/Tag: Energy

Influence of temperature on the displacement threshold energy in graphene. (arXiv:1811.04011v1 [cond-mat.mtrl-sci])

2018-11-12T02:29:26+00:00November 12th, 2018|Categories: Publications|Tags: , |

The atomic structure of nanomaterials is often studied using transmission electron microscopy. In addition to image formation, the energetic electrons may also cause damage while impinging on the sample. In a good conductor such as graphene the damage is limited to the knock-on process caused by elastic electron-nucleus collisions. This process is determined by the kinetic energy an atom needs to be sputtered, ie, its displacement threshold energy. This is typically assumed to have a fixed value for all electron impacts on equivalent atoms within a crystal. Here we show using density functional tight-binding simulations that the displacement threshold energy is affected by the thermal perturbation of the atoms from their equilibrium positions. We show that this can be accounted for in the estimation of the displacement cross section by replacing the constant threshold value with a distribution. The improved model better describes previous precision measurements of graphene knock-on damage, and should be considered also for other low-dimensional materials.

Published in: "arXiv Material Science".

3D 3C‐SiC/Graphene Hybrid Nanolaminate Films for High‐Performance Supercapacitors

2018-11-11T14:34:28+00:00November 11th, 2018|Categories: Publications|Tags: , |

High‐performance electrical double layer capacitors and pseudocapacitors are fabricated and compared using vertically aligned 3C‐SiC/graphene nanolaminate films in both aqueous and organic solutions. Their big and stable capacitances and high power and energy densities result from a 3D alternating structure of 3C‐SiC and graphene layers inside these chemical vapor deposited films, their high surface areas, and excellent conductivity. Abstract High‐performance supercapacitors feature big and stable capacitances and high power and energy densities. To fabricate high‐performance supercapacitors, 3D 3C‐SiC/graphene hybrid nanolaminate films are grown via a microwave plasma‐assisted chemical vapor deposition technique. Such films consist of 3D alternating structures of vertically aligned 3C‐SiC and graphene layers, leading to high surface areas and excellent conductivity. They are further applied as the capacitor electrodes to construct electrical double layer capacitors (EDLCs) and pseudocapacitors (PCs) in both aqueous and organic solutions. The capacitance for an EDLC in aqueous solutions is up to 549.9 µF cm−2, more than 100 times higher than that of an epitaxial 3C‐SiC film. In organic solutions, it is 297.3 µF cm−2. The pseudocapacitance in redox‐active species (0.05 Fe(CN)63−/4−) contained aqueous solutions is as high as 62.2 mF cm−2. The capacitance remains at 98% of the initial value after 2500 charging/discharging cycles, indicating excellent cyclic stability. In redox‐active species (0.01 m ferrocene) contained organic solutions, it is 16.6 mF cm−2. Energy and power densities of a PC in aqueous solution are 11.6 W h kg−1 and 5.1 kW kg−1, respectively. These vertically aligned 3C‐SiC/graphene hybrid nanolaminate films are thus promising

Published in: "Small".

Microstructural Degradation of Ni‐Rich Li[NixCoyMn1−x−y]O2 Cathodes During Accelerated Calendar Aging

2018-11-11T14:34:26+00:00November 11th, 2018|Categories: Publications|Tags: |

Microstructural degradation of Ni‐rich Li[Nix Coy Mn1–x–y]O2 cathode materials during calendar aging is reported. Because of parasitic reactions, microcracks develop and remain across the entire secondary particle, even after discharging. An NiO‐like phase rock‐salt structure accumulates and exfoliates from the main particles, continuously exposing fresh surfaces. This phenomenon reflects in the electrochemical performance including the discharge capacity and the voltage profile. Abstract Because electric vehicles (EVs) are used intermittently with long resting periods in the fully charged state before driving, calendar aging behavior is an important criterion for the application of Li‐ion batteries used in EVs. In this work, Ni‐rich Li[Ni xCo yMn1 −x−y]O2 (x = 0.8 and 0.9) cathode materials with high energy densities, but low cycling stabilities are investigated to characterize their microstructural degradation during accelerated calendar aging. Although the particles seem to maintain their crystal structures and morphologies, the microcracks which develop during calendar aging remain even in the fully discharged state. An NiO‐like phase rock‐salt structure of tens of nanometers in thickness accumulates on the surfaces of the primary particles through parasitic reactions with the electrolyte. In addition, the passive layer of this rock‐salt structure near the microcracks is gradually exfoliated from the primary particles, exposing fresh surfaces containing Ni4+ to the electrolyte. Interestingly, the interior primary particles near the microcracks have deteriorated more severely than the outer particles. The microstructural degradation is worsened with increasing Ni contents in the cathode materials, directly affecting electrochemical performances such as the reversible capacities and voltage profiles.

Published in: "Small".

Promise and Challenge of Phosphorus in Science, Technology, and Application

2018-11-11T04:33:02+00:00November 11th, 2018|Categories: Publications|Tags: , |

The synthesis, properties, functionalization, and applications of phosphorus are reviewed to reveal the challenges and opportunities facing present and future research on phosphorus‐based functional materials. The topological constructions of various phosphorus‐based functional materials are an encouraging prospect in the rapid development of nanotechnology. Abstract Tremendous progress has been made in scientific research and application of phosphorus allotropes and their hybrid materials in recent decades. In particular, nanomaterial design has emerged as a promising solution to tackle many fundamental problems in conventional materials. This review discusses phosphorus‐based functional materials from the perspective of topological structures, which have several advantages such as good chemical stability, high surface areas, adjustable particle sizes and compositions, as well as various functionalities that enable a good performance in energy storage and conversion as well as other applications. Then, the progress on these functional materials for application in batteries, supercapacitors, catalysis, field‐effect transistors, optoelectronics, flexible electronics, sensors, biomedicine, etc., is discussed and summarized as well. Special attention is given to the research efforts to overcome the inherent shortcomings faced by red/black phosphorus. The aim is to elucidate the relationship between the phosphorus‐based topological structures and their performance. Finally, this review casts an insightful outlook on the future direction of the phosphorus‐based materials in nanotechnology.

Published in: "Advanced Functional Materials".

Ultramicroporous Carbons Puzzled by Graphene Quantum Dots: Integrated High Gravimetric, Volumetric, and Areal Capacitances for Supercapacitors

2018-11-11T04:33:00+00:00November 11th, 2018|Categories: Publications|Tags: , |

Ultramicroporous carbon with both high specific surface area (1730 m2 g−1) and packing density (0.97 g cm−3), constructed using graphene quantum dots as building units, shows integrated high gravimetric/volumetric/areal capacitances as well as excellent rate performance and cycling stability. Abstract Porous carbons integrated with high gravimetric/volumetric/areal capacitances, especially at high mass loadings (>10 mg cm−2), are important for practical applications in supercapacitors. Here, a strategy is developed for the synthesis of ultramicroporous carbons puzzled by graphene quantum dots as the building units through chemical welding and in situ activation. The resulted carbon has unique ultramicroporous structure (≈0.5 nm) with both high surface area (1730 m2 g−1) and packing density (0.97 g cm−3), providing high gravimetric and volumetric capacitances of 270 F g−1 and 262 F cm−3 at 1 A g−1, respectively. More importantly, such carbon achieves an ultrahigh areal capacitance of 5.70 F cm−2 with a high mass loading of 25 mg cm−2 at 1 A g−1, which is one of the best among the previously reported porous carbons. Furthermore, a two‐electrode supercapacitor exhibits an ultrahigh areal capacitance of 3 F cm−2 at 0.5 A g−1, rapid charge–discharge ability, and long lifespan. This work paves an avenue for developing advanced porous carbons with integrated capacitive performances for supercapacitors.

Published in: "Advanced Functional Materials".

Graphene‐Sensitized Perovskite Oxide Monolayer Nanosheets for Efficient Photocatalytic Reaction

2018-11-11T04:32:54+00:00November 11th, 2018|Categories: Publications|Tags: , , |

Ca2Nb3O10 monolayer nanosheet/reduced graphene oxide (RGO) (CNOMS/RGO) 2D–2D nanohybrids with much enhanced photocatalytic H2 production and tetracycline hydrochloride degradation activities are successfully synthesized. Integrating the experiment data with density functional theory calculation, it is demonstrated that RGO acts as an excellent photosensitizer to boost the visible‐light–harvesting of monolayer CNO nanosheets in solar‐energy conversion. Abstract Efficient visible light harvesting and fast charge transfer are of high importance for solar‐energy conversion over semiconducting metal oxide photocatalysts. Here, a proof‐of‐concept strategy is developed to enable visible‐light photocatalytic activity of wide bandgap Ca2Nb3O10 monolayer nanosheet by incorporation of reduced graphene oxide (RGO) nanosheet as a photosensitizer. The Ca2Nb3O10 monolayer nanosheet/RGO 2D–2D nanohybrids exhibit largely elevated performance in photocatalytic H2 evolution with a H2 production rate of 820.76 µmol h−1 g−1 and tetracycline hydrochloride degradation reactions under the visible light irradiation. The combined experimental and theoretical results demonstrate that the electrons generated from the photoexcited RGO transfer to the Ca2Nb3O10 monolayer nanosheet and then participate in the photocatalytic reactions. The constructed RGO sensitized monolayer perovskite photocatalyst nanohybrids are demonstrated as an efficient photosensitizer for enhancing visible light harvesting of wide bandgap semiconductor in solar‐energy conversion, and elaborated in details of the charge transfer process of this type of nanohybrid photocatalyst.

Published in: "Advanced Functional Materials".

Bioinspired Micro/Nanofluidic Ion Transport Channels for Organic Cathodes in High‐Rate and Ultrastable Lithium/Sodium‐Ion Batteries

2018-11-11T04:32:52+00:00November 11th, 2018|Categories: Publications|Tags: , , |

Inspired by the fast permeation of ions within the protein ion channels on cell membranes, a flexible sandwich‐structured 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA)/reduced graphene oxide (RGO)/carbon nanotube (CNT) (PTCDA/RGO/CNT) film with bioinspired three‐dimensional multilayered micro/nanochannels is designed for lithium and sodium ion batteries. Because of the unique structural features, the PTCDA/RGO/CNT electrode exhibits particularly excellent lithium/sodium storage performance and cyclic stability. Abstract Conjugated carbonyl compounds are considered as ideal substitutes for traditional inorganic electrodes in lithium/sodium ion batteries (LIBs/SIBs) due to their excellent redox reversibility and structural tunability. Here, a flexible sandwich‐structured 3,4,9,10‐perylenetetracarboxylic dianhydride (PTCDA)/reduced graphene oxide (RGO)/carbon nanotube (CNT) (PTCDA/RGO/CNT) composite film with bioinspired micro/nanofluidic ion transport channels and interconnected porous conductive frameworks is designed and obtained by vacuum‐filtration and heating methods for LIB/SIB applications. The PTCDA/RGO/CNT electrode with robust mechanical deformability exhibits high diffusion coefficients of Li+/Na+ and low Warburg coefficients. Thus, desirable electrochemical performances with high capacities of 131 and 126 mA h g−1 at 10 mA g−1, and ultralong cycling stability with over 99% capacity retention after 500 cycles at 200 mA g−1 are achieved for LIBs and SIBs, respectively. In particular, Li/Na‐ion full cells consisting of lithiated or sodiated electrospun carbon nanofiber anode and PTCDA/RGO/CNT‐based cathode are developed to exhibit high energy densities of 132.6 and 104.4 W h kg−1 at the power densities of 340 and 288 W kg−1 for LIBs and SIBs, respectively. The advantageous features demonstrated by constructing bioinspired micro/nanofluidic channels may provide a new pathway toward the design of next‐generation wearable energy

Published in: "Advanced Functional Materials".

Pseudocapacitance Induced Uniform Plating/Stripping of Li Metal Anode in Vertical Graphene Nanowalls

2018-11-11T04:32:46+00:00November 11th, 2018|Categories: Publications|Tags: , |

A pseudocapacitive surface of vertical graphene nanowalls is investigated to regulate Li plating/stripping behaviors. Very fast Li+ ion transfer and uniform Li+ adsorption/desorption are demonstrated as significant benefits by using such an advanced surface structure for stable Li metal cycling even at a high depth of discharge of 50%. Abstract Unevenly distributed dendrite growth is usually viewed as a consequence to the diffusion‐limited interface instability during electrodeposition, leading to one of the most serious obstacles hindering the application of high‐capacity lithium (Li) metal anodes. Herein, a fundamental issue of modifying Li plating behavior using a structure of 3D vertical graphene nanowalls on nickel (Ni) foam (VGN/Ni) is investigated. Such a structure exhibits a significant pseudocapacitive interfacial feature, greatly improving the Li+ ion transfer kinetic through the structure, and exhibiting uniform Li plating/stripping for stable Li metal cycling even at a high depth of discharge of 50%. Based on such a structure, high Coulombic efficiencies ≈97% and 99% can be obtained in carbonate and ether electrolyte over long‐term cycling. The symmetrical cell based on the VGN/[email protected] composite anodes can afford a stable cycling of 2000 h with low voltage hysteresis of 30 mV. Full cell system using VGN/[email protected] composite anode and LiFePO4 cathode is also proved, with high capacity retention of 89.4% at the 1000th cycle. The pseudocapacitance induced benefits, which have not yet been elucidated for Li metal anodes, can conduct to underlying strategy in designing stable Li metal host for high‐energy‐density batteries.

Published in: "Advanced Functional Materials".

A Multifunctional Silly‐Putty Nanocomposite Spontaneously Repairs Cathode Composite for Advanced Li−S Batteries

2018-11-11T04:32:44+00:00November 11th, 2018|Categories: Publications|Tags: , , |

Self‐healing conductive polymer reduced graphene oxide–Silly Putty enables effective suppression of “shuttle effects” while spontaneously forming all‐around conductive protecting layer on the surface of the cathode and repairs the mechanical/structure damages of the cathode in Li−S batteries during cycling is reported. As a result, the G‐SP added cell delivers a capacity of 586 mAh g−1 after 1000 cycles. Abstract Although lithium–sulfur batteries have been regarded as one of the most promising candidates for high efficient energy storage devices, however, their practical application are still hindered by the notorious “shuttle effect” and instability of cathode structure during cycling. In this work, conductive reduced graphene oxides nanosheets added–putty (rGO–putty ) adaptive functional interlayer is designed to effectively suppress the diffusion of polysulfides while simultaneously promoted the dynamic protection of the whole cathode structure during cycling. Consequently, largely suppressed polysulfides diffusion combined with the greatly enhanced cathode stability is achieved while the all‐around conductive protecting layer is formed benefited from the viscoelasticity property of rGO–putty. As a result, a capacity of 586 mAh g−1 is demonstrated after long‐cycling term of 1000 cycles and high cycling stability of only 0.03% capacity decay per cycle is exhibited. The largely enhanced electrochemical performance suggests the important role of the rGO–putty in suppressing the “shuttle effect” and maintaining the integrity of the cathode material.

Published in: "Advanced Functional Materials".

Carbon Nitride Nanofibres with Exceptional Lithium Storage Capacity: From Theoretical Prediction to Experimental Implementation

2018-11-11T04:32:41+00:00November 11th, 2018|Categories: Publications|Tags: , |

A g‐C3N4 fibre structure with edges and low graphitic nitrogen content is developed as an anode material for lithium‐ion batteries. The g‐C3N4 fibre structure delivered an ultrahigh specific capacity of 181.7 mAh g−1 after 200 cycles at 0.5 C and 138.6 mAh g−1 at 10C with an exceptional long life of 5000 cycles. Abstract Graphitic carbon nitride nanosheet (i.e., g‐C3N4) is identified as a suitable graphene analogue due to its high theoretical capacity, wider and vacant structure, and easy synthesis method. Currently, g‐C3N4 nanosheet has limited application in lithium‐ion batteries (LIBs) which is mainly due to the lack of effective intercalation/deintercalation reaction sites, the high binding energy of the Li to the nanosheet, and insufficient conductivity and stability. Density functional theory calculation predicts that the edges of g‐C3N4 fibre have a suitable adsorption energy and bestow a balanced adsorption force and desorption freedom to Li. In order to verify this prediction, g‐C3N4 nanofibre is synthesized with the edges and pores, as well as higher pyridinic nitrogen content, using a simple polymerization/polycondensation method. The as‐prepared g‐C3N4 fibre delivers a remarkable specific capacity of 181.7 mAh g−1, as well as extraordinary stability and power density. At a high rate of 10C, the g‐C3N4 fibre still has a specific capacity of 138.6 mAh g−1 even after 5000 cycles, being the best‐performing g‐C3N4 electrode so far in literature. This work is exemplary in combining theoretical computing and experimental techniques in designing the next generation of electroactive materials for LIBs.

Published in: "Advanced Functional Materials".

3D‐Printed Graphene Oxide Framework with Thermal Shock Synthesized Nanoparticles for Li‐CO2 Batteries

2018-11-11T04:32:30+00:00November 11th, 2018|Categories: Publications|Tags: , , |

An ultrathick electrode (≈0.4 mm) with ultrafine Ni nanoparticles (≈5 nm) anchored on a 3D reduced graphene oxide framework is designed as cathode for Li‐CO2 batteries via 3D printing technique and thermal shock treatment (1900 K for 54 ms). The electrode exhibits low overpotential, long cycling life, good rate capability, and high areal capacity for Li‐CO2 batteries. Abstract Li‐CO2 batteries have emerged as a promising energy storage technology due to their high theoretical energy density. A thick electrode design is an effective approach for further increasing the energy density on device level by decreasing the weight and volume ratios of inactive materials. Exploring and designing novel thick electrodes with high catalytic activity toward reversible reaction between lithium and carbon dioxide are key challenges to achieve a low charge overpotential, long cycling stability, and high rate performance. Herein, an ultrathick electrode (≈0.4 mm) design for Li‐CO2 batteries by anchoring ultrafine Ni nanoparticles (≈5 nm) on a 3D‐printed reduced graphene oxide framework via thermal shock (1900 K for 54 ms) is demonstrated. The cathode displays low overpotential of 1.05 V at 100 mA g−1, high cycling stability of over 100 cycles, and good rate capability (up to 1000 mA g−1). In particular, a high areal capacity of 14.6 mA h cm−2 can be achieved due to the thick electrode design and uniform distribution of ultrafine catalyst nanoparticles. The strategy of combining an advanced 3D printing technique with fast thermal shock represents a promising direction toward thick electrode design in energy storage

Published in: "Advanced Functional Materials".

Thermally Conductive Phase Change Composites Featuring Anisotropic Graphene Aerogels for Real‐Time and Fast‐Charging Solar‐Thermal Energy Conversion

2018-11-11T04:32:21+00:00November 11th, 2018|Categories: Publications|Tags: , , |

Anisotropic and high‐quality graphene aerogels are fabricated by directional‐freezing of polyamic acid salt/graphene oxide slurries, followed by freeze‐drying, imidization, and graphitization. A phase change composite derived from the aerogel exhibits both high longitudinal thermal conductivity of ≈8.87 W m−1 K−1 and excellent latent heat retention of 98.7% with satisfactory stability, and is suitable for real‐time and fast solar‐thermal energy conversion. Abstract Phase change materials (PCMs) have triggered considerable attention as candidates for solar‐thermal energy conversion. However, their intrinsic low thermal conductivity prevents the rapid spreading of heat into the interior of the PCM, causing low efficiencies in energy storage/release. Herein, anisotropic and lightweight high‐quality graphene aerogels are developed by directionally freezing aqueous suspensions of polyamic acid salt and graphene oxide to form vertically aligned monoliths, followed by freeze‐drying, imidization at 300 °C and graphitization at 2800 °C. After impregnating with paraffin wax, the resultant phase change composite (PCC) exhibits a high transversal thermal conductivity of 2.68 W m−1 K−1 and an even higher longitudinal thermal conductivity of 8.87 W m−1 K−1 with an exceptional latent heat retention of 98.7%. When subjected to solar radiation, solar energy is converted to heat at the exposed surface of the PCC. As a result of the PCC’s high thermal conductivity in the thickness direction, heat can spread readily into the interior of the PCC enabling a small temperature gradient of <3.0 K cm−1 and a fast charging feature. These results demonstrate the potential for real‐time and fast‐charging solar‐thermal energy conversion using phase change

Published in: "Advanced Functional Materials".

Surface Modulation of Hierarchical MoS2 Nanosheets by Ni Single Atoms for Enhanced Electrocatalytic Hydrogen Evolution

2018-11-11T04:32:16+00:00November 11th, 2018|Categories: Publications|Tags: , |

Surface modulation at the atomic level has been an important approach for boosting the performance of electrocatalysts. Here, a combined theoretical and experimental study on Ni atom decorated hierarchical MoS2 nanosheets supported on a multichannel carbon matrix (MCM) is presented. The obtained hybrid [email protected]–Ni electrocatalyst with activated S sites exhibits high performance in electrocatalytic hydrogen evolution. Abstract Surface modulation at the atomic level is an important approach for tuning surface chemistry and boosting the catalytic performance. Here, a surface modulation strategy is demonstrated through the decoration of isolated Ni atoms onto the basal plane of hierarchical MoS2 nanosheets supported on multichannel carbon nanofibers for boosted hydrogen evolution activity. X‐ray absorption fine structure investigation and density functional theory (DFT) calculation reveal that the MoS2 surface decorated with isolated Ni atoms displays highly strengthened H binding. Benefiting from the unique tubular structure and basal plane modulation, the newly developed MoS2 catalyst exhibits excellent hydrogen evolution activity and stability. This single‐atom modification strategy opens up new avenues for tuning the intrinsic catalytic activity toward electrocatalytic water splitting and other energy‐related processes.

Published in: "Advanced Functional Materials".

Architectured Leaf‐Inspired Ni0.33Co0.66S2/Graphene Aerogels via 3D Printing for High‐Performance Energy Storage

2018-11-11T04:32:14+00:00November 11th, 2018|Categories: Publications|Tags: , , |

A shape‐programmable Ni0.33Co0.66S2/graphene aerogel is 3D printed (3DP‐NCS/G) to mimic the mass transfer process of natural leaves. A hybrid ink is developed for components regulation and shape design. The interconnected networks and massive exposed edge sites of the 3DP‐NCS/G aerogels contribute to enhanced electrochemical performances. The device delivers competitive areal energy/power densities at practical levels of mass loading. Abstract The construction of high‐performance electrodes with sufficient active sites and interconnected networks for rapid electron/ions transport is challengeable for energy storage devices. Inspired by natural leaves, a facile 3D‐printing strategy for constructing architected Ni0.33Co0.66S2/graphene (3DP‐NCS/G) aerogels to mimic the analogous mass transfer process toward superior electrochemical performances is demonstrated. The key step is to develop hybrid inks with printability and homogeneity by introducing sodium alginate into graphene oxide solutions to boost viscoelastic responses and adopting a new developed precursor Ni0.33Co0.66(OH)2·xH2O with ultrafine and high stable features. Benefiting from high‐speed channels for electron/ion transport provided by the interconnected graphene frameworks and massive exposed edge sites provided by the uniformly dispersed Ni0.33Co0.66S2 nanoparticles, the 3DP‐NCS/G electrode exhibits capacities of 217.6 mAh g−1 at 1 A g−1 and 164.6 mAh g−1 at 10 A g−1. Furthermore, a hybrid device is demonstrated for the first time with both electrodes manufactured by 3D‐printing technique, which delivers excellent areal energy/power densities with values comparable to those of commercial devices, even at a practical level of electrode mass loading (17.86 mg cm−2). This work offers a versatile strategy for integrating various functional nanomaterials with programmable architectures toward

Published in: "Advanced Functional Materials".

Pseudomorphic Transformation of Interpenetrated Prussian Blue Analogs into Defective Nickel Iron Selenides for Enhanced Electrochemical and Photo‐Electrochemical Water Splitting

2018-11-11T00:33:06+00:00November 10th, 2018|Categories: Publications|Tags: |

A defect‐rich porous selenide‐based framework is obtained from an interpenetrated Prussian blue analog network. The resulting structure displays an interconnected porous conductive network at the microscopic level and exposes excess reactive crystal boundary defects in the form of unsaturated atoms at the edges and interfaces at the atomic level. It delivers highly reactive and durable photo(electro)chemical energy conversion functionalities. Abstract A significant methodology gap remains in the construction of advanced electrocatalysts, which has collaborative defective functionalities and structural coherence that maximizes electrochemical redox activity, electrical conductivity, and mass transport characteristics. Here, a coordinative self‐templated pseudomorphic transformation of an interpenetrated metal organic compound network is conceptualized into a defect‐rich porous framework that delivers highly reactive and durable photo(electro)chemical energy conversion functionalities. The coordinative‐template approach enables previously inaccessible synthesis routes to rationally accomplish an interconnected porous conductive network at the microscopic level, while exposing copious unsaturated reactive sites at the atomic level without electronic or structural integrity trade‐offs. Consequently, porous framework, interconnected motifs, and engineered defects endow remarkable electrocatalytic hydrogen evolution reaction and oxygen evolution reaction activity due to intrinsically improved turnover frequency, electrochemical surface area, and charge transfer. Moreover, when the hybrid is coupled with a silicon photocathode for solar‐driven water splitting, it enables photon assisted redox reactions, improved charge separation, and enhanced carrier transport via the built‐in heterojunction and additive co‐catalyst functionality, leading to a promising photo(electro)chemical hydrogen generation performance. This work signifies a viable and generic approach to prepare other functional interconnected metal organic coordinated compounds, which can

Published in: "Advanced Energy Materials".

Promoted Glycerol Oxidation Reaction in an Interface‐Confined Hierarchically Structured Catalyst

2018-11-10T22:35:06+00:00November 10th, 2018|Categories: Publications|Tags: , |

The confinement of Pt nanosheets is realized in a vertically erected graphene array with hierarchically porous architecture to address the mass‐diffusion limitation in interface‐confined catalysis. Such a confined 3D catalyst exhibits a much stronger oxidation and CC bond cleaving ability for the glycerol oxidation reaction, leading to a superior mass activity and selectivity toward C1 products than commercial Pt/C catalysts. Abstract Confined catalysis in a 2D system is of particular interest owing to the facet control of the catalysts and the anisotropic kinetics of reactants, which suppress side reactions and improve selectivity. Here, a 2D‐confined system consisting of intercalated Pt nanosheets within few‐layered graphene is demonstrated. The strong metal–substrate interaction between the Pt nanosheets and the graphene leads to the quasi‐2D growth of Pt with a unique (100)/(111)/(100) faceted structure, thus providing excellent catalytic activity and selectivity toward one‐carbon (C1) products for the glycerol oxidation reaction. A hierarchically porous graphene architecture, grown on carbon cloth, is used to fabricate the confined catalyst bed in order to enhance the mass‐diffusion limitation in interface‐confined reactions. Owing to its unique 3D porous structure, this graphene‐confined Pt catalyst exhibits an extraordinary mass activity of 2910 mA mgPt−1 together with a formate selectivity of 79% at 60 °C. This paves the way toward rational designs of heterogeneous catalysts for energy‐related applications.

Published in: "Advanced Materials".

Lithiophilic 3D Nanoporous Nitrogen‐Doped Graphene for Dendrite‐Free and Ultrahigh‐Rate Lithium‐Metal Anodes

2018-11-10T22:34:59+00:00November 10th, 2018|Categories: Publications|Tags: , |

A lithium composite anode is developed by rational combination of 3D nanoporous N‐doped graphene and Li melt. The issues of uncontrolled dendrite growth and infinite volume changes of Li‐metal anodes are simultaneously addressed by the integrated nanoporous Li anode, realizing high cycling stability and ultrafast rate performance at high area capacities. Abstract The key bottlenecks hindering the practical implementations of lithium‐metal anodes in high‐energy‐density rechargeable batteries are the uncontrolled dendrite growth and infinite volume changes during charging and discharging, which lead to short lifespan and catastrophic safety hazards. In principle, these problems can be mitigated or even solved by loading lithium into a high‐surface‐area, conductive, and lithiophilic porous scaffold. However, a suitable material that can synchronously host a large loading amount of lithium and endure a large current density has not been achieved. Here, a lithiophilic 3D nanoporous nitrogen‐doped graphene as the sought‐after scaffold material for lithium anodes is reported. The high surface area, large porosity, and high conductivity of the nanoporous graphene concede not only dendrite‐free stripping/plating but also abundant open space accommodating volume fluctuations of lithium. This ingenious scaffold endows the lithium composite anode with a long‐term cycling stability and ultrahigh rate capability, significantly improving the charge storage performance of high‐energy‐density rechargeable lithium batteries.

Published in: "Advanced Materials".

A Stretchable and Self‐Healing Energy Storage Device Based on Mechanically and Electrically Restorative Liquid‐Metal Particles and Carboxylated Polyurethane Composites

2018-11-10T22:34:49+00:00November 10th, 2018|Categories: Publications|Tags: , |

An elastic conductor composed of nickel flakes, liquid metal, and carboxylated polyurethane is highly conductive, intrinsically stretchable, self‐healing, and electrochemically stable, and it can be utilized in rechargeable soft energy storage applications by means of the complexation of Ga with ligands that shifts the redox potential of Ga(III)/Ga into the stable electrochemical window of an ionic‐liquid electrolyte. Abstract Stretchable and self‐healing (SH) energy storage devices are indispensable elements in energy‐autonomous electronic skin. However, the current collectors are not self‐healable nor intrinsically stretchable, they mostly rely on strain‐accommodating structures that require complex processing, are often limited in stretchability, and suffer from low device packing density and fragility. Here, an SH conductor comprising nickel flakes, eutectic gallium indium particles (EGaInPs), and carboxylated polyurethane (CPU) is presented. An energy storage device is constructed by the two SH electrodes assembled with graphene nanoplatelets sandwiching an ionic‐liquid electrolyte. An excellent electrochemical healability (94% capacity retention upon restretching at 100% after healing from bifurcation) is unveiled, stemming from the complexation modulated redox behavior of EGaIn in the presence of the ligand bis(trifluoromethanesulfonyl)imide, which enhances the reversible Faradaic reaction of Ga. Self‐healing can be achieved where the damaged regions are electrically restored by the flow of liquid metal and mechanically healing activated by the interfacial hydrogen bonding of CPU with an efficiency of 97.5% can be achieved. The SH conductor has an initial conductivity of 2479 S cm−1 that attains a high stretchability with 700% strain, it restores 100% stretchability even after breaking/healing with the electrical

Published in: "Advanced Materials".

Heterostructures Based on 2D Materials: A Versatile Platform for Efficient Catalysis

2018-11-10T22:34:35+00:00November 10th, 2018|Categories: Publications|Tags: , |

The construction of different heterostructures based on 2D materials offers great opportunities for boosting the catalytic activity in electo(photo)chemical reactions. Starting from the theoretical background of the fundamental concepts, the progressive developments in the design and applications of heterostructures based on 2D materials are summarized. Abstract The unique structural and electronic properties of 2D materials, including the metal and metal‐free ones, have prompted intense exploration in the search for new catalysts. The construction of different heterostructures based on 2D materials offers great opportunities for boosting the catalytic activity in electo(photo)chemical reactions. Particularly, the merits resulting from the synergism of the constituent components and the fascinating properties at the interface are tremendously interesting. This scenario has now become the state‐of‐the‐art point in the development of active catalysts for assisting energy conversion reactions including water splitting and CO2 reduction. Here, starting from the theoretical background of the fundamental concepts, the progressive developments in the design and applications of heterostructures based on 2D materials are traced. Furthermore, a personal perspective on the exploration of 2D heterostructures for further potential application in catalysis is offered.

Published in: "Advanced Materials".

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