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1.
Adv Mater ; : e2000380, 2020 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-32329189

RESUMO

Boosting charge transfer in materials is critical for applications involving charge carriers. Engineering ionic channels in electrode materials can create a skeleton to manipulate their ion and electron behaviors with favorable parameters to promote their capacity and stability. Here, tailoring of the atomic structure in layered potassium niobate (K4 Nb6 O17 ) nanosheets and facilitating their application in lithium and potassium storage by dehydration-triggered lattice rearrangement is reported. The spectroscopy results reveal that the interatomic distances of the NbO coordination in the engineered K4 Nb6 O17 are slightly elongated with increased degrees of disorder. Specifically, the engineered K4 Nb6 O17 shows enhanced electrical and ionic conductivity, which can be attributed to the enlarged interlamellar spacing and subtle distortions in the fine atomic arrangements. Moreover, subsequent experimental results and calculations demonstrate that the energy barrier for Li+ /K+ diffusion is significantly lower than that in pristine K4 Nb6 O17 . Interestingly, the diffusion coefficient of K+ is one order of magnitude higher than that of Li+ , and the engineered K4 Nb6 O17 presents superior electrochemical performance for K+ to Li+ . This work offers an ionic engineering strategy to enable fast and durable charge transfer in materials, holding great promise for providing guidance for the material design of related energy storage systems.

2.
Small ; : e2000421, 2020 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-32227457

RESUMO

The electrochemical N2 reduction reaction (NRR) is emerging as a promising alternative to the industrial Haber-Bosch process for distributed and modular production of NH3 . Nevertheless, developing high-efficiency catalysts to simultaneously realize both high activity and selectivity for the development of a sustainable NRR is very critical but extremely challenging. Here, a unique plasma-assisted strategy is developed to synthesize iridium diphosphide nanocrystals with abundant surface step atoms anchored in P,N-codoped porous carbon nanofilms (IrP2 @PNPC-NF), where the edges of the IrP2 nanocrystals are extremely irregular, and the ultrathin PNPC-NF possesses a honeycomb-like macroporous structure. These characteristics ensure that IrP2 @PNPC-NF delivers superior NRR performance with an NH3 yield rate of 94.0 µg h-1 mg-1 cat. and a faradaic efficiency (FE) of 17.8%. Density functional theory calculations reveal that the unique NRR performance originates from the low-coordinate step atoms on the edges of IrP2 nanocrystals, which can lower the reaction barrier to improve the NRR activity and simultaneously inhibit hydrogen evolution to achieve a high FE for NH3 formation. More importantly, such a plasma-assisted strategy is general and can be extended to the synthesis of other high-melting-point noble-metal phosphides (OsP2 @PNPC-NF, Re3 P4 @PNPC-NF, etc.) with abundant step atoms at lower temperatures.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32207203

RESUMO

Spinel LiNi0.5 Mn1.5 O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd 3 ‾ m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2 O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices.

4.
Nano Lett ; 20(3): 2034-2046, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32019311

RESUMO

Tin-based composites hold promise as anodes for high-capacity lithium/sodium-ion batteries (LIBs/SIBs); however, it is necessary to use carbon coated nanosized tin to solve the issues related to large volume changes during electrochemical cycling, thus leading to the low volumetric capacity for tin-based composites due to their low packing density. Herein, we design a highly dense graphene-encapsulated nitrogen-doped carbon@Sn (HD N-C@Sn/G) compact monolith with Sn nanoparticles double-encapsulated by N-C and graphene, which exhibits a high density of 2.6 g cm-3 and a high conductivity of 212 S m-1. The as-obtained HD N-C@Sn/G monolith anode exhibits ultrahigh and durable volumetric lithium/sodium storage. Specifically, it delivers a high volumetric capacity of 2692 mAh cm-3 after 100 cycles at 0.1 A g-1 and an ultralong cycling stability exceeding 1500 cycles at 1.0 A g-1 with only 0.019% capacity decay per cycle in lithium-ion batteries. Besides, in situ TEM and ex situ SEM have revealed that the unique double-encapsulated structure effectively mitigates drastic volume variation of the tin nanoparticles during electrode cycling. Furthermore, the full cell using HD N-C@Sn/G as an anode and LiCoO2 as a cathode displays a superior cycling stability. This work provides a new avenue and deep insight into the design of high-volumetric-capacity alloy-based anodes with ultralong cycle life.

5.
Chem Asian J ; 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-32073755

RESUMO

Carbon is a simple, stable and popular element with many allotropes. The carbon family members include carbon dots, carbon nanotubes, carbon fibers, graphene, graphite, graphdiyne and hard carbon, etc. They can be divided into different dimensions, and their structures can be open and porous. Moreover, it is very interesting to dope them with other elements (metal or non-metal) or hybridize them with other materials to form composites. The elemental and structural characteristics offer us to explore their applications in energy, environment, bioscience, medicine, electronics and others. Among them, energy storage and conversion are extremely attractive, as advances in this area may improve our life quality and environment. Some energy devices will be included herein, such as lithium-ion batteries, lithium sulfur batteries, sodium-ion batteries, potassium-ion batteries, dual ion batteries, electrochemical capacitors, and others. Additionally, carbon-based electrocatalysts are also studied in hydrogen evolution reaction and carbon dioxide reduction reaction. However, there are still many challenges in the design and preparation of electrode and electrocatalytic materials. The research related to carbon materials for energy storage and conversion is extremely active, and this has motivated us to contribute with a roadmap on 'Carbon Materials in Energy Storage and Conversion'.

6.
Proc Natl Acad Sci U S A ; 117(6): 2815-2823, 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-31996477

RESUMO

Existing lithium-ion battery technology is struggling to meet our increasing requirements for high energy density, long lifetime, and low-cost energy storage. Here, a hybrid electrode design is developed by a straightforward reengineering of commercial electrode materials, which has revolutionized the "rocking chair" mechanism by unlocking the role of anions in the electrolyte. Our proof-of-concept hybrid LiFePO4 (LFP)/graphite electrode works with a staged deintercalation/intercalation mechanism of Li+ cations and PF6 - anions in a broadened voltage range, which was thoroughly studied by ex situ X-ray diffraction, ex situ Raman spectroscopy, and operando neutron powder diffraction. Introducing graphite into the hybrid electrode accelerates its conductivity, facilitating the rapid extraction/insertion of Li+ from/into the LFP phase in 2.5 to 4.0 V. This charge/discharge process, in turn, triggers the in situ formation of the cathode/electrolyte interphase (CEI) layer, reinforcing the structural integrity of the whole electrode at high voltage. Consequently, this hybrid LFP/graphite-20% electrode displays a high capacity and long-term cycling stability over 3,500 cycles at 10 C, superior to LFP and graphite cathodes. Importantly, the broadened voltage range and high capacity of the hybrid electrode enhance its energy density, which is leveraged further in a full-cell configuration.

7.
ACS Appl Mater Interfaces ; 12(5): 5958-5967, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31922398

RESUMO

The practical application of Li-S batteries is hampered because of their poor cycling stability caused by electrolyte-dissolved lithium polysulfides. Dual functionalities such as strong chemical adsorption stability and high conductivity are highly desired for an ideal host material for the sulfur-based cathode. Herein, a uniform polypyrrole layer-coated sulfur/graphene aerogel composite is designed and synthesized using a novel vapor-phase deposition method. The polypyrrole layer simultaneously acts as a host and an adsorbent for efficient suppression of polysulfide dissolution through strong chemical interaction. The density functional theory calculations reveal that the polypyrrole could trap lithium polysulfides through stronger bonding energy. In addition, the deflation of sulfur/graphene hydrogel during the vapor-phase deposition process enhances the contact of sulfur with matrices, resulting in high sulfur utilization and good rate capability. As a result, the synthesized polypyrrole-coated sulfur/graphene aerogel composite delivers specific discharge capacities of 1167 and 409.1 mA h g-1 at 0.2 and 5 C, respectively. Moreover, the composite can maintain a capacity of 698 mA h g-1 at 0.5 C after 500 cycles, showing an ultraslow decay rate of 0.03% per cycle.

8.
Adv Mater ; 32(2): e1905632, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31777986

RESUMO

Topological insulators have spurred worldwide interest, but their advantageous properties have scarcely been explored in terms of electrochemical energy storage, and their high-rate capability and long-term cycling stability still remain a significant challenge to harvest. p-Type topological insulator SnSb2 Te4 nanodots anchoring on few-layered graphene (SnSb2 Te4 /G) are synthesized as a stable anode for high-rate lithium-ion batteries and potassium-ion batteries through a ball-milling method. These SnSb2 Te4 /G composite electrodes show ultralong cycle lifespan (478 mAh g-1 at 1 A g-1 after 1000 cycles) and excellent rate capability (remaining 373 mAh g-1 even at 10 A g-1 ) in Li-ion storage owing to the rapid ion transport accelerated by the PN heterojunction, virtual electron highways provided by the conductive topological surface state, and extraordinary pseudocapacitive contribution, whose excellent phase reversibility is confirmed by synchrotron in situ X-ray powder diffraction. Surprisingly, durable lifespan even at practical levels of mass loading (>10 mg cm-2 ) for Li-ion storage and excellent K-ion storage performance are also observed. This work provides new insights for designing high-rate electrode materials by boosting conductive topological surfaces, atomic doping, and the interface interaction.

9.
Angew Chem Int Ed Engl ; 59(9): 3638-3644, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-31840345

RESUMO

Potassium-ion batteries are promising for low-cost and large-scale energy storage applications, but the major obstacle to their application is the lack of safe and effective electrolytes. A phosphate-based fire retardant such as triethyl phosphate is now shown to work as a single solvent with potassium bis(fluorosulfonyl)imide at 0.9 m, in contrast to previous Li and Na systems where phosphates cannot work at low concentrations. This electrolyte is optimized at 2 m, where it exhibits the advantages of low cost, low viscosity, and high conductivity, as well as the formation of a uniform and robust salt-derived solid-electrolyte interphase layer, leading to non-dendritic K-metal plating/stripping with Coulombic efficiency of 99.6 % and a highly reversible graphite anode.

10.
Angew Chem Int Ed Engl ; 59(9): 3470-3474, 2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-31828926

RESUMO

Metal-CO2 batteries have attracted much attention owing to their high energy density and use of greenhouse CO2 waste as the energy source. However, the increasing cost of lithium and the low discharge potential of Na-CO2 batteries create obstacles for practical applications of Li/Na-CO2 batteries. Recently, earth-abundant potassium ions have attracted considerable interest as fast ionic charge carriers for electrochemical energy storage. Herein, we report the first K-CO2 battery with a carbon-based metal-free electrocatalyst. The battery shows a higher theoretical discharge potential (E⊖ =2.48 V) than that of Na-CO2 batteries (E⊖ =2.35 V) and can operate for more than 250 cycles (1500 h) with a cutoff capacity of 300 mA h g-1 . Combined DFT calculations and experimental observations revealed a reaction mechanism involving the reversible formation and decomposition of P121 /c1-type K2 CO3 at the efficient carbon-based catalyst.

11.
Small ; : e1903934, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31657137

RESUMO

The great demand for high-energy-density batteries has driven intensive research on the Li-S battery due to its high theoretical energy density. Consequently, considerable progress in Li-S batteries is achieved, although the lithium anode material is still challenging in terms of lithium dendrites and its unstable interface with electrolyte, impeding the practical application of the Li-S battery. Li2 S-based Li-ion sulfur batteries (LISBs), which employ lithium-metal-free anodes, are a convenient and effective way to avoid the use of lithium metal for the realization of practical Li-S batteries. Over the past decade, studies on LISBs are carried out to optimize their performance. Herein, the research progress and challenges of LISBs are reviewed. Several important aspects of LISBs, including their working principle, the physicochemical properties of Li2 S, Li2 S cathode material composites, LISBs full batteries, and electrolyte for Li2 S cathode, are extensively discussed. In particular, the activation barrier in the initial charge process is fundamentally analyzed and the mechanism is discussed in detail, based on previous reports. Finally, perspectives on the future direction of the research of LISBs are proposed.

12.
ACS Appl Mater Interfaces ; 11(41): 37726-37731, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31549805

RESUMO

Lithium metal anodes (LMAs) are critical for high-energy-density batteries such as Li-S and Li-O2 batteries. The spontaneously formed solid electrolyte interface on LMAs is fragile, which may not accommodate the cyclic Li plating/stripping. This usually will result in a low coulombic efficiency (CE), short cycle life, and potential safety hazards induced by the uncontrollable growth of lithium dendrites. In this study, we fabricate a Li alginate-based artificial SEI (ASEI) layer that is chemically stable and allows easy Li ion transport on the surface of LMAs, thus enabling the stable operation of lithium metal anodes. Compared to bare LMAs, the ASEI layer-protected LMAs exhibit a more stable Li plating/stripping behavior and present effective dendrite suppression. The symmetric Li∥Li cells with the ASEI layer-protected LMAs can stably run for 850 and 350 h at current densities of 0.5 and 1 mA cm-2, respectively. Additionally, the LiFePO4∥Li full cell with the ASEI layer-protected LMA exhibits a capacity retention of about 94.0% coupled with a CE of 99.6% after 1000 cycles at 4 C. We believe that this study of engineering an ASEI brings a new and promising approach to the stabilization of LMAs for high-performance lithium metal batteries.

13.
ACS Appl Mater Interfaces ; 11(40): 36742-36750, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31532608

RESUMO

A multifunctional coating with high ionic and electronic conductivity is constructed on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) to boost the battery stability upon cycling and during storage as well. Phosphoric acid reacts with residual lithium species on the pristine NCM to form a Li3PO4 coating with extra carbon nanotubes (CNTs) penetrating through, which shows high ionic and electronic conductivity. NCM, Li3PO4, CNTs, and the electrolyte jointly form a four-phase cathode electrolyte interface, which plays a key role in the great enhancement of capacity retention, from 50.3% for pristine NCM to 84.8% for the modified one after 500 cycles at 0.5C at room temperature. The modified NCM also delivers superior electrochemical performances at a high cut-off voltage (4.5 V), high temperature (55 °C), and high rate (10C). Furthermore, it can deliver 154.2 mA h g-1 at the 500th cycle after exposed to air with high humidity for 2 weeks. These results demonstrate that the well-constructed multifunctional coating can remarkably enhance the chemical and electrochemical performances of NCM. The improved cycling, storage, and rate performance are attributed to the four-phase cathode electrolyte interface delivering high electron and ionic conductivity and securing the cathode against attack. This work broadens the horizon for constructing effective electrode/electrolyte interfaces for electrochemical energy storage and conversion.

14.
ACS Nano ; 13(10): 11665-11675, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31508937

RESUMO

As an important class of multielectron reaction materials, the applications of transition-metal oxides (TMOs) are impeded by volume expansion and poor electrochemical activity. To address these intrinsic limitations, the renewal of TMOs inspires research on incorporating an advanced interface layer with multiple anionic characteristics, which may add functionality to support properties inaccessible to a single-anion TMO electrode. Herein, a transition-metal oxycarbide (TMOC, M = Mo) with more than one anionic species was prepared as an interface layer on a corresponding oxide. A multiple anionic TMOC possesses advantages of structural stability, abundant active sites, and elevated metal cation valence states. Such merits mitigate volume changes and enhance multielectron reactions significantly. The TMOC nanocomposite has a well-maintained capacity after 1000 cycles at 2 A·g-1 and fully resumed rate performance. In situ synchrotron X-ray powder diffraction (SXRPD) analysis unveils negligible volume expansions occurring upon oxycarbide layer coupling, with lattice spacing variation less than 1% during cycling. The lithium storage mechanism is further inspected by combined analysis of kinetics, SXRPD, and first-principles calculations. Superior to TMO, multielectron reactions of the TMOC electrode have been boosted due to easier rupture of the metal-oxygen bond. Such improvements underscore the importance of incorporating an oxycarbide configuration as a strategy to expand applications of TMOs.

15.
Angew Chem Int Ed Engl ; 58(49): 17709-17717, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31476103

RESUMO

Maximizing the activity of materials towards the alkaline hydrogen evolution reaction while maintaining their structural stability under realistic working conditions remains an area of active research. Herein, we report the first controllable surface modification of graphene(G)/V8 C7 heterostructures by nitrogen. Because the introduced N atoms couple electronically with V atoms, the V sites can reduce the energy barrier for water adsorption and dissociation. Investigation of the multi-regional synergistic catalysis on N-modified G/V8 C7 by experimental observations and density-functional-theory calculations reveals that the increase of electron density on the epitaxial graphene enable it to become favorable for H* adsorption and the subsequent reaction with another H2 O molecule. This work extends the range of surface-engineering approaches to optimize the intrinsic properties of materials and could be generalized to the surface modification of other transition-metal carbides.

16.
Small ; 15(44): e1903652, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31529600

RESUMO

The feasibility of transition metal carbides (TMCs) as promising high-rate electrodes is still hindered by low specific capacity and sluggish charge transfer kinetics. Improving charge transport kinetics motivates research toward directions that would rely on heterostructures. In particular, heterocomposing with carbon-rich TMCs is highly promising for enhancing Li storage. However, due to limited synthesis methods to prepare carbon-rich TMCs, understanding the interfacial interaction effect on the high-rate performance of TMCs is often neglected. In this work, a novel strategy is proposed to construct a binary carbide heteroelectrode, i.e. incorporating the carbon-rich TMC (M=Mo) with its metal-rich TMC nanowires (nws) via an ingenious in situ disproportionation reaction. Results show that the as-prepared MoC-Mo2 C-heteronanowires (hnws) electrode could fully recover its capacity after high-rates testing, and also possesses better lithium accommodation performance. Kinetic analysis verified that both electron and ion transfer in MoC-Mo2 C-hnws are superior to those of its singular counterparts. Such improvements suggest that by taking utilization of the interfacial component interactions of stoichiometry tunable heterocarbides, the electrochemical performance, especially high-rate capability of carbides, could be significantly enhanced.

17.
Adv Mater ; : e1904528, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31544298

RESUMO

The performance of rechargeable batteries is influenced by the structural and phase changes of components during cycling. Neutron powder diffraction (NPD) provides unique and useful information concerning the structure-function relation of battery components and can be used to study the changes to component phase and structure during battery cycling, known as in operando measurement studies. The development and use of NPD for in operando measurements of batteries is summarized along with detailed experimental approaches that impact the insights gained by these. A summary of the information gained concerning battery function using in operando NPD measurements is provided, including the structural and phase evolution of electrode materials and charge-carrying ion diffusion pathways through these, which are critical to the development of battery technology.

18.
ACS Nano ; 13(10): 11843-11852, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31545592

RESUMO

Vacancy engineering is a promising approach for optimizing the energy storage performance of transition metal dichalcogenides (TMDs) due to the unique properties of vacancies in manipulating the electronic structure and active sites. Nevertheless, achieving effective introduction of anion vacancies with adjustable vacancy concentration on a large scale is still a big challenge. Herein, MoS2(1-x)Se2x alloys with anion vacancies introduced in situ have been achieved by a simple alloying reaction, and the vacancy concentration has been optimized through adjusting the chemical composition. Experimental and density functional theory calculation results suggest that the anion vacancies in MoS2(1-x)Se2x alloys could enhance the electronic conductivity, induce more active sites, and alleviate structural variation in the alloys during the potassium storage process. When applied as potassium ion battery anodes, the most optimized vacancy-rich MoSSe alloy delivered high reversible capacities of 517.4 and 362.4 mAh g-1 at 100 and 1000 mA g-1, respectively. Moreover, a reversible capacity of 220.5 mAh g-1 could be maintained at 2000 mA g-1 after 1000 cycles. This work demonstrates a practical approach to modifying the electronic and defect properties of TMDs, providing an effective strategy for constructing advanced electrode materials for battery systems.

19.
ACS Appl Mater Interfaces ; 11(36): 33022-33032, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31424188

RESUMO

Electrode materials that act through the electrochemical conversion mechanism, such as metal selenides, have been considered as promising anode candidates for lithium-ion batteries (LIBs), although their fast capacity attenuation and inadequate electrical conductivity are impeding their practical application. In this work, these issues are addressed through the efficient fabrication of MnSe nanoparticles inside porous carbon hierarchical architectures for evaluation as anode materials for LIBs. Density functional theory simulations indicate that there is a completely irreversible phase transformation during the initial cycle, and the high structural reversibility of ß-MnSe provides a low energy barrier for the diffusion of lithium ions. Electron localization function calculations demonstrate that the phase transformation leads to high charge transfer kinetics and a favorable lithium ion diffusion coefficient. Benefitting from the phase transformation and unique structural engineering, the MnSe/C chestnut-like structures with boosted conductivity deliver enhanced lithium storage performance (885 mA h g-1 at a current density of 0.2 A g-1 after 200 cycles), superior cycling stability (a capacity of 880 mA h g-1 at 1 A g-1 after 1000 cycles), and outstanding rate performance (416 mA h g-1 at 2 A g-1).

20.
ACS Nano ; 13(8): 9376-9385, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31330108

RESUMO

Solid materials with special atomic and electronic structures are deemed desirable platforms for establishing clear relationships between surface/interface structure characteristics and electrochemical activity. In this work, nickel boride (NixB) and nickel boride/graphene (NixB/G) are chosen as positive materials of supercapacitors. The NixB/G displays higher specific capacitance (1822 F g-1) than that of NixB (1334 F g-1) at 1 A g-1, and it still maintains 1179 F g-1 at 20 A g-1, suggesting the high rate performance. The asymmetric supercapacitor device (NixB/G//activated carbon) also delivered a very high energy density of 50.4 Wh kg-1, and the excellent electrochemical performance is ascribed to the synergistic effect of NixB, Ni(BO2)2, and graphene that fully enhances the diffusion of OH- and the electron transport. During the cycles, the prepared ultrafine NixB nanoparticles will be gradually in situ converted into ß-Ni(OH)2 which has a smaller particle size than that prepared by other methods. This will enhance the utilization of Ni(OH)2 and decrease the ion diffusion distance. The electron deficient state of B in Ni(BO2)2 amorphous shell will make it easy to accept extra electrons, enhancing the adsorption of OH- at the shell surface. Moreover, Ni(BO2)2 makes strong adhesion between NixB (or ß-Ni(OH)2) and graphene and protects the core structure in a stable state, extending the cycle life. The above properties of NixB/G endow the electrode good capacitive performance.

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