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Anode-free lithium metal batteries (AFLBs) have attracted considerable attention due to their high theoretical specific capacity and absence of Li. However, the heterogeneous Li deposition and stripping on the lithiophobic Cu collector hamper AFLBs in practice. To achieve a uniform and reversible Li deposition, a carbon-based layer on the Cu collector has attracted intense interest due to its high conductivity. However, the 2D single-component carbon-based interface is inadequate lithiophilic for obtaining the homogeneous Li deposition and preventing the lithium dendrite from piercing the separator. Herein, we present a 3D embedded lithiophilic SiO2 nanoparticles-graphene nanosheet matrix (SiO2@G-M) on the Cu collector by organic nano carbon source. In this structure, the lithiophilic SiO2 nanoparticles as active points promote the homogeneous lithium nucleation and the 3D graphene nanosheet matrix offers homogenous electron distribution and voids to prevent the piercing. Finally, SiO2@G-M/Li cell shows a high coulombic efficiency of 98.62 % after 100 cycles at a high current density of 2 mA cm-2 with an areal capacity of 1 mAh cm-2.
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The design and construction of highly efficient electrocatalysts for overall water splitting and urea electrolysis are significantly important for promoting energy conversion and realizing green hydrogen production. In this work, we constructed a multi-phase heterojunction through a simple hydrothermal and phosphorization process. The P-doped NiFe2O4 (P-NiFe2O4) nanoparticles were uniformly anchored on the bamboo-like N-doped carbon nanotubes (NCNTs) grown via a NiFe-alloy autocatalysis. The electronic structure and coordination environment of active species were optimized by the synergistic action of P doping, well-dispersed ultrafine NiFe2O4, and NCNTs matrix with good conductivity, enhancing their quantity and activity for electrocatalysis. Consequently, the P-NiFe2O4/NCNTs/NiFe exhibits excellent HER and OER activities with an overpotential of 111 and 266â mV at 10â mA cm-2 in 1â M KOH, respectively. The symmetrical overall water-splitting cell using P-NiFe2O4/NCNTs/NiFe as both anode and cathode delivers 10â mA cm-2 at a voltage of 1.604â V in 1â M KOH. Notably, the two-electrode cell requires a low voltage of 1.467â V to achieve a current density of 10â mA cm-2 in 1â M KOH solution with 0.6â M urea. This designed catalysts display outstanding reaction kinetics and catalytic stability. This work provides useful guidance for applying transition metal-based catalysts for hydrogen production.
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Metal-halide perovskite nanocrystals (NCs) are one of the most promising emitters for the application of display and nanolight sources. The full width at half-maximum (FWHM) of photoluminescence (PL) emission is essential for color purity, which however remains a difficulty to further reduce the FWHM of the perovskite NCs at room temperature. Here, we show the quasi-sphere perovskite NCs with narrow PL emission at a deep-blue wavelength of â¼430 nm; its PL FWHM reaches â¼11 nm at room temperature, owing to the monodispersion in size distribution as well as the symmetric quasi-sphere morphology of NCs releasing the fine structure splitting-induced inhomogeneous broadening. Through regulating A cations with respect to the ratio of FA (or MA)-to-Cs and Cs-to-Pb, the PL emission of the NCs could be tuned from â¼505 to â¼430 nm combined with varied morphologies from large cube to small quasi-sphere. Such spectroscopic and morphological discrepancies are supposed to be attributed to the different crystalline kinetics that is strongly dependent on the synthetic condition. To be specific, in the case of increasing FA (or MA)-to-Cs, the growth rate of CsPbBr3 and FAPbBr3 (or MAPbBr3) perovskites is determined by the reactivity of transient species, while in the case of decreasing the Cs-to-Pb ratio, the growth rate of perovskites is slowed down by the serious reduction of Cs+ in the precursor. This study provides an effective strategy to adjust the emission across from green to deep-blue color and promotes the perovskite NCs with a narrow FWHM, and tunable PL emission facilitates in application of optoelectronic devices.
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The design and synthesis of efficient, inexpensive, and long-term stable heterostructured electrocatalysts with high-density dislocations for hydrogen evolution reaction in alkaline media and seawater are still a great challenge. An amorphous/crystalline/amorphous sandwiched structure with abundant dislocations were synthesized through thermal phosphidation strategies. The dislocations play an important role in the hydrogen evolution reactions. Copious dislocation defects, combined with cracks, and the synergistic interfacial effect between crystalline phase and amorphous phase regulate the electronic structure of electrocatalyst, provide more active sites, and thus endow the electrocatalysts with excellent catalytic activity under alkaline water and seawater. The overpotentials of P-NiMoO4 at 10 mA/cm2 in 1 M KOH aqueous solution and seawater are 45 and 75 mV, respectively. Additionally, the P-NiMoO4 electrocatalyst exhibits long-term stability over 100 h. This study provides a simple approach for synthesizing amorphous/crystalline/amorphous sandwiched non-noble-metal electrocatalysts with abundant dislocations for hydrogen evolution reaction.
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Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity and energy density, which are considered to be very promising energy storage devices. However, the slow redox kinetics of polysulfides are the main reason for the rapid capacity decay of Li-S batteries. A reasonable electrocatalyst for the Li-S battery should reduce the reaction barrier and accelerate the reaction kinetics of the bidirectional catalytic conversion of lithium polysulfides (LiPSs), thereby reducing the cumulative concentration of LiPSs in the electrolyte. In this report, porous N-doped carbon nanofibers decorated with independent dual metal sites as catalysts for Li-S batteries were fabricated in one step using a fusion-foaming method. Experimental and theoretical analyses demonstrate that the synergistic effect of independent dual metal sites provides strong LiPS affinity, improved electronic conductivity, and enhanced redox kinetics of polysulfides. Therefore, the assembled Li-S battery exhibits high rate performance (discharge specific capacity of 771 mA h g-1 at 2C) and excellent cycle stability (capacity decay rate of 0.51% after 1000 cycles at 1C).
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Black phosphorus (BP), as a burgeoning two-dimensional material, has shown good electrocatalytic activity due to its unique electronic structure and abundant active sites.However, the presence of lone pair electrons in black phosphorus leads to its poor stability and rapid degradation in an oxygen/water environment, which greatly limits its practical application. Herein, BP-Co heterojunctions were synthesized on carbon nanotube@nitrogen-doped carbon (BP-Co/CNT@NC) by the pyrolysis of ZnCo-zeolitic imidazolate frameworks and subsequent solvothermal treatment. The BP-Co Schottky junction improved the electrocatalytic stability of BP, modulated its electronic structure, improved its conductivity and electron transfer during the electrocatalytic reaction. Density functional theory calculation was used to confirm the electron transfer and redistribution at the interface between BP and Co, which constructed an oppositely charged region and formed a strong built-in field. Energy band configuration analysis revealed a narrowed band gap because of the formation of BP-Co Schottky junction. Consequently, the optimized BP-Co/CNT@NC exhibited a superior oxygen evolution reaction (OER) performance, a low overpotential of 370 mV@100 mA/cm2, with a small Tafel slope of 40 mV/dec and good long-term stability. Particularly, the catalyst has an excellent OER performance at the high current density of 100-400 mA/cm2. This strategy improves the stability of BP electrocatalysts and strengthens their utilization in electrocatalytic applications.
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Despite stunning progress in single-atom catalysis (SAC), it remains a grand challenge to yield a high loading of single atoms (SAs) anchored on substrates. Herein, we report a one-step laser-planting strategy to craft SAs of interest under an atmospheric temperature and pressure on various substrates including carbon, metals, and oxides. Laser pulses render concurrent creation of defects on the substrate and decomposition of precursors into monolithic metal SAs, which are immobilized on the as-produced defects via electronic interactions. Laser planting enables a high defect density, leading to a record-high loading of SAs of 41.8 wt %. Our strategy can also synthesize high-entropy SAs (HESAs) with the coexistence of multiple metal SAs, regardless of their distinct characteristics. An integrated experimental and theoretical study reveals that superior catalytic activity can be achieved when the distribution of metal atom content in HESAs resembles the distribution of their catalytic performance in a volcano plot of electrocatalysis. The noble-metal mass activity for a hydrogen evolution reaction within HESAs is 11-fold over that of commercial Pt/C. The laser-planting strategy is robust, opening up a simple and general route to attaining an array of low-cost, high-density SAs on diverse substrates under ambient conditions for electrochemical energy conversion.
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Pursuing high power density lithium metal battery with high safety is essential for developing next-generation energy-storage devices, but uncontrollable electrolyte degradation and the consequence formed unstable solid-electrolyte interface (SEI) make the task really challenging. Herein, an ionic liquid (IL) confined MOF/Polymer 3D-porous membrane was constructed for boosting in situ electrochemical transformations of Janus-heterarchical LiF/Li3 N-rich SEI films on the nanofibers. Such a 3D-Janus SEI-incorporated into the separator offers fast Li+ transport routes, showing superior room-temperature ionic conductivity of 8.17×10-4 â S cm-1 and Li+ transfer number of 0.82. The cryo-TEM was employed to visually monitor the in situ formed LiF and Li3 N nanocrystals in SEI and the deposition of Li dendrites, which is greatly benefit to the theoretical simulation and kinetic analysis of the structural evolution during the battery charge and discharge process. In particular, this membrane with high thermal stability and mechanical strength used in solid-state Li||LiFePO4 and Li||NCM-811 full cells and even in pouch cells showed enhanced rate-performance and ultra-long life spans.
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Lithium-sulfur battery is one of the most promising candidates for next-generation energy storage systems, but the serious shuttle effect and sluggish reaction kinetics of polysulfides impair its practical applications. Herein, sulfur-deficient MoS2/carbon hollow nanospheres (MoS2-CHNs) are firstly synthesized by a NaCl-template pyrolysis and employed as sulfur host for lithium-sulfur batteries. TEM analysis reveals that carbon hollow nanospheres existing in the composite are the backbones that help to immobilize the ultrathin MoS2 nanosheets and ensure their large specific surface area. The MoS2 nanosheets consist of 5-10 layers of MoS2 with rich sulfur vacancies. The first principle calculation demonstrates that sulfur vacancy led to an intensively enhanced binding energy (-4.70 eV) towards Li2S6 compared to the pristine MoS2 (-1.57 eV). It suppressed the shuttle effect efficiently. The catalytic experiments reveal that MoS2-CHNs have a superior ability for the nucleation of Li2S and bidirectional electrocatalytic capability for the conversion of polysulfide. The large storage space inside MoS2-CHNs can work as a reservoir for intermediate polysulfides to substantially reduce the concentration overpotential. Due to this advantageous structural design of MoS2-CHNs electrode, its reversible capacity remains 1139 mAh g-1 after 100 cycles at 0.2C, and 600 mAh g-1 after 500 cycles at 5C with a sulfur loading of 5 mg cm-2. Even though the sulfur loading increases to 10 mg cm-2, the Li-S battery delivers a stable capacity of 978 mAh g-1 after 50 cycles at 0.2C. So the MoS2-CHNs demonstrate a promising application for high-energy Li-S batteries.
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Carbono , Nanosferas , Molibdênio , Lítio , EnxofreRESUMO
Transition metal nanostructures are widely regarded as important catalysts to replace the precious metal Pt for hydrogen evolution reaction (HER) in water splitting. However, it is difficult to obtain uniform-sized and ultrafine metal nanograins through general high-temperature reduction and sintering processes. Herein, a novel method of chemical energy-driven lithiation is introduced to synthesize transition metal nanostructures. By taking advantage of the slow crystallization kinetics at room temperature, more surface and boundary defects can be generated and remained, which reduce the atomic coordination number and tune the electronic structure and adsorption free energy of the metals. The obtained Ni nanostructures therein exhibit excellent HER performance. In addition, the bimetal of Co and Ni shows better electrocatalytic kinetics than individual Ni and Co nanostructures, reaching 100 mA cm-2 at a low overpotential of 127 mV. The high HER performance originates from well-formed synergistic effect between Ni and Co by tuning the electronic structures. Density functional theory simulations confirm that the bimetallic NiCo possesses a low Gibbs free energy of hydrogen adsorption, which are conducive to enhance its intrinsic activity. This work provides a general strategy that enables simultaneous defect engineering and electronic modulation of transition metal catalysts to achieve an enhancement in HER performance.
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Developing zero-strain electrode materials with high capacity is crucial for lithium-ion batteries (LIBs). Here, a new zero-strain composite material made of ultrasmall Si nanodots (NDs) within metal organic framework-derived nanoreactors (Si NDsâMDN) through a novel space-confined catalytic strategy is reported. The unique Si NDsâMDN anode features a low strain (<3%) and a high theoretical lithium storage capacity (1524 mAh g-1 ) which far surpasses the traditional single-crystal counterparts that suffer from a low capacity delivery. The zero-strain property is evidenced by substantial characterizations including ex/in situ transmission electron microscopy and mechanical simulations. The Si NDsâMDN exhibits superior cycling stability and high reversible capacity (1327 mAh g-1 at 0.1 A g-1 after 100 cycles) in half-cells and high energy density (366 Wh kg-1 after 300 cycles) in a full cell. This study reports a new catalog of zero-strain electrode material with significantly improved capacity beyond the traditional single-crystal zero-strain materials.
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The 3D (three-dimensional) oriented nanosheet array FeNi2P electrocatalyst grown on carbon cloth (FeNi2P/CC) is explored in this work. This unique 3D oriented nanosheet array structure can expose more catalytic active sites, promote the penetration of electrolyte solution on the catalyst surface, and facilitate the transfer of ions, thus speeding up the kinetic process of Hydrogen evolution reaction (HER) and Oxygen evolution reaction (OER). At the current densities of 10 mA/cm2 in 1 M KOH solution, the HER overpotential (71 mV) of the FeNi2P/CC self-supporting electrode is very close to that of noble metal HER catalyst of 20% Pt/C (54 mV), and its OER overpotential (210 mV) is 34% lower than that of the precious metal OER catalyst of RuO2 (318 mV), demonstrating the excellent electrocatalytic performance of the FeNi2P/CC catalyst. Moreover, the cell voltage for full water splitting (at 10 mA/cm2 current densities) of the FeNi2P/CC bifunctional electrode cell is 1.52 V, which is 3.8% lower than that of the full noble-metal electrode reference cell (RuO2 || Pt/C, 1.58 V), suggesting that this FeNi2P/CC bifunctional catalyst is likely to replace precious metals to reduce the costs in full water splitting application. According to density functional theory (DFT) calculation results, the introduction of iron atom can change the electronic structure of the Ni2P, so it can reduce the adsorption energy of hydrogen and oxygen, and facilitate the adsorption and desorption of hydrogen and oxygen on the surface of the catalyst, improving its performance of HER and OER.
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The exploration for low-cost bifunctional materials for highly efficient overall water splitting has drawn profound research attention. Here, we present a facile preparation of Mo-P dual-doped Co/oxygen-deficient Co3O4 core-shell nanorods as a highly efficient electrocatalyst. In this strategy, oxygen vacancies are first generated in Co3O4 nanorods by lithium reduction at room temperature, which endows the materials with bifunctional characteristics of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). A Co layer doped with Mo and P is further deposited on the surface of the Co3O4-x nanorods to enhance the electrocatalytic hydrolysis performance. As a result, the overpotentials of HER and OER are only 281 and 418 mV at a high current density of 100 mA cm-2 in 1.0 M KOH, respectively. An overall water electrolytic cell using CoMoP@Co3O4-x nanorods as both electrodes can reach 10 mA cm-2 at 1.614 V with outstanding durability. The improvement is realized by the synergistic effect of oxygen vacancies, Mo/P doping, and core-shell heterostructures for modulating the electronic structure and producing more active sites, which suggests a promising method for developing cost-effective and stable electrocatalysts.
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The Li metal anode is considered one of the most potential anodes due to its highest theoretical specific capacity and the lowest redox potential. However, the scalable preparation of safe Li anodes remains a challenge. In the present study, a LiF-rich protection layer has been developed using self-driven chemical reactions between the Li3xLa2/3-xTiO3/polyvinylidene fluoride/dimethylacetamide (LLTO/PVDF/DMAc) solution and the Li metal. After coating the LLTO/PVDF/DMAc solution to Li foil, PVDF reacted with Li spontaneously to form LiF, and the accompanying Ti4+ ions (in LLTO) were reduced to Ti3+ to form a mixed ionic and electronic conductor LixLLTO. The protective layer can redistribute the Li-ion transport, regulate the even Li deposition, and inhibit the Li dendrite growth. When paired with LiFePO4, NCM811, and S cathodes, the batteries have demonstrated excellent capacity retention and cycling stability. More importantly, a volumetric energy density of 478 Wh L-1 and 78% capacity retention after 310 cycles have been achieved by using a S/LixLLTO-Li pouch cell. This work provides a feasible avenue to provide large-scale preparation of safe Li anodes for the next-generation pouch-type Li-S batteries as ideal power sources for flexible electronic devices.
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High-entropy alloys (HEAs), as an emerging class of materials, have pointed a pathway in developing alloys with interesting property combinations. Although they are not exempted from the strength-ductility trade-off, they present a standing chance in overcoming this challenge. Here, we report results for a precipitation-strengthening strategy, by tuning composition to design a CoNiV-based face-centered cubic/B2 duplex HEA. This alloy sustains ultrahigh gigapascal-level tensile yield strengths and excellent ductility from cryogenic to elevated temperatures. The highest specific yield strength (~150.2 MPa·cm3/g) among reported ductile HEAs is obtained. The ability of the alloy presented here to sustain this excellent strength-ductility synergy over a wide temperature range is aided by multiple deformation mechanisms i.e., twins, stacking faults, dynamic strain aging, and dynamic recrystallization. Our results open the avenue for designing precipitation-strengthened lightweight HEAs with advanced strength-ductility combinations over a wide service temperature range.
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TiO2 nanostructures have been one of the most explored metal oxides photocatalysts to apply for environmental remediation. However, its wide band gap results in the underutilization of sunlight for degradation of pollutants. In order to overcome this handicap, the synthesis of TiO2-based composite has brought extraordinary materials. In this study, we design and prepare TiO2/Nb2O5 heterostructures with different molar ratios by using peroxotitanium and peroxoniobium complex as precursors in aqueous solution. The TiO2 exists in the form of anatase while Nb2O5 is amorphous in the composite, leading to a special crystalline TiO2/amorphous Nb2O5 heterostructures. In particular, Nb element is also doped and Ti3+ ions are formed in the TiO2 lattice, leading to a reduced band gap. The unique TiO2/0.25Nb2O5 (Ti:Nb = 2:1) heterostructures can effectively suppress the recombination of photogenerated electrons and holes, and facilitate the charge transfer, resulting in the optimum photocatalytic performance. The nitrogen oxide removal efficiency by TiO2/0.25Nb2O5 is 77.23% in visible light, which is 3.8-folds and 7.0-folds higher than pure TiO2 and Nb2O5. Photocatalytic degradation of acetaminophen by TiO2/0.25Nb2O5 is 90.6% in visible light, which is approximately 2.5-folds higher than pure TiO2 and Nb2O5.
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Acetaminofen , Nióbio , Catálise , Óxidos de Nitrogênio , TitânioRESUMO
B atoms and cyano groups co-doped graphite carbon nitride with nitrogen vacancies (VN-BC-CN) was explored via one-step in-situ route. A series of comprehensive experiments confirmed that B atoms and cyano groups had been doped into the framework of graphite carbon nitride, forming VN-BC-CN catalyst sample with a large number of nitrogen-vacancy defects. As electron acceptors, B and cyano groups could be used as active sites for nitrogen conversion. The defect level caused by nitrogen vacancy led to red shift of the light absorption edge, which resulted in higher separation efficiency of photo-induced carriers and faster transfer rate of photo-induced electrons for the VN-BC-CN catalyst. This VN-BC-CN catalyst had good photocatalytic nitrogen fixation performance in the ultrapure water without any hole-scavengers. The nitrogen photofixation rate of VN-BC-CN (115.53 µmol g-1 h-1) was 25.5 times that of pure carbon nitride (GCN, 4.53 µmol g-1 h-1). Moreover, NH4+ generation rate hardly decreased after 10 h reaction, and the NH4+ generation rate could reach 79.56 µmol g-1 h-1 in the fifth cycle, showing the good photocatalytic stability of the VN-BC-CN catalyst.
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Fixação de Nitrogênio , Água , Catálise , Luz , NitrogênioRESUMO
The genetic improvement of nitrogen use efficiency (NUE) of crops is vital for grain productivity and sustainable agriculture. However, the regulatory mechanism of NUE remains largely elusive. Here, we report that the rice Grain number, plant height, and heading date7 (Ghd7) gene genetically acts upstream of ABC1 REPRESSOR1 (ARE1), a negative regulator of NUE, to positively regulate nitrogen utilization. As a transcriptional repressor, Ghd7 directly binds to two Evening Element-like motifs in the promoter and intron 1 of ARE1, likely in a cooperative manner, to repress its expression. Ghd7 and ARE1 display diurnal expression patterns in an inverse oscillation manner, mirroring a regulatory scheme based on these two loci. Analysis of a panel of 2656 rice varieties suggests that the elite alleles of Ghd7 and ARE1 have undergone diversifying selection during breeding. Moreover, the allelic distribution of Ghd7 and ARE1 is associated with the soil nitrogen deposition rate in East Asia and South Asia. Remarkably, the combination of the Ghd7 and ARE1 elite alleles substantially improves NUE and yield performance under nitrogen-limiting conditions. Collectively, these results define a Ghd7-ARE1-based regulatory mechanism of nitrogen utilization, providing useful targets for genetic improvement of rice NUE.
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Nitrogênio/metabolismo , Oryza/genética , Proteínas de Plantas/genética , Sementes/crescimento & desenvolvimento , Fatores de Transcrição/metabolismo , Alelos , Grão Comestível/química , Grão Comestível/genética , Grão Comestível/metabolismo , Regulação da Expressão Gênica de Plantas , Oryza/química , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Regiões Promotoras Genéticas , Sementes/genética , Sementes/metabolismoRESUMO
Sn@Graphene composites as anode materials in Lithium-ion batteries have attracted intensive interest due to the inherent high capacity. On the other side, the high atomic ratio (Li4.4Sn) induces the pulverization of the electrode with cycling. Thus, suppressing pulverization by designing the structure of the materials is an essential key for improving cyclability. Applying the nanotechnologies such as electrospinning, soft/hard nano template strategy, surface modification, multi-step chemical vapor deposition (CVD), and so on has demonstrated the huge advantage on this aspect. These strategies are generally used for homogeneous dispersing Sn nanomaterials in graphene matrix or constructing the voids in the inner of the materials to obtain the mechanical buffer effect. Unfortunately, these processes induce huge energy consumption and complicated operation. To solve the issue, new nanotechnology for the composites by the bottom-up strategy (Organic Molecule Confinement Reaction (OMCR)) was shown in this report. A 3D organic nanoframes was synthesized as a graphene precursor by low energy nano emulsification and photopolymerization. SnO2 nanoparticles@3D organic nanoframes as the composites precursor were in-situ formed in the hydrothermal reaction. After the redox process by the calcination, the Sn nanoparticles with nanovoids (~100 nm, uniform size) were homogeneously dispersed in a Two-Dimensional Laminar Matrix of graphene nanosheets (2DLMG) by the in-situ patterning and confinement effect from the 3D organic nanoframes. The pulverization and crack of the composites were effectively suppressed, which was proved by the electrochemical testing. The Sn nanoparticles@2DLMG not delivered just the high cyclability during 200 cycles, but also firstly achieved a high specific capacity (539 mAh g-1) at the low loading Sn (19.58 wt%).