First-principles density functional theory calculations are first used to study possible reaction mechanisms of molybdenum carbide (Mo2C) as cathode catalysts in Li-CO2 batteries. By systematically ...investigating the Gibbs free energy changes of different intermediates during lithium oxalate (Li2C2O4) and lithium carbonate (Li2CO3) nucleations, it is theoretically demonstrated that Li2C2O4 could be stabilized as the final discharge product, preventing the further formation of Li2CO3. The surface charge distributions of Li2C2O4 adsorbing onto catalytic surfaces are studied by using Bader charge analysis, given that electron transfers are found between Li2C2O4 and Mo2C surfaces. The catalytic activities of catalysts are intensively evaluated toward the discharge and charge processes by calculating the electrochemical free energy diagrams to identify the overpotentials. Our studies promote the understanding of electrochemical processes and shed more light on the design and optimization of cathode catalysts for Li-CO2 batteries.
The Li–CO2 battery is a promising energy storage device for wearable electronics due to its long discharge plateau, high energy density, and environmental friendliness. However, its utilization is ...largely hindered by poor cyclability and mechanical rigidity due to the lack of a flexible and durable catalyst electrode. Herein, flexible fiber‐shaped Li–CO2 batteries with ultralong cycle‐life, high rate capability, and large specific capacity are fabricated, employing bamboo‐like N‐doped carbon nanotube fiber (B‐NCNT) as flexible, durable metal‐free catalysts for both CO2 reduction and evolution reactions. Benefiting from high N‐doping with abundant pyridinic groups, rich defects, and active sites of the periodic bamboo‐like nodes, the fabricated Li–CO2 battery shows outstanding electrochemical performance with high full‐discharge capacity of 23 328 mAh g−1, high rate capability with a low potential gap up to 1.96 V at a current density of 1000 mA g−1, stability over 360 cycles, and good flexibility. Meanwhile, the bifunctional B‐NCNT is used as the counter electrode for a fiber‐shaped dye‐sensitized solar cell to fabricate a self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6%. Along with a stable voltage output, this design demonstrates great adaptability and application potentiality in wearable electronics with a breath monitor as an example.
A self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6% is fabricated using bifunctional bamboo‐like N‐doped carbon nanotube fiber as the cathode for the Li–CO2 battery and as the counter electrode for the dye‐sensitized solar cells simultaneously. The fiber‐shaped Li–CO2 batteries show high specific capacity, long cycle life, and high flexibility.
We report a one-pot hydrothermal approach to synthesize carbon coated-SnO2/graphene-sheet (SnO2-C/GNS) nanocomposite. Strong oxidation–reduction reactions to produce GNS by the traditional Hummers' ...method are avoided. The experiments show that the glucose and tin tetrachloride can intercalate into the thin graphite flake to exfoliate graphite and form SnO2-C/GNS nanocomposite simultaneously during the hydrothermal process. The approach is quite simple and green. Meanwhile, the prepared SnO2-C/GNS nanocomposite as an anode material of lithium-ion batteries exhibits higher lithium storage capacity and better cycling performance compared to SnO2 nanoparticle and SnO2-C microsphere. It still delivers the reversible capacity of 703 mA h g−1 after 80 cycles at a current density of 100 mA g−1 and maintains 443 mA h g−1 after 100 cycles at a current density of 1000 mA g−1. The improvement in the performance of SnO2-C/GNS nanocomposite can be attributed to the fully confinement of SnO2 nanoparticles between the GNS and the carbon layer, which can effectively prevent the detachment and agglomeration of SnO2 and preserve the integrity of the nanostructure during charge/discharge cycling.
► SnO2-C/GNS nanocomposite was synthesized by a one-pot hydrothermal approach. ► Strong oxidation and reduction process to produce GNS by Hummer's method is avoided. ► It exhibits excellent high-rate capability and cycling stability as anode material. ► The improved performance was attributed to the double carbon buffering matrix.
Amorphous red phosphorus/carbon nanotubes (ARPC) composites are prepared by planetary ball-milling technique with the pre-milling red phosphorus processes, consisting of uniformly distributing ...amorphous red phosphorus embedding in a three-dimensional conductive scaffold of interconnected carbon nanotubes (CNTs). Combining the three-dimensional conductive network with the amorphous red phosphorus can not only alleviate the volumetric change in the charging/discharging processes, but also provide conductive network for electron transport and dramatically improve the specific capacity, cycling stability and rate capability of the composite electrode. The ARPC composites deliver a high initial charge capacity of 2133.4 mAh g−1 at a current density of 0.05 C and maintain a reversible capacity of 998.5 mAh g−1 with a high Coulombic efficiency of approximately 99% after 50 cycles. Meanwhile, the composite can maintain high specific capacities of 1993.8 mAh g−1, 1896.9 mAh g−1, 1546.8 mAh g−1 and 816.6 mAh g−1 at 0.01 C, 0.05 C, 0.1 C and 0.5 C, respectively. Compared with that of the ball-milled amorphous red phosphorus with or without CNTs, the pre-milled ARPC composites show much better electrochemical performances.
•Amorphous red phosphorus/carbon nanotubes (ARPC) composites are produced by ball-milling.•Amorphous red phosphorus is embedded in a carbon nanotubes scaffold.•ARPC composites anode shows good cycling performance with high specific capacity.
Li–CO2 batteries are regarded as a promising candidate for the next‐generation high‐performance electrochemical energy storage system owing to their ultrahigh theoretical energy density and ...environmentally friendly CO2 fixation ability. Until now, the majority of reported catalysts for Li–CO2 batteries are in the powder state. Thus, the air electrodes are produced in 2D rigid bulk structure and their electrochemical properties are negatively influenced by binder. The nondeformable feature and unsatisfactory performance of the cathode have already become the main obstacles that hinder Li–CO2 batteries toward ubiquity for wearable electronics. In this work, for the first time, a flexible hybrid fiber is reported comprising highly surface‐wrinkled and N‐doped carbon nanotube (CNT) networks anchored on metal wire as the cathode integrated with high performance and high flexibility for fiber‐shaped Li–CO2 battery. It exhibits a large discharge capacity as high as 9292.3 mAh g−1, an improved cycling performance of 45 cycles, and a decent rate capability. A quasi‐solid‐state flexible fiber‐shaped Li–CO2 battery is constructed to illustrate the advantages on mechanical flexibility of this fiber‐shaped cathode. Experiments and theoretical simulations prove that those doped pyridinic nitrogen atoms play a critical role in facilitating the kinetics of CO2 reduction and evolution reaction, thereby enabling distinctly enhanced electrochemical performance.
A flexible hybrid fiber comprising highly surface‐wrinkled and N‐doped carbon nanotube (CNT) networks anchored on metal wire as the cathode integrated with high performance and high flexibility is reported for fiber‐shaped flexible Li–CO2 batteries. Abundant catalytic active sites originating from highly‐wrinkled surfaces and enhanced reaction kinetics by doped pyridinic nitrogen atoms improve the electrochemical performance of the battery.
Flexible fiber‐shaped sodium dual‐ion batteries (FSDIBS) as a proof of concept are fabricated by using the hierarchical ReS2 nanosheets anchored on the carbon nanotube (ReS2@CNT) fiber as anode and ...graphite on the CNT as cathode. Owing to large interlayer spacing and weak layer coupling force of the ReS2 nanosheets and the anion accommodation of the graphite combined with good flexibility of the CNT fiber, the FSDIBS demonstrate outstanding electrochemical performances with high working voltage and high specific volumetric energy density, durable cycling life, and good flexibility. The FSDIBS show a specific discharge capacity of 97.8 mAh cm−3 at a current density of 630 mA cm−3 and high specific energy density of 25.12 mWh cm−3 (based on the whole volume of the two electrodes) and superb stability with a capacity retention of 91.8% even after bending for 2100 cycles. Moreover, a series of ex situ/in situ characterizations are verified that the reversible shuttles of the Na+ cations and PF6‐ anions between the anode and cathode are simultaneously occurred during the charge/discharge process.
A novel fiber‐shaped sodium dual‐ion battery (FSDIB) is fabricated, which reveals excellent electrochemical properties, superb flexibility, and high energy density.
Sequence plays a critical role in enabling unique properties and functions of natural biomolecules, which has promoted the rapid advancement of synthetic sequence‐defined polymers in recent decades. ...Particularly, investigation of short chain sequence‐defined oligomers (also called discrete oligomers) on their properties has become a hot topic. However, most studies have focused on discrete oligomers with conjugated structures. In contrast, unconjugated oligomers remain relatively underexplored. In this study, three pairs of discrete oligomers with the same composition but different sequence for each pair are employed for investigating their glass transition temperatures (Tgs). The resultant Tgs of sequenced oligomers in each pair are found to be significantly different (up to 11.6 °C), attributable to variations in molecular packing as demonstrated by molecular dynamics and density function theory simulations. Intermolecular interaction is demonstrated to have less impact on Tgs than intramolecular interaction. The mechanistic investigation into two model dimers suggests that monomer sequence caused the difference in intramolecular rotational flexibility of the sequenced oligomers. In addition, despite having different monomer sequence and Tgs, the oligomers have very similar solubility parameters, which supports their potential use as effective oligomeric plasticizers to tune the Tgs of bulk polymer materials.
A remarkable impact of monomer sequence on glass transition temperatures of discrete unconjugated oligomers is reported. Evidenced by experimental analysis and computational simulations, changing monomer sequence results in altered degree of twisting of the oligomer backbone and distinct rotational flexibility of the sequenced oligomers, which thus caused the variation of glass transition temperatures.
Li–CO2 batteries are considered one of the promising power sources owing to ultrahigh energy density and carbon fixation. Nevertheless, the sluggish reaction kinetics of 4e− discharged process ...(Li2CO3) impede its potential application. One of the efficient strategies for developing cathode catalysts is to stabilize 2e− intermediate Li2C2O4 and improve reaction reversibility. However, long‐term catalysts of stabilized Li2C2O4 are barely achieved, whereas cycle stability is far from satisfactory level. Herein, non‐noble metal–based Mo3N2 is synthesized and employed as freestanding cathodes for Li–CO2 batteries. Owing to rich delocalized electrons of Mo2+ and reversible electron localization structure, freestanding Mo3N2 cathodes exhibit a low charge potential (3.28 V) with an ultralow potential gap (0.64 V), high energy efficiency of up to 80.46%, fast rate capability, and outstanding cycle stability (>910 h). In situ experiments and theoretical calculation verify that Mo3N2 stabilizes 2e− Li2C2O4 intermediate by the interaction of Mo2+ as active sites where Mo2+ promotes the transfer of outer electrons to O, prevents its disproportionation to Li2CO3, and promotes reaction kinetics, contributing to high energy efficiency and outstanding cycle reversibility. In addition, the pouch‐cells deliver ultrahigh energy density of up to 6350.7 W h kg−1 based on the mass of cathode materials.
Freestanding Mo3N2 nanotubes are directly applied as cathodes for 2e− discharge intermediate Li2C2O4‐based Li–CO2 batteries, which improve battery reaction reversibility and exhibit a high energy efficiency, high‐rate capability, outstanding cycle stability, and high energy density.
PSA is a type of proto-oncogene that is specifically and highly expressed in embryonic and prostate cancer cells, but not expressed in normal prostate tissue cells. The specific expression of ...prostate-specific antigen (PSA) is found to be related with the conditional transcriptional regulation of its promoter. Clustered regularly interspaced short palindromic repeats (CRISPR)-dCas9-KRAB is a newly developed transcriptional regulatory system that inhibits gene expression by interupting the DNA transcription process. Induction of CRISPR-dCas9-KRAB expression through the PSA promoter may help feedback inhibition of cellular PSA gene expression via single guide RNA (sgRNA), thereby monitoring and suppressing the malignant state of tumor cells. In this study, we examined the transcriptional activity of the PSA promoter in different prostate cancer cells and normal prostate epithelial cells and determined that it is indeed a prostate cancer cell-specific promoter.Then we constructed the CRISPR-dCas9-KRAB system driven by the PSA promoter, which can inhibit PSA gene expression in the prostate cancer cells at the transcriptional level, and therefore supress the malignant growth and migration of prostate cancer cells and promote their apoptosis in vitro. This study provides a potentially effective anti-cancer strategy for gene therapy of prostate cancer.
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