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In recent years, the development of highly active and selective electrocatalysts for the electrochemical reduction of CO2 to produce CO and formic acid has aroused great interest, and can reduce environmental pollution and greenhouse gas emissions. Due to the high utilization of atoms, atom-dispersed catalysts are widely used in CO2 reduction reactions (CO2RRs). Compared with single-atom catalysts (SACs), multi-atom catalysts have more flexible active sites, unique electronic structures and synergistic interatomic interactions, which have great potential in improving the catalytic performance. In this study, we established a single-layer nitrogen-graphene-supported transition metal catalyst (TM-C2N1) based on density functional theory, facilitating the reduction of CO2 to CO or HCOOH with single-atom and multi-atomic catalysts. For the first time, the TM-C2N1 monolayer was systematically screened for its catalytic activity with ab initio molecular dynamics, density of states, and charge density, confirming the stability of the TM-C2N1 catalyst structure. Furthermore, the Gibbs free energy and electronic structure analysis of 3TM-C2N1 revealed excellent catalytic performance for CO and HCOOH in the CO2RR with a lower limiting potential. Importantly, this work highlights the moderate adsorption energy of the intermediate on 3TM-C2N1. It is particularly noteworthy that 3Mo-C2N1 exhibited the best catalytic performance for CO, with a limiting potential (UL) of -0.62 V, while 3Ti-C2N1 showed the best performance for HCOOH, with a corresponding UL of -0.18 V. Additionally, 3TM-C2N1 significantly inhibited competitive hydrogen evolution reactions. We emphasize the crucial role of the d-band center in determining products, as well as the activity and selectivity of triple-atom catalysts in the CO2RR. This theoretical research not only advances our understanding of multi-atomic catalysts, but also offers new avenues for promoting sustainable CO2 conversion.
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Solid-state lithium metal batteries (LMBs) are still plagued with low ionic conductivity and inferior interfacial contact, which hinder their practical implementation. Herein, a quasi-solid-state composite electrolyte, poly(1,3-dioxolane) (PDOL)/glassy ZIF-62 (PGZ) with fast ion transport and intimate interface contact, is fabricated via in situ polymerization. The in situ polymerization of DOL in an electrolyte matrix not only improves the exterior interface between electrolyte/electrode but also optimizes the inner interfaces among glassy particles, rendering PGZ as an uninterrupted ionic conductor. Moreover, PGZ inherits the superior ionic conductivity and the robust dendrite prohibition of glassy MOFs originating from their grain-boundary-free nature, isotropy, and abundant groups containing N species. As expected, our proposed PGZ exhibits a prominent ionic conductivity of 6.3 × 10-4 S cm-1 at 20 °C. Li|PGZ|LiFePO4 delivers an outstanding rate performance (103 mAh g-1 at 4C) and a stable cycling capacity (118 mAh g-1 at 1C over 1000 cycles). PGZ also presents excellent low-temperature cycling performance with 75 mAh g-1 for 480 cycles at -20 °C and excellent flame retardance. Even at a high loading of 12.1 mg cm-2, it can still discharge at 140 mAh g-1 for 100 cycles. Hence, PGZ prepared via in situ polymerization holds enormous prospects as a solid-state electrolyte for high-performance and safe LMBs.
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Owing to highly theoretical capacity of 3579 mAh/g for lithium-ion storage at ambient temperature, silicon (Si) becomes a promising anode material of high-performance lithium-ion batteries (LIBs). However, the large volume change (â¼300 %) during lithiation/delithiation and low conductivity of Si are challenging the commercial developments of LIBs with Si anode. Herein, a sandwich structure anode that Si nanoparticles sandwiched between carbon nanotube (CNT) and silicon carbide (SiC) has been successfully constructed by acetylene chemical vapor deposition and magnesiothermic reduction reaction technology. The SiC acts as a stiff layer to inhibit the volumetric stress from Si and the inner graphited CNT plays as the matrix to cushion the volumetric stress and as the conductor to transfer electrons. Moreover, the combination of SiC and CNT can relax the surface stress of carbonaceous interface to synergistically prevent the integrated structure from the degradation to avoid the solid electrolyte interface (SEI) reorganization. In addition, the SiC (111) surface has a strong ability to adsorb fluoroethylene carbonate molecule to further stabilize the SEI. Consequently, the CNT/SiNPs/SiC anode can stably supply the capacity of 1127.2 mAh/g at 0.5 A/g with a 95.6 % capacity retention rate after 200 cycles and an excellent rate capability of 745.5 mAh/g at 4.0 A/g and 85.5 % capacity retention rate after 1000 cycles. The present study could give a guide to develop the functional Si anode through designing a multi-interface with heterostructures.
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Although silicon has a high volumetric energy density as an anode material for Li-ion batteries, its volumetric expansion and sluggish Li+ migration kinetics need to be urgently addressed. In this work, cage-like structure materials (HRPOSS) derived from the in situ hydrogen reduction of polyhedral oligomeric silsesquioxane (T8-type POSS) were constructed as an Si@C anode for Li-ion batteries. Benefiting from the intriguing features of the Si/N double gradient and even-distributed silicon, HRPOSS-6 exhibited faint volume changes and fast ion-electron kinetics. Moreover, the uniformly immobilized nano-silicic and concentration gradient were favorable for accelerated ion migration. Therefore, HRPOSS-6 exhibited good electrochemical performances given that its cage structure could relieve the volume expansion. HRPOSS-6 demonstrated a high reversible capacity of 1814.1 mA h g-1 and long cycling performance after 200 cycles with 635 mA h g-1 at a current density of 0.5 A g-1. Accordingly, this Si/C/N composite exhibited great potential for high energy Li-ion batteries, where the corresponding full-cell (HRPOSS-6//LiNi0.6Co0.2Mn0.2O2) showed a cycle life of 200 cycles with over 80% capacity retention at rate of 1C. This work exploits the concentration gradients of dual elements for the capacity improvement of Si anodes and offers insight into the development of high-performance Si@C anode materials for advanced Li-ion batteries.
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Lithium (Li) metal is a highly desirable anode for all-solid-state lithium-ion batteries (ASSLBs) due to its high theoretical capacity and being well matched with solid-state electrolytes. However, the practical applications of Li metal anode are hindered by the uneven Li metal plating/stripping behavior and poor contact between electrolyte and Li anode. Herein, a convenient and efficient strategy to construct the Li3 N-based interlayer between solid poly(ethylene oxide) (PEO) electrolyte and Li anode is proposed by inâ situ thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN) additive. The evolved Li3 N nanoparticles are capable of combining LiF, cyano derivatives and PEO electrolyte to form a buffer layer of about 0.9â µm during the cell cycle, which can buffer Li+ concentration and homogenize Li deposition. The Li||Li symmetric cells with Li3 N-based interlayer show excellent cycle stability at 0.2â mA cm-2 , which is at least 4â times longer cycle life than that of PEO electrolytes without Li3 N layer. This work provides a convenient strategy for designing interface engineering between solid-state polymer electrolyte and Li anode.
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Suministros de Energía Eléctrica , Litio , Electrodos , Galvanoplastia , IngenieríaRESUMEN
Poor selectivity is a common problem faced by gas sensors. In particular, the contribution of each gas cannot be reasonably distributed when a binary mixture gas is co-adsorbed. In this paper, taking CO2 and N2 as an example, density functional theory is used to reveal the mechanism of selective adsorption of a transition metal (Fe, Co, Ni, and Cu)-decorated InN monolayer. The results show that Ni decoration can improve the conductivity of the InN monolayer while at the same time demonstrating an unexpected affinity for binding N2 instead of CO2. Compared with the pristine InN monolayer, the adsorption energies of N2 and CO2 on the Ni-decorated InN are dramatically increased from -0.1 to -1.93 eV and from -0.2 to -0.66 eV, respectively. Interestingly, for the first time, the density of states demonstrates that the Ni-decorated InN monolayer achieves a single electrical response to N2, eliminating the interference of CO2. Furthermore, the d-band center theory explains the advantage of Ni decorated in gas adsorption over Fe, Co, and Cu atoms. We also highlight the necessity of thermodynamic calculations in evaluating practical applications. Our theoretical results provide new insights and opportunities for exploring N2-sensitive materials with high selectivity.
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Lithium-sulfur batteries have great potential for next-generation electrochemical storage systems owing to their high theoretical specific energy and cost-effectiveness. However, the shuttle effect of soluble polysulfides and sluggish multi-electron sulfur redox reactions has severely impeded the implementation of lithium-sulfur batteries. Herein, we prepared a new type of Ti3C2-TiO2 heterostructure sandwich nanosheet confined within polydopamine derived N-doped porous carbon. The highly polar heterostructures sandwich nanosheet with a high specific surface area can strongly absorb polysulfides, restraining their outward diffusion into the electrolyte. Abundant boundary defects constructed by new types of heterostructures reduce the overpotential of nucleation and improve the nucleation/conversion redox kinetics of Li2S. The Ti3C2-TiO2@NC/S cathode exhibited discharge capacities of 1363, and 801 mAh g-1 at the first and 100th cycles at 0.5C, respectively, and retained an ultralow capacity fade rate of 0.076% per cycle over 500cycles at 1.0C. This study provides a potential avenue for constructing heterostructure materials for electrochemical energy storage and catalysis.
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Lithium-sulfur battery suffers from sluggish kinetics at low temperatures, resulting in serious polarization and reduced capacity. Here, this work introduces medium-entropy-alloy FeCoNi as catalysts and carbon nanofibers (CNFs) as hosts. FeCoNi nanoparticles are in suit synthesized in cotton-derived CNFs. FeCoNi with atomic-level mixing of each element can effectively modulate lithium polysulfides (LiPSs), multiple components making them promising to catalyze more LiPSs species. The higher configurational entropy endows FeCoNi@CNFs with extraordinary electrochemical activity, corrosion resistance, and mechanical properties. The fractal structure of CNFs provides a large specific surface area, leaving room for volume expansion and Li2 S accumulation, facilitating electrolyte wetting. The unique 3D conductive network structure can suppress the shuttle effect by physicochemical adsorption of LiPSs. This work systematically evaluates the performance of the obtained Li2 S6 /FeCoNi@CNFs electrode. The initial discharge capacity of Li2 S6 /FeCoNi@CNFs reaches 1670.8 mAh g-1 at 0.1 C under -20 °C. After 100 cycles at 0.2 C, the capacity decreases from 1462.3 to 1250.1 mAh g-1 . Notably, even under -40 °C at 0.1 C, the initial discharge capacity of Li2 S6 /FeCoNi@CNFs still reaches 1202.8 mAh g-1 . After 100 cycles at 0.2 C, the capacity retention rate is 50%. This work has important implications for the development of low-temperature Li-S batteries.
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Porous carbon has been one desirable electrode material for supercapacitors, but it is still a challenge to balance the appropriate mesopore volume and a high specific surface area (SSA). Herein, a good balance between a high SSA and mesopore volume in biomass-derived porous carbon is realized by precarbonization of wheat husk under air atmosphere via a chloride salt sealing technique and successive KOH activation. Due to the role of molten salt generating mesopores in the precarbonized product, which can further serve as the active sites for the KOH activation to form micropores in the final carbon material, the mesopore-micropore structure of the porous carbon can be tuned by changing the precarbonization temperature. The appropriate amount of mesopores can provide more expressways for ion transfer to accelerate the transport kinetics of diffusion-controlled processes in the micropores. A high SSA can supply abundant sites for charge storage. Therefore, the porous carbon with a good balance between the SSA and mesopores exhibits a specific gravimetric capacitance of 402 F g-1 at 1.0 A g-1 in a three-electrode system. In a two-electrode symmetrical supercapacitor, the biomass-derived porous carbon also delivers a high specific gravimetric capacitance of 346 F g-1 at 1.0 A g-1 and a good cycling stability, retaining 98.59% of the initial capacitance after 30,000 cycles at 5.0 A-1. This work has fundamental merits for enhancing the electrochemical performance of the biomass-derived porous carbon by optimizing the SSA and pore structures.
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As an intelligent response system, self-healing anticorrosion materials containing nanocontainers have aroused increasing demands. It is highly expected that the nanocontainers can rapidly respond on corrosion signals to efficiently release corrosion inhibitors, meanwhile to avoid an undesirable leakage before the local corrosion happening. Herein, zinc oxide quantum dot (ZnO-QD)-sealed hollow mesoporous TiO2 nanocontainers loading with 14.2% benzotriazole (BTA) inhibitor have been successfully prepared [hollow mesoporous titanium dioxide nanospheres (HMTNs)-BTA@ZnO-QDs]. ZnO-QDs play the multifunctional roles on anticorrosion of the self-healing coating. The corrosion tests of coatings on the carbon steel well demonstrate that ZnO-QDs can not only act as a valve to seal and release BTA on the time but also act as a precursor to produce the protective film of Zn(OH)2 by the reaction of Zn2+ ions with OH- around the cathode region to inhibit the corrosion of carbon steel. After being soaked in 3.5% NaCl solution for 30 days, the |Z|0.01 Hz value of the coating with HMTNs-BTA@ZnO-QDs still maintains at 2.87 × 107 Ω cm2. Once the defects are formed in the coating, the acid-responsive ZnO-QD valves are rapidly decomposed to release BTA inhibitor; meanwhile, the resulted Zn(OH)2 layer prevent the carbon steel substrate from corrosion in the cathode area. Therefore, it could be promising that the present design of the nanocontainers matching with the multifunctional ZnO-QDs can offer a valuable strategy to construct the self-healing and anticorrosion coatings with a multiresponse to the corrosion environment.
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A microfluidic manipulation system that can sense a liquid and control its flow is highly desirable. However, conventional sensors and motors have difficulty fitting the limited space in microfluidic devices; moreover, fast sensing and actuation are required because of the fast liquid flow in the hollow fibre. In this study, fast torsional and tensile actuators were developed using hollow fibres employing spiral nonlinear stress, which can sense the fluid temperature and sort the fluid into the desired vessels. The fluid-driven actuation exhibited a highly increased response speed (27 times as fast as that of air-driven actuation) and increased power density (90 times that of an air-driven solid fibre actuator). A 0.5 K fluid temperature fluctuation produced a 20° rotation of the hollow fibre. These high performances originated from increments in both heat transfer and the average bias angle, which was understood through theoretical analysis. This work provides a new design strategy for intelligent microfluidics and inspiration for soft robots and smart devices for biological, optical, or magnetic applications.
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Microfluídica , Robótica , Dispositivos Laboratorio en un Chip , TemperaturaRESUMEN
Spider silk is a natural polymeric fiber with high tensile strength, toughness, and has distinct thermal, optical, and biocompatible properties. The mechanical properties of spider silk are ascribed to its hierarchical structure, including primary and secondary structures of the spidroins (spider silk proteins), the nanofibril, the "core-shell", and the "nano-fishnet" structures. In addition, spider silk also exhibits remarkable properties regarding humidity/water response, water collection, light transmission, thermal conductance, and shape-memory effect. This motivates researchers to prepare artificial functional fibers mimicking spider silk. In this review, the authors summarize the study of the structure and properties of natural spider silk, and the biomimetic preparation of artificial fibers from different types of molecules and polymers by taking some examples of artificial fibers exhibiting these interesting properties. In conclusion, biomimetic studies have yielded several noteworthy findings in artificial fibers with different functions, and this review aims to provide indications for biomimetic studies of functional fibers that approach and exceed the properties of natural spider silk.
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Fibroínas , Seda , Biomimética , Fibroínas/química , Estructura Secundaria de Proteína , Seda/química , Resistencia a la TracciónRESUMEN
Large-scale implementation of all-solid-state lithium batteries is impeded by the physical limitations of the interface between the electrode and solid electrolyte; specifically, high resistance and poor stability, as well as poor compatibility with Li+ migration. We report double ionic-electronic transfer interface layers grown at electrode-electrolyte interfaces by inâ situ polymerization of 2,2'-bithiophene in polyethylene oxide (PEO) electrolyte. For all-solid-state LiFePO4 â¥PT-PEO-PTâ¥Li cells, the formation of a conductive polythiophene (PT) layer at the cathode-electrolyte interface resulted in an at least sevenfold decrease in interface resistance, and realized a capacity retention of about 94 % after 1000â cycles along with a lower polarization voltage under a rate of 2â C. The mixed ionic-electronic conductive layers imparted superior interface stability and contact while keeping good compatibility with the Li anode.
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The development of low-cost, highly efficient and stable non-precious metal electrocatalyst for the oxygen reduction reaction (ORR) substituting Pt has attracted much attention. Herein, we developed a promising structural platform for the fabrication of carbon nanospheres functionalized with hollow nanostructures of M-NHCS (M = Fe, Co and Mn) based on metallo-deuteroporphyrins (MDP). Benefited from the multi-layered active sites and hollow substrate with more exposed active surface area, convenient channels for the transport of electrons, the resulting Fe-NHCS electrocatalysts exhibit enhanced electrocatalytic performance in ORR with an onset potential of 0.90 V (versus RHE), and a high selectivity in the direct 4-electron pathway. The Fe-NHCS electrocatalysts also show a good methanol tolerance superior to Pt/C catalysts and an extremely high stability with only 13.0 mV negative after 5000 cycles in alkaline media. Experiments have verified that maintaining the multi-layered Fe-N-C active sites and hollow substrate were essential to deliver the high performance for ORR. The work opens new avenues for utilizing MDP-based materials in future energy conversion applications.
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Lithium (Li) is the lightest and most electronegative metallic element and has been considered the ultimate anode choice for energy storage systems with high energy density. However, uncontrollable dendrite formation caused by high ion transfer resistance and low Li atom diffusion, and dendrite growth with large volume expansion and high electronegative activity, result in severe safety concerns and poor coulombic efficiency. In this review, the latest progress is presented from the viewpoint of dendrite evolution (from dendrite formation to growth) as the main line to understand the factors that influence the deposition chemistry. For the dendrite formation, specific attention is focused on the four distinct but interdependent factors: (a) how the dielectric constant, donor number, viscosity and salt concentration affect the movement of solvated Li+ in nonaqueous electrolyte. (b) The effect of non-polar solvents and anions with polar groups or high concentration on the Li+ desolvation step. (c) The effect of the formation of solid electrolyte interphase (SEI), along with its specific adsorption and solvated structure, and its physical structure, chemical composition and growth thickness on Li+ diffusion. (d) The effect of the diffusion coefficient of the host material on Li atom migration. After dendrite formation, the attention is focused on two detrimental factors together with dendrite growth: (e) low coulombic efficiency; (f) large volume expansion. Correspondingly, the emphasis is placed on reducing the side reactions and minimizing the volume expansion. Conclusions and perspectives on the current limitations and future research directions are recommended. It is anticipated that the dynamic dendrite evolution can provide fresh insight into similar electrochemical reaction processes of other anode chemistries in nonaqueous electrolytes, ranging from a conversion-reaction metal anode (Li, Na, Al) and an alloying anode (LiAlx, NaAlx) to an intercalation-based anode (graphite, TiS2), as well as aqueous, ionic liquid and flow redox battery systems.
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Higher-efficiency, lower-cost refrigeration is needed for both large- and small-scale cooling. Refrigerators using entropy changes during cycles of stretching or hydrostatic compression of a solid are possible alternatives to the vapor-compression fridges found in homes. We show that high cooling results from twist changes for twisted, coiled, or supercoiled fibers, including those of natural rubber, nickel titanium, and polyethylene fishing line. Using opposite chiralities of twist and coiling produces supercoiled natural rubber fibers and coiled fishing line fibers that cool when stretched. A demonstrated twist-based device for cooling flowing water provides high cooling energy and device efficiency. Mechanical calculations describe the axial and spring-index dependencies of twist-enhanced cooling and its origin in a phase transformation for polyethylene fibers.
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Rechargeable batteries are considered promising replacements for environmentally hazardous fossil fuel-based energy technologies. High-energy lithium-metal batteries have received tremendous attention for use in portable electronic devices and electric vehicles. However, the low Coulombic efficiency, short life cycle, huge volume expansion, uncontrolled dendrite growth, and endless interfacial reactions of the metallic lithium anode are major obstacles in their commercialization. Extensive research efforts have been devoted to address these issues and significant progress has been made by tuning electrolyte chemistry, designing electrode frameworks, discovering nanotechnology-based solutions, etc. This Review aims to provide a conceptual understanding of the current issues involved in using a lithium metal anode and to unveil its electrochemistry. The most recent advancements in lithium metal battery technology are outlined and suggestions for future research to develop a safe and stable lithium anode are presented.
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The precise design of Si-based materials at the nanometer scale is a quite complex issue but of utmost importance for their present and potential applications. This paper reports the first attempt to address the electrochemical reduction of SiO2 at the nanometer scale. SiO2 nanoparticles are first covered with a uniform carbon layer with controlled thickness at an accuracy of a few nanometers, by pressure-pulsed chemical vapor deposition. With appropriate thickness, the carbon layer plays significant roles as a current path and also as a physical barrier against Si-crystal growth, and the SiO2 nanoparticles are successfully converted into extremely small Si nanocrystals (<20 nm) inside the shell-like carbon layer whose morphology is derived from the original SiO2 nanoparticles. Thus, the proposed electroreduction method offers a new synthesis strategy of Si-C nanocomposites utilizing the morphology of SiO2 nanomaterials, which are well known for a wide variety of defined and regular nanostructures. Owing to the volume difference of SiO2 and the corresponding Si, nanopores are generated around the Si nanocrystals. It has been demonstrated that the nanopores around the Si nanocrystals are effective to improve cycle performance of Si as a negative electrode for lithium-ion batteries. The present method is in principle applicable to various SiO2 nanomaterials, and thus, offers production of a variety of Si-C composites whose carbon nanostructures can be defined by their parent SiO2 nanomaterials.
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Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4-PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.
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Bencenosulfonatos/química , Electrólisis/métodos , Agua/química , Benzoquinonas/química , Hidroquinonas/químicaRESUMEN
Coconut shell-based activated carbon (AC) were prepared by CO2 activation, and then the ACs with higher mesopore ratio were obtained by steam activation and by impregnating iron catalyst followed by steam activation, respectively. The AC with the highest mesopore ratio (AChmr) shows superior capacitive behavior, power output and high-frequency performance in supercapacitors. The results should attribute to the connection of its wide micropores and mesopores larger than 3 nm, which is more favorable for fast ionic transportation. The pore size distribution exhibits that the mesopore ratios of the ACs are significantly increased by reactivation of steam or catalyst up to 75% and 78%, respectively. As evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic measurements, the AChmr shows superior capacitive behaviors, conductivity and performance of electrolytic ionic transportation. The response current densities are evidently enhanced through the cyclic voltammery test at 50 mV/sec scan rate. The electrochemical impedance spectroscopy demonstrates that the conductivity and ion transport performance of the ACs are improved. The specific capacitances of the ACs were increased from 140 to 240 F/g at 500 mA/g current density. The AChmr can provide much higher power density while still maintaining good energy density, and demonstrate excellent high-frequency performances. The pore structure and conductivity of the AChmr also improve the cycleability and self-discharge of supercapacitors. Such AChmr exhibits a great potential in supercapacitors, particularly for applications where high power output and good high-frequency capacitive performances are required.