Exploring cheap and stable electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) is now the key issue for the large-scale application of fuel cells, especially polymer electrolyte ...membrane fuel cells. The recent emergence of Fe (or Co)/N/C catalysts has created tremendous opportunities for the development of non-precious metal catalysts for ORR in acidic media and thus presents great potential in the application of fuel cells. In this review, we summarize the recent advances in the Fe (or Co)/N/C catalysts for ORR in acidic media that have demonstrated comparable activity to the commercial Pt catalyst. The synthesis, structural characterization and underlying mechanism of Fe (or Co)/N/C catalysts are discussed. In addition, we highlight the interesting microstructures of the active site, new synthesis approaches, and the catalytic performances tuned by nonmetal heteroatom dopants. Finally, perspectives on the challenges and future opportunities are also discussed.
Exploring cheap and stable electrocatalysts to replace Pt for the oxygen reduction reaction (ORR) is significant for the large-scale application of fuel cells, especially in polymer electrolyte membrane fuel cells. In this paper, we have briefly reviewed the recent advances in the Fe (or Co)/N/C ORR catalysts in acidic medium including their preparation, structural characterization and related mechanism.
Achieving homogeneous phase transition and uniform charge distribution is essential for good cycle stability and high capacity when phase conversion materials are used as electrodes. Herein, we show ...that chemical lithiation of bulk 2H-MoS2 distorts its crystalline domains in three primary directions to produce mosaic-like 1T′ nanocrystalline domains, which improve phase and charge uniformity during subsequent electrochemical phase conversion. 1T′-Li x MoS2, a macroscopic dense material with interconnected nanoscale grains, shows excellent cycle stability and rate capability in a lithium rechargeable battery compared to bulk or exfoliated-restacked MoS2. Transmission electron microscopy studies reveal that the interconnected MoS2 nanocrystals created during the phase change process are reformable even after multiple cycles of galvanostatic charging/discharging, which allows them to play important roles in the long term cycling performance of the chemically intercalated TMD materials. These studies shed light on how bulk TMDs can be processed into quasi-2D nanophase material for stable energy storage.
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IJS, KILJ, NUK, PNG, UL, UM
One of the most common problems with sulfide solid-state electrolytes is weak water stability. We report a re-sintering method to recover the ionic conductivity of argyrodite Li5.4PS4.4Cl1.6 ...solid-state electrolyte, which has been exposed to moisture for 10 h, from 1.06 to 6.97 mS cm−1.
The strong π-π interactions in the stacking layers of two-dimensional covalent organic frameworks (2D-COFs), together with rotationally labile imine linkages, make most of the solid state ...imine-linked COFs non-fluorescent due to fluorescence quenching processes. Here, we report the successful synthesis of highly photoluminescent imine-based 2D-COFs by integrating a non-planar building unit with a pyrene-based unit and transforming the COF into spherical, sub-micron particles. High photoluminescence quantum yields (PLQY) were achieved with COF sub-micron particles dispersed in organic solvents. The as-prepared COF sub-micron particles can be used as a chemical sensor for the detection of explosive chemicals, with high sensitivity and selectivity (up to ppm level).
Two-dimensional ferroelectrics is attractive for synaptic device applications because of its low power consumption and amenability to high-density device integration. Here, we demonstrate that tin ...monosulfide (SnS) films less than 6 nm thick show optimum performance as a semiconductor channel in an in-plane ferroelectric analogue synaptic device, whereas thicker films have a much poorer ferroelectric response due to screening effects by a higher concentration of charge carriers. The SnS ferroelectric device exhibits synaptic behaviors with highly stable room-temperature operation, high linearity in potentiation/depression, long retention, and low cycle-to-cycle/device-to-device variations. The simulated device based on ferroelectric SnS achieves ∼92.1% pattern recognition accuracy in an artificial neural network simulation. By switching the ferroelectric domains partially, multilevel conductance states and the conductance ratio can be obtained, achieving high pattern recognition accuracy.
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Although potassium-ion batteries (KIBs) are potentially alternative energy storage systems to lithium-ion batteries (LIBs), only few organic materials can be used as candidate electrodes for KIBs. ...Herein, we synthesized a class of carbonyl-based organic polymers including two 1D linear polymers, namely polyimide (PI) and polyquinoneimide (PQI), and a 2D conjugated microporous polymer (PI-CMP) as stable organic cathode materials for KIBs. The investigation of their electrochemical performance revealed the structure-property relationship. For instance, the direct connection between two electrochemical active organic molecules could increase the initial capacity; however, the tight distribution of potassiated carbonyl groups might cause rapid capacity fading. In addition, the extended π-conjugation could improve the cycling stability and rate performance. Furthermore, the redox mechanisms with potassium have been fully investigated utilizing FTIR, XPS measurements and DFT calculations, suggesting that the carbonyl group is the potassium-ion binding site with excellent reversibility for KIBs.
Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for ...achieving highly stable and selective catalysis. Here we demonstrate that 1T'-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide. The confinement of platinum nanoparticles within the molybdenum disulfide layered structure leads to enhanced hydrogen evolution reaction activity and stability compared to catalysts dispersed on carbon support. In particular, the inner platinum surface is accessible to charged species like proton and metal ions, while blocking poisoning by larger sized pollutants or neutral molecules. This points a way forward for using bulk intercalated compounds for energy related applications.
Niobium doped lithium titanate with the composition of Li
4Ti
4.95Nb
0.05O
12 has been prepared by a sol–gel method. X-ray diffraction (XRD) and scanning electron microscope (SEM) are employed to ...characterize the structure and morphology of Li
4Ti
4.95Nb
0.05O
12. The Li
4Ti
4.95Nb
0.05O
12 electrode presents a higher specific capacity and better cycling performance than the Li
4Ti
5O
12 electrode prepared by the similar process. The Li
4Ti
4.95Nb
0.05O
12 exhibits an excellent rate capability with a reversible capacity of 135
mAh
g
−1 at 10
C, 127
mAh
g
−1 at 20
C and even 80
mAh
g
−1 at 40
C. Electrical resistance measurement and electrochemical impedance spectra (EIS) reveal that the Li
4Ti
4.95Nb
0.05O
12 exhibits a higher electronic conductivity and faster lithium-ion diffusivity than the Li
4Ti
5O
12, which indicates that niobium doped lithium titanate (Li
4Ti
4.95Nb
0.05O
12) is promising as a high rate anode for the lithium-ion batteries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The argyrodite-type Li7−xPS6−xClx (LPSC) solid electrolyte is a promising candidate for Ah-scale all-solid-state Li-ion batteries due to its high ionic conductivity of over 10 mS cm−1. Understanding ...the influences of scalable synthesis conditions on the material structure and performance of LPSC is critical in industrial production. Herein, electrochemical impedance spectroscopy (EIS) combined with the distribution of relaxation times (DRT) analysis method was first applied to demonstrate the structure-conductivity relationships for the superionic Li+ conduction in LPSC to determine the optimum sintering temperature. The DRT tool enables the specific quantification of the ultrahigh lithium-ion kinetics in LPSC bulk/grain boundaries, which cannot be revealed by conventional fitting Nyquist plots. Detailed structural characterizations, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), were conducted to assist in analyzing the structural changes in the bulk and grain boundaries of LPSC. Finally, the Li5.4PS4.4Cl1.6 solid electrolyte sintered at 480 °C delivered the purest phase with the highest Li+ conductivity due to the lowest amount of grain boundaries and the shortest intercage ion leap distance in the unit cell. Thus, a narrow sintering temperature window is determined for obtaining LPSC with optimized performance. This work provides a novel DRT-assisted analysis protocol for exploring the craft-structure-performance correlations in LPSC, which helps guide industrial production.
•Separation of bulk and grain boundary impedances in LPSC using the DRT tool.•Clarifying relations between lattice and bulk/grain boundary conductivities.•Optimizing temperature window for LPSC to achieve the highest conductivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highlights
Divalent magnesium ions as electrolyte additives are first used to improve the performance of vanadium-based cathodes for aqueous ZIBs.
Pre-adding magnesium ions into electrolytes provide ...an appropriate equilibrium balance between the dissolution and recombination of magnesium vanadates, thus suppress the continuous dissolution of active materials, and lead to a higher stability of the electrode.
The hybrid aqueous electrolytes with cost-effective ZnSO
4
and MgSO
4
salts show a better competitive prospective for the stationary grid-scale applications.
MgSO
4
is chosen as an additive to address the capacity fading issue in the rechargeable zinc-ion battery system of Mg
x
V
2
O
5
·nH
2
O//ZnSO
4
//zinc. Electrolytes with different concentration ratios of ZnSO
4
and MgSO
4
are investigated. The batteries measured in the 1 M ZnSO
4
−1
M MgSO
4
electrolyte outplay other competitors, which deliver a high specific capacity of 374 mAh g
−1
at a current density of 100 mA g
−1
and exhibit a competitive rate performance with the reversible capacity of 175 mAh g
−1
at 5 A g
−1
. This study provides a promising route to improve the performance of vanadium-based cathodes for aqueous zinc-ion batteries with electrolyte optimization in cost-effective electrolytes.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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