Chemically etched CeO2-x nanorods with abundant surface defects as effective cathode additive for trapping lithium polysulfides in Li-S batteries

FeS2 deposited on 3D-printed carbon microlattices as free-standing electrodes for lithium-ion batteries

We introduce free-standing FeS2/carbon microlattice composites as electrodes for lithium-ion batteries through 3D printing. The computer-aided design allows for any shape. The microlattice features aligned microchannels, promoting ion transfer, while the carbon skeleton facilitates electron transfer. Overall, this study shows 3D printing is highly promising in advancing sustainable energy applications.

Low-Temperature Plasma-Assisted Catalytic Dry Reforming of Methane over CeO2 Nanorod-Supported NiO Catalysts in a Dielectric Barrier Discharge Reactor

Nonthermal plasma (NTP)-assisted catalytic dry reforming of methane (DRM) is considered a powerful single-stage reaction mechanism because of its ability to activate normally stable CO2 and CH4 at a low temperature under ambient conditions. The thermodynamic barrier of DRM requires a high operating temperature (>700 °C), which can be reduced by nonequilibrium plasma. Herein, we present a method for the wet-impregnation synthesis of CeO2 nanorod (NR)-supported 5 and 15 wt % NiO catalysts for efficient NTP-promoted DRM with an applied power in the range of 24.9-25.8 W (frequency: 20 kHz), a CH4:CO2 feed gas ratio of 100:250 sccm, and a total flow rate of 350 sccm. The presence of NTP dramatically increased the reaction activity, even at 150 °C, which is usually inaccessible for thermally catalyzed DRM. The CH4 and CO2 conversion reaches a maximum of 66 and 48%, respectively, at 500 °C with the 15 wt % NiO/CeO2 NR catalyst, which are much higher than the values obtained for the 5 wt % NiO/CeO2 NR catalyst under the same conditions. According to the X-ray photoelectron spectroscopy profile for 15 wt % NiO/CeO2 NR, a higher concentration of NiO on CeO2 increases the proportion of Ce3+ in the catalyst, suggesting enhanced oxygen vacancy concentration with an increased amount of NiO loading. Additionally, a higher NiO loading promotes a higher rate of replacement of Ce4+ with Ni2+, which generates more oxygen vacancies due to the induced charge imbalance and lattice distortion within the CeO2 lattice. As a result, it can be inferred that the incorporation of Ni ions into the CeO2 structure resulted in inhibited growth of CeO2 crystals due to the creation of a NixCe1-xO2-α solid solution and the production of oxygen vacancies.

Semi-Ionic C-F bond enabling fluorinated carbons rechargeable as Li-ion batteries cathodes

Fluorinated carbon (CF_x) cathodes possess the highest theoretical energy density among lithium primary batteries. However, achieving reversibility in CF_x remains a significant challenge. This work employs a high-voltage sulfolane electrolyte and achieves a highly reversible CF_x cathodes in lithium-ion batteries (LIBs) via fine modification of the C-F bond character. The improved reversibility of CF_x originates from the semi-ionic CF_x phase, with a superior bond length and weaker bond energy than a covalent bond. This characteristic significantly mitigates the challenges encountered during the charging process. We screen and identify the fluorinated graphene CF_1.12 as a suitable cathode, providing an appropriate fluorine content and sufficient semi-ionic C-F bonds for rechargeable LIBs. This fluorinated graphene CF_1.12 exhibits an initial discharge specific capacity of 814 mAh g^-1 and a reversible discharge specific capacity of 350 mAh g^-1. This work provides a new clue for chemical bond regulation studies and provides insights into stimulating reversibility of primary-cell cathodes.

Ultrafast microwave synthesis of MoTe2@graphene composites accelerating polysulfide conversion and promoting Li2S nucleation for high-performance Li-S batteries

In this report, MoTe₂ nanosheets were grown on highly conductive graphene support through a simple and ultrafast microwave-assisted chemical coupling and heating method to develop hybrid sulfur host materials for Li-S batteries. MoTe₂ nanosheets with superb electrocatalytic activity combined with highly conductive graphene form a nano reservoir for containing elemental sulfur, intermediate polysulfide species, discharge product Li₂S, and accelerating the electron transfer. Accordingly, the Li-S battery with the MoTe₂@graphene@carbon cloth electrode exhibited a high initial discharge capacity of 1246 mAh g^-1 at 0.2C for the first galvanostatic cycle, good cycle stability (98.7% capacity retention after 100 cycles at 0.2C) and superb rate performance. The synergistic effect of the chemical affinity and superior electrocatalytic capability of polar MoTe_2, along with the effective physical confinement by graphene and free-standing carbon cloth, provides a promising way to design host materials to mitigate the shuttling effect in rechargeable Li-S batteries.

Adsorption-catalysis design with cerium oxide nanorods supported nickel-cobalt-oxide with multifunctional reaction interfaces for anchoring polysulfides and accelerating redox reactions in lithium sulfur battery

The charge and discharge working mechanisms in lithium sulfur batteries contain multi-step complex reactions involving two-electron transfer and multiple phase transformations. The dissolution and diffusion of lithium polysulfides cause a huge loss of active material and fast capacity decay, preventing the practical use of lithium sulfur batteries. Herein, CeO₂ nanorods supported bimetallic nickel cobalt oxide (NiCo₂O_x) was investigated as a cathode host material for lithium sulfur batteries, which can provide adsorption-catalysis dual synergy to restrain the shuttle of polysulfides and stimulate rapid redox reaction for the conversion of polysulfides. The polar CeO₂ nanorods with abundant surface defects exhibit chemisorption towards lithium polysulfides and the excellent electrocatalytic activity of NiCo₂O_x nanoclusters can rev up the chain transformation of lithium polysulfides. The electrochemical results show that the battery with NiCo₂O_x/CeO₂ nanorods can demonstrate high discharge capacity, stable cycling, low voltage polarization and high sulfur utilization. The battery with NiCo₂O_x/CeO₂ nanorods unveils a high specific capacity of 1236 mAh g^-1 with a very low capacity fading of 0.09% per cycle after 100 cycles at a 0.2C current rate. Moreover, the excellent performance with high sulfur loading (>5 mg cm^-2) verifies a huge promise for future commercial applications.

Ultrasonically assisted surface modified CeO2 nanospindle catalysts for conversion of CO2 and methanol to DMC

This study developed a facile and effective approach to engineer the surface properties of cerium oxide (CeO2) nanospindle catalysts for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. CeO2 nanospindles were first prepared by a simple precipitation method followed by wet chemical redox etching with sodium borohydride (NaBH4) under high intensity ultrasonication (ultrasonic horn, 20 kHz, 150 W/cm2). The ultrasonically assisted surface modification of the CeO2 nanospindles in NaBH4 led to particle collisions and surface reduction that resulted in an increase in the number of surface-active sites of exposed Ce3+ and oxygen vacancies. The surface modified CeO2 nanospindles showed an improvement of catalytic activity for DMC formation, yielding 17.90 mmol·gcat-1 with 100 % DMC selectivity. This study offers a simple and effective method to modify a CeO2 surface, and it can further be applied for other chemical activities.