acetylation at the promoters of Ngn1, Neurod1, and Gfap. Acetate, a precursor of acetyl-CoA, increased the level of H3K9 acetylation and rescued the effect of TIGAR deficiency on NSC differentiation. Together, our data demonstrated that TIGAR promotes metabolic reprogramming and regulates NSC differentiation through an epigenetic mechanism.

11.
Angew Chem Int Ed Engl ; 58(13): 4271-4275, 2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30730605

RESUMO

Incorporating atomically dispersed metal species into functionalized metal-organic frameworks (MOFs) can integrate their respective merits for catalysis. A cage-controlled encapsulation and reduction strategy is used to fabricate single Ru atoms and triatomic Ru3 clusters anchored on ZIF-8 (Ru1 @ZIF-8, Ru3 @ZIF-8). The highly efficient and selective catalysis for semi-hydrogenation of alkyne is observed. The excellent activity derives from high atom-efficiency of atomically dispersed Ru active sites and hydrogen enrichment by the ZIF-8 shell. Meanwhile, ZIF-8 shell serves as a novel molecular sieve for olefins to achieve absolute regioselectivity of catalyzing terminal alkynes but not internal alkynes. Moreover, the size-dependent performance between Ru3 @ZIF-8 and Ru1 @ZIF-8 is detected in experiment and understood by quantum-chemical calculations, demonstrating a new and promising approach to optimize catalysts by controlling the number of atoms.

12.
Mol Carcinog ; 58(6): 1008-1018, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30720232

RESUMO

Sohlh2 belongs to the superfamily of basic helix-loop-helix (bhlh) transcription factors. Aberrant expression of bhlh transcription factors has been shown to be associated with multiple tumorigenesis. We previously identified that sohlh2 functioned as a tumor suppressor in ovarian cancer. Here, we examined the expression levels of sohlh2 in human breast cancer and its potential role in disease pathogenesis. The results of sohlh2 immunohistochemistry (IHC) and Western blot analysis demonstrated the decreased sohlh2 expression in breast cancer specimens as compared to adjacent noncancerous tissues. Through in vitro MTT, BrdU, colony formation and cell cycle assays and in vivo tumor xenograft studies, we showed that forced expression of sohlh2 led to a significant reduction in proliferation due to G1 arrest in vitro and tumorigenesis in nude mice. Conversely, silencing of sohlh2 enhanced breast cancer cell proliferation. Furthermore, we confirmed that sohlh2 inhibited breast cancer cell proliferation by suppressing the Wnt/ß-catenin signaling pathway. APC was the direct target of sohlh2, and mediated the inhibitory activities of sohlh2 on Wnt/ß-catenin signaling pathway. Thus, our data indicate that sohlh2 likely functions as a tumor suppressor in breast cancer that is mediated by repressing Wnt/ß-catenin signaling pathway via upregulation of APC expression.


Assuntos
Proteína da Polipose Adenomatosa do Colo/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Neoplasias da Mama/patologia , Regulação para Baixo , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Feminino , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Humanos , Células MCF-7 , Camundongos , Transplante de Neoplasias , Regiões Promotoras Genéticas , Via de Sinalização Wnt
13.
Nat Commun ; 9(1): 5422, 2018 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-30575726

RESUMO

Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.

14.
J Am Chem Soc ; 140(24): 7407-7410, 2018 06 20.
Artigo em Inglês | MEDLINE | ID: mdl-29863867

RESUMO

The hydrosilylation reaction is one of the largest-scale application of homogeneous catalysis and is widely used to enable the commercial manufacture of silicon products. However, considerable issues including disposable platinum consumption, undesired side reactions and unacceptable catalyst residues still remain. Here, we synthesize a heterogeneous partially charged single-atom platinum supported on anatase TiO2 (Pt1δ+/TiO2) catalyst via an electrostatic-induction ion exchange and two-dimensional confinement strategy, which can catalyze hydrosilylation reaction with almost complete conversion and produce exclusive adduct. Density functional theory calculations reveal that unexpected property of Pt1δ+/TiO2 originates from atomic dispersion of active species and unique partially positive charge Ptδ+ electronic structure that conventional nanocatalysts do not possess. The fabrication of single-atom Pt1δ+/TiO2 catalyst accomplishes a reasonable use of Pt through recycling and maximum atom-utilized efficiency, indicating the potential to achieve a green hydrosilylation industry.

15.
Adv Mater ; 30(15): e1706508, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29508451

RESUMO

A novel polymer encapsulation strategy to synthesize metal isolated-single-atomic-site (ISAS) catalysts supported by porous nitrogen-doped carbon nanospheres is reported. First, metal precursors are encapsulated in situ by polymers through polymerization; then, metal ISASs are created within the polymer-derived p-CN nanospheres by controlled pyrolysis at high temperature (200-900 °C). Transmission electron microscopy and N2 sorption results reveal this material to exhibit a nanospheric morphology, a high surface area (≈380 m2 g-1 ), and a porous structure (with micropores and mesopores). Characterization by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure confirms the metal to be present as metal ISASs. This methodology is applicable to both noble and nonprecious metals (M-ISAS/p-CN, M = Co, Ni, Cu, Mn, Pd, etc.). In particular, the Co-ISAS/p-CN nanospheres obtained using this method show comparable (E1/2 = 0.838 V) electrochemical oxygen reduction activity to commercial Pt/C with 20 wt% Pt loading (E1/2 = 0.834 V) in alkaline media, superior methanol tolerance, and outstanding stability, even after 5000 cycles.

16.
Nat Commun ; 8(1): 591, 2017 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-28928359

RESUMO

Bio-oil, produced by the destructive distillation of cheap and renewable lignocellulosic biomass, contains high energy density oligomers in the water-insoluble fraction that can be utilized for diesel and valuable fine chemicals productions. Here, we show an efficient hydrodeoxygenation catalyst that combines highly dispersed palladium and ultrafine molybdenum phosphate nanoparticles on silica. Using phenol as a model substrate this catalyst is 100% effective and 97.5% selective for hydrodeoxygenation to cyclohexane under mild conditions in a batch reaction; this catalyst also demonstrates regeneration ability in long-term continuous flow tests. Detailed investigations into the nature of the catalyst show that it combines hydrogenation activity of Pd and high density of both Brønsted and Lewis acid sites; we believe these are key features for efficient catalytic hydrodeoxygenation behavior. Using a wood and bark-derived feedstock, this catalyst performs hydrodeoxygenation of lignin, cellulose, and hemicellulose-derived oligomers into liquid alkanes with high efficiency and yield.Bio-oil is a potential major source of renewable fuels and chemicals. Here, the authors report a palladium-molybdenum mixed catalyst for the selective hydrodeoxygenation of water-insoluble bio-oil to mixtures of alkanes with high carbon yield.

17.
Neuroscience ; 364: 45-59, 2017 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-28782640

RESUMO

The transition from multipotent neural stem cells (NSCs) to terminally differentiated neurons is a multistep process, and the transition is finely regulated by transcription factors with basic helix-loop-helix (bHLH) motifs. Melatonin is an endogenous neurohormone with profound neurotrophic and neuroprotective effects both during the embryonic developmental stage and adulthood. The effects of melatonin on the differentiation of NSCs have been reported, and these effects may be responsible for its neuroprotective properties. However, the mechanisms underlying the effects of melatonin are not well understood. It is unclear whether melatonin affects the expression of bHLH factors at the onset of neuronal differentiation, and the molecular mechanisms involved still need to be further explored. Using mouse NSCs, we identified a novel role for melatonin in the epigenetic regulation of bHLH factors during neuronal differentiation. Our data showed that melatonin promoted neuronal differentiation by specifically increasing the acetylation of histone H3 lysine14 (H3K14). Increased H3K14 acetylation altered the chromatin state of the promoters of bHLH factors Neurogenin1 and NeuroD1 and activated their transcription; then, Neurogenin1 and NeuroD1 initiated and sustained the commitment to neuronal fates. As we know, CBP/p300 is an important class of histone acetyltransferases that acetylate histone H3K14, we found that melatonin activated the histone acetyltransferase activity of CREB-binding protein (CBP)/p300 via ERK signaling pathways. For the first time, we systematically showed the molecular mechanism of action of melatonin, which suggested that melatonin functions as a regulator of the acetylation-dependent gene expression network.


Assuntos
Proteína de Ligação a CREB/metabolismo , Diferenciação Celular/fisiologia , Proteína p300 Associada a E1A/metabolismo , Histonas/metabolismo , Lisina/metabolismo , Sistema de Sinalização das MAP Quinases/fisiologia , Melatonina/metabolismo , Células-Tronco Neurais/metabolismo , Acetilação , Animais , Camundongos
18.
J Am Chem Soc ; 139(29): 9795-9798, 2017 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-28696113

RESUMO

Here we report a novel approach to synthesize atomically dispersed uniform clusters via a cage-separated precursor preselection and pyrolysis strategy. To illustrate this strategy, well-defined Ru3(CO)12 was separated as a precursor by suitable molecular-scale cages of zeolitic imidazolate frameworks (ZIFs). After thermal treatment under confinement in the cages, uniform Ru3 clusters stabilized by nitrogen species (Ru3/CN) were obtained. Importantly, we found that Ru3/CN exhibits excellent catalytic activity (100% conversion), high chemoselectivity (100% for 2-aminobenzaldehyde), and significantly high turnover frequency (TOF) for oxidation of 2-aminobenzyl alcohol. The TOF of Ru3/CN (4320 h-1) is about 23 times higher than that of small-sized (ca. 2.5 nm) Ru particles (TOF = 184 h-1). This striking difference is attributed to a disparity in the interaction between Ru species and adsorbed reactants.

19.
Angew Chem Int Ed Engl ; 56(24): 6937-6941, 2017 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-28402604

RESUMO

The development of low-cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single-atom Fe/N-doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half-wave potential (E1/2 ) of 0.900 V, which outperformed commercial Pt/C and most non-precious-metal catalysts reported to date. Besides exceptionally high kinetic current density (Jk ) of 37.83 mV cm-2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.

20.
J Am Chem Soc ; 139(15): 5494-5502, 2017 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-28343390

RESUMO

The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the Rh2P NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.

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