Designing highly conducting metal-organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. ...Herein, a strategic design in which a metal-sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {Cu
(6-Hmna)(6-mn)·NH
}
(1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (-Cu-S-)
plane, is synthesized from the reaction of Cu(NO
)
, and 6,6'-dithiodinicotinic acid via the in situ cleavage of an S-S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm
) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.
Abstract
Nonnoble metal catalysts are low-cost alternatives to Pt for the oxygen reduction reactions (ORRs), which have been studied for various applications in electrocatalytic systems. Among them, ...transition metal complexes, characterized by a redox-active single-metal-atom with biomimetic ligands, such as pyrolyzed cobalt–nitrogen–carbon (Co–N
x
/C), have attracted considerable attention. Therefore, we reported the ORR mechanism of pyrolyzed Vitamin B12 using operando X-ray absorption spectroscopy coupled with electrochemical impedance spectroscopy, which enables operando monitoring of the oxygen binding site on the metal center. Our results revealed the preferential adsorption of oxygen at the Co
2+
center, with end-on coordination forming a Co
2+
-oxo species. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, corroborated with first-principle calculations, provide insight into metal active-site geometry and structural evolution during ORR, which could be used for developing material design strategies for high-performance electrocatalysts for fuel cell applications.
Flexible supercapacitors, a state‐of‐the‐art material, have emerged with the potential to enable major advances in for cutting‐edge electronic applications. Flexible supercapacitors are governed by ...the fundamentals standard for the conventional capacitors but provide high flexibility, high charge storage and low resistance of electro active materials to achieve high capacitance performance. Conducting polymers (CPs) are among the most potential pseudocapacitor materials for the foundation of flexible supercapacitors, motivating the existing energy storage devices toward the future advanced flexible electronic applications due to their high redox active‐specific capacitance and inherent elastic polymeric nature. This review focuses on different types of CPs‐based supercapacitor, the relevant fabrication methods and designing concepts. It describes recent developments and remaining challenges in this field, and its impact on the future direction of flexible supercapacitor materials and relevant device fabrications.
The conducting polymer‐based redox materials are bringing a revolution in the flexible pseudo‐capacitor applications. The future of the CPs‐based flexible energy storage devices hold even greater promise for a novel low cost, light‐weight and highly flexible devices.
Pharmaceutical drugs' removal from wastewater by photocatalytic oxidation process is considered as an attractive approach and environmentally friendly solution. This report aims to appraise the ...practical application potential of Ag/g-C3N4/ZnO nanorods toward the wastewater treatment of the pharmaceutical industry. The catalysts are synthesized by straightforward and environmentally-friendly strategies. Specifically, g-C3N4/ZnO nanorods heterostructure is constructed by a simple self-assembly method, and then Ag nanoparticles are decorated on g-C3N4/ZnO nanorods by a photoreduction route. The results show that three commercial drugs (paracetamol, amoxicillin, and cefalexin) with high concentration (40 mg L−1) are significantly degraded in the existence of a small dosage of Ag/g-C3N4/ZnO nanorods (0.08 g L−1). The Ag/g-C3N4/ZnO nanorods photocatalyst exhibits degradation performance of paracetamol higher 3.8, 1.8, 1.3 times than pristine g-C3N4, ZnO nanorods, and g-C3N4/ZnO nanorods. Furthermore, Ag/g-C3N4/ZnO nanorods have an excellent reusability and a chemical stability that achieved paracetamol degradation efficiency of 78% and remained chemical structure of the photocatalyst after five cycles. In addition, the photocatalytic mechanism explanation and comparison of photocatalytic drugs’ degradation ability have also been discussed in this study.
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•A small amount of Ag/gC3N4/ZnO degraded a high concentration of pollutants.•Valence band edge of Ag/gC3N4/ZnO is determined by XPS analysis.•Electrons play a primary role in the photocatalysis degradation of pollutants.•Ag-gC3N4/ZnO exhibited excellent stability and outstanding reusability.
Abstract
Photocatalytic formation of hydrocarbons using solar energy via artificial photosynthesis is a highly desirable renewable-energy source for replacing conventional fossil fuels. Using an
l
...-cysteine-based hydrothermal process, here we synthesize a carbon-doped SnS
2
(SnS
2
-C) metal dichalcogenide nanostructure, which exhibits a highly active and selective photocatalytic conversion of CO
2
to hydrocarbons under visible-light. The interstitial carbon doping induced microstrain in the SnS
2
lattice, resulting in different photophysical properties as compared with undoped SnS
2
. This SnS
2
-C photocatalyst significantly enhances the CO
2
reduction activity under visible light, attaining a photochemical quantum efficiency of above 0.7%. The SnS
2
-C photocatalyst represents an important contribution towards high quantum efficiency artificial photosynthesis based on gas phase photocatalytic CO
2
reduction under visible light, where the in situ carbon-doped SnS
2
nanostructure improves the stability and the light harvesting and charge separation efficiency, and significantly enhances the photocatalytic activity.
Abstract
Ascertaining the function of in-plane intrinsic defects and edge atoms is necessary for developing efficient low-dimensional photocatalysts. We report the wireless photocatalytic CO
2
...reduction to CH
4
over reconstructed edge atoms of monolayer 2H-WSe
2
artificial leaves. Our first-principles calculations demonstrate that reconstructed and imperfect edge configurations enable CO
2
binding to form linear and bent molecules. Experimental results show that the solar-to-fuel quantum efficiency is a reciprocal function of the flake size. It also indicates that the consumed electron rate per edge atom is two orders of magnitude larger than the in-plane intrinsic defects. Further, nanoscale redox mapping at the monolayer WSe
2
–liquid interface confirms that the edge is the most preferred region for charge transfer. Our results pave the way for designing a new class of monolayer transition metal dichalcogenides with reconstructed edges as a non-precious co-catalyst for wired or wireless hydrogen evolution or CO
2
reduction reactions.
An electrochemical capacitor configuration extends its operational potential window by leveraging diverse charge storage mechanisms on the positive and negative electrodes. Beyond harnessing ...capacitive, pseudocapacitive, or Faradaic energy storage mechanisms and enhancing electrochemical performance at high rates, achieving a balance of stored charge across electrodes poses a significant challenge over a wide range of charge-discharge currents or sweep rates. Consequently, fabricating hybrid and asymmetric supercapacitors demands precise electrochemical evaluations of electrode materials and the development of a reliable methodology. This work provides an overview of fundamental aspects related to charge-storage mechanisms and electrochemical methods, aiming to discern the contribution of each process. Subsequently, the electrochemical properties, including the working potential windows, rate capability profiles, and stabilities, of various families of electrode materials are explored. It is then demonstrated, how charge balancing between electrodes falters across a broad range of charge-discharge currents or sweep rates. Finally, a methodology for achieving charge balance in hybrid and asymmetric supercapacitors is proposed, outlining multiple conditions dependent on loaded mass and charge-discharge current. Two step-by-step tutorials and model examples for applying this methodology are also provided. The proposed methodology is anticipated to stimulate continued dialogue among researchers, fostering advancements in achieving stable and high-performance supercapacitor devices.
Abstract
Most chemical vapor deposition methods for transition metal dichalcogenides use an extremely small amount of precursor to render large single-crystal flakes, which usually causes low ...coverage of the materials on the substrate. In this study, a self-capping vapor-liquid-solid reaction is proposed to fabricate large-grain, continuous MoS
2
films. An intermediate liquid phase-Na
2
Mo
2
O
7
is formed through a eutectic reaction of MoO
3
and NaF, followed by being sulfurized into MoS
2
. The as-formed MoS
2
seeds function as a capping layer that reduces the nucleation density and promotes lateral growth. By tuning the driving force of the reaction, large mono/bilayer (1.1 mm/200 μm) flakes or full-coverage films (with a record-high average grain size of 450 μm) can be grown on centimeter-scale substrates. The field-effect transistors fabricated from the full-coverage films show high mobility (33 and 49 cm
2
V
−1
s
−1
for the mono and bilayer regions) and on/off ratio (1 ~ 5 × 10
8
) across a 1.5 cm × 1.5 cm region.
A simple one‐step electroplating route is proposed for the synthesis of novel iron oxyhydroxide lepidocrocite (γ‐FeOOH) nanosheet anodes with distinct layered channels, and the microstructural ...influence on the pseudocapacitive performance of the obtained γ‐FeOOH nanosheets is investigated via in situ X‐ray absorption spectroscopy (XAS) and electrochemical measurement. The in situ XAS results regarding charge storage mechanisms of electrodeposited γ‐FeOOH nanosheets show that a Li+ can reversibly insert/desert into/from the 2D channels between the FeO6 octahedral subunits depending on the applied potential. This process charge compensates the Fe2+/Fe3+ redox transition upon charging–discharging and thus contributes to an ideal pseudocapacitive behavior of the γ‐FeOOH electrode. Electrochemical results indicate that the γ‐FeOOH nanosheet shows the outstanding pseudocapacitive performance, which achieves the extraordinary power density of 9000 W kg−1 with good rate performance. Most importantly, the asymmetric supercapacitors with excellent electrochemical performance are further realized by using 2D MnO2 and γ‐FeOOH nanosheets as cathode and anode materials, respectively. The obtained device can be cycled reversibly at a maximum cell voltage of 1.85 V in a mild aqueous electrolyte, further delivering a maximum power density of 16 000 W kg−1 at an energy density of 37.4 Wh kg−1.
The simplified architecture and the sole use of iron oxyhydroxide lepidocrocite (γ‐FeOOH) nanosheet anodes leads to a new class of entirely charge storage devices exhibiting the extraordinary power density of 9000 W kg−1 with good rate performance. Notably, a maximum power density of 16 000 W kg−1 at an energy density of 37.4 Wh kg−1 is performed through MnO2 NS‐CC//FeOOH NS‐CC hybrid supercapacitors.
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