Electronic Buffer Research Articles

Improved lithium storage performance of urchin-like CuO microspheres by stereotaxically constructed graphene mediating synergistic effect

Urchin-like CuO/stereotaxically constructed graphene (SCG) microspheres are synthesized by one-step hydrothermal method. The size of the obtained urchin-like CuO/SCG microspheres is around 7 µm, which are composed of numerous end-connected nanorods with a diameter of about 80 nm. The existence of SCG inhibits the growth of CuO crystallite and CuO/SCG microspheres compared with the bare CuO microspheres. When directly used as anode materials for LIBs, the bare CuO and CuO/SCG microspheres deliver discharge specific capacities of 486.5 and 770.7 mA h g−1 at 0.1 A g−1 in the 80th cycle, respectively. Even if the current density is as high as 3 A g−1, CuO/SCG microsphere can still deliver a specific discharge capacity of 308.8 mA h g−1. Electrochemical performances of CuO/SCG microsphere are significantly higher than those of the bare CuO, which is attributed that SCG with 3D conductive network can enhance electronic conductivity and buffer volume variation of active material CuO during charge/discharge process.

Ag modified bathocuproine:ZnO nanoparticles electron buffer layer based bifacial inverted-type perovskite solar cells

An Ag modified bathocuproine:ZnO nanoparticles (BCP:ZnO NPs) thin film was used as the buffer layer of inverted-type perovskite solar cells, which increased the bifacial power conversion efficiency from 6.82% to 15.50%. The surface-enhanced Raman scattering and absorbance spectra show that the Ag modified BCP small molecules can effectively passivate the surface oxygen defects of ZnO NPs and thereby increasing the crystallinity, which simultaneously increases the short-circuit current density (J SC ) and fill factor. It is noted that a high incident photon-to-electron conversion efficiency (IPCE) of 92% is achieved at the wavelength of 587 nm due to the constructive interference effect in the multilayer structure, which can be used to explain the high photocurrent generation in a semi-transparent solar cell. In addition, the light intensity-dependent experimental results of the bifacial perovskite solar demonstrates that the hole transportation is better than the electron transportation in the perovskite thin film. This concept can be readily used in the optimization of high-efficiency bifacial perovskite solar cells. • A bifacial PCE of 15.50% is achieved in the bifacial inverted-type MAPbI 3 solar cells. • Ag modified BCP:ZnO NPs thin film is used as the electron buffer layer of MAPbI3 solar cells. • The higher deposition rate of Ag results in the higher FF and PCE. • The asymmetric FF implies that the hole mobility is higher than electron mobility in MAPbI 3 thin films.

Nano SnO2 and Sb2O3 combined with CNTs as a high-capacity lithium storage material

The combination of Sb2O3 or SnO2 with graphene has become a research hotpot in recent years. However, several problems, namely the loading of the active materials, space utilization in composites, and the intrinsic volume expansion of Sb2O3 and SnO2, have yet to be fully resolved. To overcome these disadvantages, in this work Sb2O3/carbon nanotubes (CNTs)/SnO2 composite have been synthesized, in which the CNTs act as a network to ensure the electronic conductivity and buffer of the volume expansion. The SnO2 nanoparticles are aligned by the CNTs and Sb2O3 is dispersed in the voids between them. Space utilization and the loading of the oxides are thereby maximized. Moreover, the resultant composite retains small amount of water or alcohol, which does not affect the cyclic stability, but may have increased the ionic and electronic conductivity, improving the electrochemical performance. A discharge capacity of 910 mAh g−1 after 250 cycles at 100 mA g−1 is realized for Sb2O3/CNT/SnO2. Moreover, the contribution of the pseudocapacitance to the rate discharge capability is obvious, which arises from the different heterointerfaces between Sb2O3/CNTs, CNTs/SnO2 or Sb2O3/SnO2. The homogenous distribution of Sn and Sb in CNTs after cycling leads to a lower discharge voltage, improving the application prospects. Although some collapse and cracks are detected, the CNTs network connects the oxides, ensuring the structural stability and the cyclic stability of Sb2O3/CNT/SnO2. This strategy represents a new concept for the design of multi-component materials for lithium storage.

Pomegranate structured C@pSi/rGO composite as high performance anode materials of lithium-ion batteries

A novel anode materials composed of pomegranate structured carbon @ porous silicon/reduced graphene oxide composite (C@pSi/rGO) was prepared by a facile high temperature pyrolysis and freeze drying technology. In this pomegranate-like composite, porous silicon is equivalent to pomegranate seeds providing sufficient specific capacity, the coated carbon layer is equivalent to pulp which can inhibit the volume expansion and improve electrical conductivity of silicon, and the outermost graphene is equivalent to the inner diaphragm and the outer fruit shell, which can accelerate the ion and electron transport and buffer the volume change of the inner silicon again, so that the cycling stability and rate performance of the material can be effectively improved. As a result, the initial discharge capacity of the C@pSi/rGO composite electrode is 825.7 mAh g−1, after 100 cycles, the reversible capacity of the C@pSi/rGO composite electrode can be maintained at 746 mAh g−1 at a current density of 0.4 A/g with a capacity retention up to 90.4%. However, for the pure porous silicon pSi electrode without carbon coating and graphene recombination, the initial discharge capacity is 769.4 mAh g−1 with almost 0% capacity retention after 30 cycles. Under the dual action of carbon coating and graphene composite, the performance of porous silicon electrode has been significantly improved, which will provide a new idea for the development of high performance silicon carbon anode materials.

Hybrid buffer‐based optical packet switch with negative acknowledgment for multilevel data centers

Abstract In the present scenario, data centers serve many functionalities like storage, transfer of data, supporting web applications, etc. In data centers, various levels of hierarchy different types of switches are required; therefore, multifunctional data centers are desired. This paper discusses a novel design for optical switch which can be placed at various levels of hierarchy. In the proposed design, multifunctionality contention resolution schemes which consider electronic and optical buffering and all-optical negative acknowledgment (AO-NACK) are considered. In buffering technologies, contending packets are stored in either in electronic RAM or in fiber delay lines. In case of the AO-NACK scheme, contending packets are blocked, and a negative acknowledgment is sent back to the transmitting node and blocked packets are retransmitted. For various considered schemes, Monte Carlo simulation have been performed, results in terms of packet loss probability are presented, and it has been found that the performance of optical buffering is much superior to electronic buffering and AO-NACK schemes. It is found that, in the AO-NACK scheme, the numbers of retransmitted packets due to contention blocking are 33,304 which can be reduced to 7, by using a small amount of buffer at each node.

Preparation and superior electrochemical performance of hollow SnO2@C composites as anode materials for high-performance lithium ion batteries

SnO2-based composites have drawn much attention as anode materials for lithium ion batteries due to their high specific capacity. However, they also suffer from rapid capacity fading, which is attributed the poor electronic conductivity and severe volume change. Therefore, it is important to enhance the electronic conductivity and inhibit the volume change at the same time. Based on this theme, herein, hollow SnO2@C composites with perfect structure and high electronic conductivity are synthesized and used as anode materials for lithium ion batteries. The as-prepared hollow SnO2@C composites exhibit high initial specific capacity of 1628 mAh g−1 at 0.1C. The superior electrochemical performance is due to the hollow sphere structure of hollow SnO2@C composites, which could provide novel synthetic method for improving electronic conductivity and buffer the volume change.

Hybrid and optical packet switching supporting different service classes in data center network

Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous optical–electrical–optical conversions in electronic switches, but also a decrease in network latencies due to the cut-through nature of packet transmission. However, it is adversely affected by packet contention, preventing its deployment. Solutions have been proposed to tackle the problem: addition of shared electronic buffers to optical switches (then called hybrid opto-electronic switches), customization of TCP protocols, and use of different service classes of packets with distinct switching criteria. In the context of data center networks, we investigate a combination of said solutions and show that the hybrid switch, compared to the optical switch, boosts the performance of the data center network. Furthermore, we show that introducing a “Reliable” service class improves performance for this class not only in the case of the hybrid switch, but also brings the optical switch to performance levels comparable to that of the hybrid switch, all the while keeping other classes’ performance on the same level.

22% Efficiency Inverted Perovskite Photovoltaic Cell Using Cation-Doped Brookite TiO2 Top Buffer.

Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO2 brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO2 NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO2 NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties.

Monodispersed FeS nanoparticles confined in 3D interconnected carbon nanosheets network as an anode for high-performance lithium-ion batteries

Transition metal sulfides as the most prominent candidates with high theoretical capacities; however, serious agglomeration and enormous volumetric variation limit its application in lithium-ion batteries. Herein, a chemical blowing strategy for the synthesis of FeS nanoparticles encapsulated into 3D porous carbon framework via chemical vapor deposition method and subsequent sulfidation process. In the constructed architecture, the monodispersed FeS nanoparticles are fully encapsulated in graphitic carbon, simultaneously, confined in 3D architecture composed of 2D graphitic carbon nanosheets. The unique architecture provides a facilitated transport pathway, enhances electron conductivity and buffers the volumetric expansion of FeS. Consequently, the composite delivers a high reversible capacity of 1084.2 mAh g−1 at 0.1 A g−1, excellent rate capability (723.5 mAh g−1 at 1 A g−1), and outstanding cycling stability (a specific capacity of 848.3 mAh g−1 without decay is achieved at 0.5 A g−1). Therefore, the present work suggests that the novel design of 3D FeS/C material provides a strategy for achieving high-performance anodes in lithium-ion batteries. Uniformly monodispersed FeS nanoparticles confined in 3D interconnected carbon network was synthesized by using chemical vapor deposition method and subsequent sulfidation process. The hybrid electrode exhibits excellent performance with a reversible capacity of 1084.2 mAh g−1 at 0.1 A g−1 as well as outstanding cycling stability performance of 848.3 mAh g−1 at 0.5 A g−1 after 170 cycles.

Electron buffer formation through coupling thiosulfate-dependent denitratation with anammox in a single-stage sequencing batch reactor

The combination of thiosulfate-dependent denitratation and anammox in a single-stage reactor provides a feasible way to improve total nitrogen removal. The molar ratios of NH4+/NO3− and S2O32−/NO3− were confirmed to be two key factors affecting the reactor performance. The optimal total nitrogen removal efficiency of 99.4% was achieved at NH4+/NO3− of 0.75 and S2O32−/NO3− of 0.85. The multiple thiosulfate oxidation pathways contribute to electron buffers generated in the system. A novel isotope labeling method using 15N was applied to reveal N transformation pathways and a 3-step model was proposed. The nitrate was first converted to nitrite or nitric oxide (NO) by sulfur-oxidizing bacteria. In the second step, both nitrite and NO were utilized by anammox bacteria. Finally, the nitrate generated from anammox could be removed using sulfur deposits as electron donors. The findings provide a potential solution for mainstream nitrogen removal.

Preparation and characterization of MoSe2/CH3NH3PbI3/PMMA perovskite solar cells using polyethylene glycol solution

This paper presents a novel solar cell with FTO/MoSe2/perovskite/PMMA/C60/AZO/silver nanostructures. The hole-transporting material (HTM), active absorber layer, electron-transporting material (ETM), electron buffer layer, and transparent-conducting oxide layer were made of MoSe2, MAPbI3, PMMA, fullerene, and Al-doped ZnO, respectively. The SEM analysis confirmed that the MAPbI3 perovskite crystal size increased with the annealing temperature of the MoSe2 HTM films. The unique modified PMMA ETM films have been prepared and characterized at various thicknesses. At the optimal thickness of 25 nm, the experimental results showed that the multilayer solar cell's open-circuit voltage increased from 0.99 V to 1.11 V, and the short-circuit current value was elevated from 16.98 mA/cm2 to 21.11 mA/cm2. The device fill factor value was also improved from 60.67% to 76.12%. Thus, the device power-conversion efficiency exhibited significant improvement from 10.2% to 18.0%. In addition, the output power Pmax was as good as 1.79 mW. The PMMA, in conjunction with fullerene C60, has become an excellent candidate for the role of charge transporting for the multilayer perovskite solar cells.

Fabrication of a ternary carbon dots/CoO/g‐C3N4 nanocomposite photocatalyst with enhanced visible‐light‐driven photocatalytic hydrogen production

AbstractBACKGROUNDPhotocatalytic hydrogen (H2) production using sunlight is a promising solution for obtaining clean renewable energy. Therefore, the study of efficient, nontoxic and stable photocatalysts is very important.RESULTSA novel ternary carbon dots/cobalt monoxide/graphitic carbon nitride (CDs/CoO/g‐C3N4) composite photocatalyst was prepared by a simple solvothermal method for photocatalytic H2 production under visible light irradiation (λ > 420 nm). Compared with single semiconductors CoO and g‐C3N4, and binary composite CoO/g‐C3N4, the ternary CDs/CoO/g‐C3N4 nanocomposite exhibited higher photocatalytic performance. The optimal photocatalytic H2 rate of CDs/CoO/g‐C3N4 photocatalyst was 987.4 μmol g−1·h−1 with the apparent quantum efficiency of 2.39% at 420 nm. This enhanced photocatalytic activity can be attributed to the synergy effect of strong absorption and electron buffer property of CDs as well as the merits of the internal heterojunction formed between CoO and g‐C3N4.CONCLUSIONSThis work provides a new approach to the design of a high‐efficiency composite photocatalyst for converting solar energy into chemical fuel. © 2020 Society of Chemical Industry

Multi-component hierarchical hollow Co–Mo–O nanocages anchored on reduced graphene oxide with strong interfacial interaction for lithium-ion batteries

Transition metal oxides (TMOs) with high capacity have been extensively studied as promising anode candidates for lithium-ion batteries (LIBs). However, the intrinsic low electrical conductivity, sluggish reaction kinetics and dramatic volume expansion greatly restrict their practical applications. In the present work, we delicate design and synthesis of an advanced composite consisting of multi-component CoO/MoO2/CoMoO4 hierarchical hollow nanocages anchored on reduced graphene oxide (named as Co–Mo–O NCs/rGO composite) with strong interfacial interaction. The hierarchical hollow structure is beneficial for large electrode/electrolyte contact area and fast ion diffusion. Meanwhile, graphene can provide rapid electron transport pathway and buffer the volume change. As a result, the Co–Mo–O NCs/rGO composite exhibits excellent lithium storage performance in aspects of high reversible specific capacity (964 mA h g−1 at 0.1 A g−1), good rate capability (333 mA h g−1 at 5 A g−1) and long-term cycling performance (731 mA h g−1 at 1 A g−1 after 400 cycles). Moreover, electrode kinetics analysis further reveals the capacitive-controlled lithium ion storage mechanism in the Co–Mo–O NCs/rGO composite. The present work would demonstrate the importance of integrating multi-component TMOs hierarchical hollow structures and graphene into one intriguing architecture to boost the electrochemical performance.

Performance Evaluation of a Hybrid Buffer-Based Optical Packet Switch Router

Abstract Recently, in the present day’s data center systems an explosive growth has been observed in data traffic, which restricts the speed of exiting data communication network. To solve such problem, fiber optical-based optical communication system is preferred choice. In this paper, an arrayed waveguide grating (AWG)-based optical packet switch is presented in which priority among packets is implemented effectively. This switch is a recirculating loop buffer-based switch in which a hybrid buffering (optical + electrical) technique is used for storing packets into the buffer. The power budget analysis of switch is presented in various conditions, when packet passes through the optical or electronic buffers. Comparison of optical and electronic buffering is done in terms of power required for the correct operation of the switch. In this paper, a comparison is performed between our proposed switch with recently published switch designs. The result presented in this paper clearly reveals that the performance of our proposed switch is far better than other previously published switch architecture. The major beauty of our proposed switch is that in this design priority among packets implemented effectively.

Synergy of Electron Transfer and Electron Utilization via Metal–Organic Frameworks as an Electron Buffer Tank for Nicotinamide Regeneration

Solar energy conversion by photocatalysis holds promise in energy supply, but its efficiency is hindered by the mismatch in charge generation, transfer, and utilization. In natural photosynthesis, ...

Inverted polymer LEDs with solution-processed nano-hybrid electron buffer layers

We fabricated multilayered inverted polymer-based LEDs (iPLEDs) consisting of several types of solution-processed electron injection layer (EIL)/F8BT [green light emitting polymer (LEP)] or polyfluorene-based blue LEP (PFO)/TFB (hole-transporting layer)/MoO3/Ag structures. We compared the electrical properties of hybrid iPLEDs with solution-processed hybrid EILs deposited at low temperature (<120 °C) consisting of ZnO/polyethyleneimine (PEI), PEI/tantalum oxide nanosheet (TaO-NS), and PEI/TaO-NS/TmPyPB multilayers. The combination of PEI dipole and ultra-thin TaO-NS (∼1 nm) layers improved the EL efficiency and operating voltages owing to the energy level shift of ∼1 eV and the effective hole blocking at the ITO/TaO-NS/LEP interface. However, a considerable barrier height of >0.5 eV still existed at the TaO-NS/PFO interface. The insertion of electron-transporting small molecules between the TaO-NS and PFO layer effectively reduced the electron injection barrier height and electron transport properties of the multilayered iPLEDs resulting in improved EQE and operating voltage for the blue-light iPLEDs.

Construction of Sn-P-graphene microstructure with Sn-C and P-C co-bonding as anodes for lithium-ion batteries.

In this work, a P-Sn@G composite is synthesized using a direct high-energy ball milling (HEBM) method with P, Sn, and expanded graphite (EG). The in situ formed few layered graphene (FLG) prevents the formation of Sn4P3 and establishes strong Sn-C and P-C co-bonding in the resultant P-Sn@G composite. Excellent lithium storage is also revealed due to the key effect of FLG to benefit the electronic transfer and buffer expansion stress of the electrode from Sn and P.

High voltage vacuum-processed perovskite solar cells with organic semiconducting interlayers.

In perovskite solar cells, the choice of appropriate transport layers and electrodes is of great importance to guarantee efficient charge transport and collection, minimizing recombination losses. The possibility to sequentially process multiple layers by vacuum methods offers a tool to explore the effects of different materials and their combinations on the performance of optoelectronic devices. In this work, the effect of introducing interlayers and altering the electrode work function has been evaluated in fully vacuum-deposited perovskite solar cells. We compared the performance of solar cells employing common electron buffer layers such as bathocuproine (BCP), with other injection materials used in organic light-emitting diodes, such as lithium quinolate (Liq), as well as their combination. Additionally, high voltage solar cells were obtained using low work function metal electrodes, although with compromised stability. Solar cells with enhanced photovoltage and stability under continuous operation were obtained using BCP and BCP/Liq interlayers, resulting in an efficiency of approximately 19%, which is remarkable for simple methylammonium lead iodide absorbers.

Flower-like NiO/ZnO hybrid coated with N-doped carbon layer derived from metal-organic hybrid frameworks as novel anode material for high performance sodium-ion batteries

Metal-organic hybrid frameworks are considered as the promising precursor to prepare high performance anode materials for sodium-ion batteries (SIBs). In the present work, flower-like NiO/ZnO@NC with hollow and porous structure was prepared via a facile solvothermal and calcination process. The hollow and porous structure not only improve the electron transport capability, and but also inhibits the aggregation and accommodates the volume change of NiO/ZnO@NC. Meanwhile, the coated amorphous carbon layer could also increase the electron conductivity and buffer the huge volume expansion of active material NiO/ZnO. When used as anode for SIBs, NiO/ZnO@NC demonstrates a high specific capacity of 300 mAh g−1 with good cycling stability for 150 cycles, fast charge and discharge capability (154 mAh g−1 at 2500 mA g−1) and superior long cycling life at high current density for 2500 cycles. The strategy in this work should provide a new insight into fabrication novel structural anode materials for high performance SIBs.

Porosity‐ and Graphitization‐Controlled Fabrication of Nanoporous Silicon@Carbon for Lithium Storage and Its Conjugation with MXene for Lithium‐Metal Anode

AbstractSilicon (Si) and lithium metal are the most favorable anodes for high‐energy‐density lithium‐based batteries. However, large volume expansion and low electrical conductivity restrict commercialization of Si anodes, while dendrite formation prohibits the applications of lithium‐metal anodes. Here, uniform nanoporous Si@carbon (NPSi@C) from commercial alloy and CO2 is fabricated and tested as a stable anode for lithium‐ion batteries (LIBs). The porosity of Si as well as graphitization degree and thickness of the carbon layer can be controlled by adjusting reaction conditions. The rationally designed porosity and carbon layer of NPSi@C can improve electronic conductivity and buffer volume change of Si without destroying the carbon layer or disrupting the solid electrolyte interface layer. The optimized NPSi@C anode shows a stable cyclability with 0.00685% capacity decay per cycle at 5 A g−1 over 2000 cycles for LIBs. The energy storage mechanism is explored by quantitative kinetics analysis and proven to be a capacitance‐battery dual model. Moreover, a novel 2D/3D structure is designed by combining MXene and NPSi@C. As lithiophilic nucleation seeds, NPSi@C can induce uniform Li deposition with buffered volume expansion, which is proven by exploring Li‐metal deposition morphology on Cu foil and MXene@NPSi@C. The practical potential application of NPSi@C and MXene@NPSi@C is evaluated by full cell tests with a Li(Ni0.8Co0.1Mn0.1)O2 cathode.