Combining high specific surface area (SSA) and superior electrical conductivity together at bulk state is very important for carbon materials in capacitive energy storage applications. Herein, by ...applying molten sodium metal to activate natural cotton at a relatively low processing temperature (800°C), we have obtained hierarchically porous graphitic carbon fibers (HPGCFs) with SSA up to 1716m2g−1 and a high degree of graphitization in the bulk state. This is advantageous compared to amorphous carbon fibers obtained by conventional thermal annealing and KOH-activation. The obtained HPGCFs show remarkable energy storage capability (61% capacitance retention from 1 to 60Ag−1). To further increase the capacitance value, anthraquinone (AQ) molecules have been selected to functionalize HPGCFs via π–π stacking interactions. Asymmetric supercapacitors have been assembled using HPGCFs as the positive electrode and AQ-HPGCFs as the negative electrode in aqueous H2SO4 solution. The device presents a large energy density (19.3Whkg−1 in the applied potential range between 0 and 1.2V) and ultrahigh power capability (up to 120Ag−1, a full charge–discharge within 0.8s).
Display omitted
•Natural cottons are activated using molten sodium at 800 °C.•Molten sodium activation is more effective than conventional KOH activation.•Asymmetric supercapacitors show outstanding performance.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The direct synthesis of hydrogen peroxide (H2O2) through the two‐electron oxygen reduction reaction is a promising alternative to the industrial anthraquinone oxidation process. Selectivity to H2O2 ...is however limited by the four‐electron pathway during oxygen reduction. Herein, it is reported that aminoanthraquinone confined isolated metal sites on carbon supports selectively steer oxygen reduction to H2O2 through the two‐electron pathway. Confining isolated NiNx sites under aminoanthraquinone increases the selectivity to H2O2 from below 55% to above 80% over a wide potential range. Spectroscopy characterization and density functional theory calculations indicate that isolated NiNx sites are confined within a nanochannel formed between the molecule and the carbon support. The confinement reduces the thermodynamic barrier for OOH* desorption versus further dissociation, thus increasing the selectivity to H2O2. It is revealed how tailoring noncovalent interactions beyond the binding site can empower electrocatalysts for the direct synthesis of H2O2 through oxygen reduction.
Aminoanthraquinone confined on isolated NiNx sites effectively modulates the electrocatalytic oxygen reduction reaction toward hydrogen peroxide (H2O2) production. The NiNx sites favor oxygen reduction to OOH*. Confinement effects created by the molecule on NiNx sites promote OOH* desorption to H2O2. The molecularly confined catalyst achieves the high selectivity above 80% for H2O2 with a small overpotential.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Rechargeable aqueous Zn–Mn batteries have garnered extensive attention for next‐generation high‐safety energy storage. However, the charge‐storage chemistry of Zn–Mn batteries remains controversial. ...Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2/Mn2+ dissolution−deposition reaction in strong acidic electrolytes. Herein, a Zn4SO4·(OH)6·xH2O (ZSH)‐assisted deposition−dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn–Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and ZnxMnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn–Mn batteries and guide the design of high‐capacity aqueous Zn batteries.
A new Zn4SO4·(OH)6·xH2O (ZSH)‐assisted deposition and dissolution reaction model is proposed and validated for aqueous Zn–Mn batteries in mild sulfate electrolytes. It is shown that MnO2 is not a compulsory cathode; and various metal oxides, including ZSH, ZnO, MgO, and CaO, can be used as the cathode materials for aqueous Zn batteries.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Hollow and hierarchical nanostructures have received wide attention in new‐generation, high‐performance, lithium ion battery (LIB) applications. Both TiO2 and Fe2O3 are under current investigation ...because of their high structural stability (TiO2) and high capacity (Fe2O3), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO2@Fe2O3 nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template‐assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g−1), improved cycle stability (530 mAh g−1 after 200 cycles at the current density of 200 mA g−1), as well as outstanding rate capability. This ALD‐assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices.
Hollow TiO2 nanorods with surface coated with Fe2O3 nanospikes are fabricated using atomic layer deposition and a sacrificial template. The LIB anode based on the obtained nanostructure exhibits a high reversible capacity (initial value 840 mAh g−1), improved cycle stability (530 mAh g−1 after 200 cycles at the current density of 200 mA g−1) as well as outstanding rate capability.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The progress of aqueous zinc batteries (AZBs) is limited by the poor cycling life due to Zn anode instability, including dendrite growth, surface corrosion, and passivation. Inspired by the ...anti‐corrosion strategy of steel industry, a compounding corrosion inhibitor (CCI) is employed as the electrolyte additive for Zn metal anode protection. It is shown that CCI can spontaneously generate a uniform and ≈30 nm thick solid‐electrolyte interphase (SEI) layer on Zn anode with a strong adhesion via ZnO bonding. This SEI layer efficiently prohibits water corrosion and guides homogeneous Zn deposition without obvious dendrite formation. This enables reversible Zn deposition and dissolution for over 1100 h under the condition of 1 mA cm−2 and 1 mAh cm−2 in symmetric cells. The Zn‐MnO2 full cells with CCI‐modified electrolyte deliver an ultralow capacity decay rate (0.013% per cycle) at 0.5 A g−1 over 1000 cycles. Such an innovative strategy paves a low‐cost way to achieve AZBs with long lifespan.
Inspired by the industrial steel pipeline protection, a compounding corrosion inhibitor (CCI) has been employed as the electrolyte additive for aqueous Zn metal anodes. The spontaneous deposition of CCI on Zn surface constructs a uniform organic layer which provides Zn2+ conduction and H2O repulsion. A strong adhesion between Zn and CCI leads to a dendrites‐free Zn electrodeposition and long cycling life of the aqueous Zn‐ion battery.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Hollow micro‐/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a “top‐down” casting process ...based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic‐layer‐deposition (ALD) Al2O3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)–carbon composite hollow fibers after removal of Al2O3. Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni‐based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for energy applications. Herein, the as‐obtained hollow V2O3–C fiber membrane is employed as a freestanding and flexible electrode for lithium‐ion capacitor. The device shows an impressive energy density and a high power density.
A thin and homogeneous atomic‐layer‐deposition Al2O3 layer is applied to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)–carbon composite hollow fibers after removal of Al2O3. The obtained freestanding hollow fibers may have a wider application than the metal‐ion capacitor that is demonstrated in this article.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
SnO2 nanowires directly grown on flexible substrates can be a good electrode for a lithium ion battery. However, Sn-based (metal Sn or SnO2) anode materials always suffer from poor stability due to a ...large volume expansion during cycling. In this work, we utilize atomic layer deposition (ALD) to surface engineer SnO2 nanowires, resulting in a new type of hollowed SnO2-in-TiO2 wire-in-tube nanostructure. This structure has radically improved rate capability and cycling stability compared to both bare SnO2 nanowires and solid SnO2@TiO2 core–shell nanowire electrodes. Typically a relatively stable capacity of 393.3 mAh/g has been achieved after 1000 charge–discharge cycles at a current density of 400 mA/g, and 241.2 mAh/g at 3200 mA/g. It is believed that the uniform hollow TiO2 shell provides stable surface protection and the appropriate-sized gap effectively accommodates the expansion of the interior SnO2 nanowire. This ALD-enabled method should be general to many other battery anode and cathode materials, providing a new and highly reproducible and controllable technique for improving battery performance.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis ...strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.
Various solution-based synthesis methods for common metal oxide nanostructures and associated reaction mechanisms are reviewed.
By employing in situ reduction of metal precursor and metal‐assisted carbon etching process, this study achieves a series of ultrafine transition metal‐based nanoparticles (Ni–Fe, Ni–Mo) embedded in ...N‐doped carbon, which are found efficient catalysts for electrolytic water splitting. The as‐prepared hybrid materials demonstrate outstanding catalytic activities as non‐noble metal electrodes rendered by the synergistic effect of bimetal elements and N‐dopants, the improved electrical conductivity, and hydrophilism. Ni/Mo2C@N‐doped porous carbon (NiMo‐polyvinylpyrrolidone (PVP)) and NiFe@N‐doped carbon (NiFe‐PVP) produce low overpotentials of 130 and 297 mV at a current density of 10 mA cm−2 as catalysts for hydrogen evolution reaction and oxygen evolution reaction, respectively. In addition, these binder‐free electrodes show long‐term stability. Overall water splitting is also demonstrated based on the couple of NiMo‐PVP||NiFe‐PVP catalyzer. This represents a simple and effective synthesis method toward a new type of nanometal–carbon hybrid electrodes.
A new way for metal–carbon composite: Ultrafine transition metal‐based nanoparticles (Ni‐Fe, Ni‐Mo) embedded in N‐doped carbon by employing in situ reduction of metal precursor and metal‐assisted carbon etching process. They are applied as efficient hydrogen evolution reaction and oxygen evolution reaction catalysts for water splitting.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The robotic surgical system has been applied in liver surgery. However, controversies concerns exist regarding a variety of factors including the safety, feasibility, efficacy, and cost-effectiveness ...of robotic surgery. To promote the development of robotic hepatectomy, this study aimed to evaluate the current status of robotic hepatectomy and provide sixty experts' consensus and recommendations to promote its development. Based on the World Health Organization Handbook for Guideline Development, a Consensus Steering Group and a Consensus Development Group were established to determine the topics, prepare evidence-based documents, and generate recommendations. The GRADE Grid method and Delphi vote were used to formulate the recommendations. A total of 22 topics were prepared analyzed and widely discussed during the 4 meetings. Based on the published articles and expert panel opinion, 7 recommendations were generated by the GRADE method using an evidence-based method, which focused on the safety, feasibility, indication, techniques and cost-effectiveness of hepatectomy. Given that the current evidences were low to very low as evaluated by the GRADE method, further randomized-controlled trials are needed in the future to validate these recommendations.
PDF
