Search

N2-plasma bombardment allows the large-area fabrication of high 1T phase N,Pt-doped MoS2 nanosheets with prominent alkaline HER activity.

All-solid-state sodium batteries (ASSSBs) are attractive alternatives to lithium-ion batteries for grid-scale energy storage due to their high safety and ubiquitous distribution of Na sources. A critical component for ASSSB is sodium-ion conducting solid-state electrolyte (SSE). Here, we report a high-performance sodium-ion SSE with the recently developed bulk interfacial superionic conductor (BISC) concept. The ionic conductivity and areal conductance of the Na+ BISC at 25 °C reaches 6.5 × 10-4 S cm-1 and 260 mS cm-2, respectively. Using NaxCo0.7Mn0.3O2 (x ≈ 1.0, NaCMO) as the cathode active material, all-solid-state Na||NaCMO batteries exhibiting small overpotential and ∼180 cycle life are demonstrated under room temperature. This approach may also be used to prepare other metal ion, such as Mg2+, Al3+, and K+, based all-solid-state batteries.

Multimetallic nanoparticles are an important class of catalysts with significant technological potential. In this work, trimetallic PtPdCu nanoparticles synthesized via a facile one-pot colloidal m...

Effective adsorption and speedy surface reactions are vital requirements for efficient active sites in catalysis, but it remains challenging to maximize these two functions simultaneously. We present a solution to this issue by designing a series of atom-pair catalytic sites with tunable electronic interactions. As a case study, NO selective reduction occurring on V

Ferroelectric barium titanate nanoparticles (BTO NPs) may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors. While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade, the majority of the investigation was carried out in thin-film materials; therefore, the doping effect on nanoparticles remains unclear. Especially, doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled. In this work, we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), integrated differential phase contrast (iDPC)-STEM, and energy dispersive X-ray spectroscopy (EDX) mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles. Powder X-ray diffraction (PXRD) results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase, but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles. Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.

P2-Na0.67Ni0.33Mn0.67O2 presents high working voltage with a theoretical capacity of 173 mAh g-1. However, the lattice oxygen on the particle surface participates in the redox reactions when the material is charged over 4.22 V. The resulting oxidized oxygen aggravates the electrolyte decomposition and transition metal dissolution, which cause severe capacity decay. The commonly reported cation substitution methods enhance the cycle stability by suppressing the high voltage plateau but lead to lower average working voltage and reduced capacity. Herein, we stabilized the lattice oxygen by a small amount of Sn substitution based on the strong Sn-O bond without sacrificing the high voltage performance and further protected the particle surface by polypyrrole (PPy) coating. The obtained Na0.67Ni0.33Mn0.63Sn0.04O2@PPy (3.3 wt %) composite showed excellent cycling stability with a reversible capacity of 137.6 (10) and 120.0 mAh g-1 (100 mA g-1) with a capacity retention of 95% (10 mA g-1, 50 cycles) and 82.5% (100 mA g-1, 100 cycles), respectively. The present work indicates that slight Sn substitution combined with PPy coating could be an effective approach to achieving superior cycling stability for high-voltage layered transition metal oxides.

The electrocatalytic nitrogen reduction reaction (NRR) on metal-free catalysts is an attractive alternative to the industrial Haber-Bosch process. However, the state-of-the-art metal-free electrocatalysts still suffer from low Faraday efficiencies and low ammonia yields. Herein, we present a molecular design strategy to develop a defective boron carbon nitride (BCN) catalyst with the abundant unsaturated B and N atoms as Lewis acid and base sites, which upgrades the catalyst from a single "Lewis acid catalysis" to "frustrated Lewis pairs (FLPs) catalysis."

Guided by in situ synchrotron X-ray diffraction (SXRD) measurements and quantitative analysis, we identified and synthesized a new type of lithium nickel oxide as a cathode material for Li-ion batteries. This compound is a composition of two crystallographic components: a major stoichiometric layer-structured phase, LiNiO2, and a minor Li-containing disordered rock-salt phase, LiδNi1-δO, both embedded in the same cubic close-packed oxygen lattice. The LiNiO2|LiδNi1-δO composite, when used as the active material in a cathode, delivers high energy density, superior rate capability, and long-term cycling stability owing to its unique structural configuration.

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H 2 O 2 ) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H 2 O 2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H 2 O 2 , potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H 2 O 2 and TS-1, while allowing for considerable process intensification.

The ammoximation of cyclohexanone using preformed hydrogen peroxide (H

Petroleum is one of the most important natural resources for human beings, while the contained sulfur heteroatoms lead to a series of problems1. Therefore, a desulfurization process to reduce sulfur content is mandatory for clean petroleum utilization. Hydrodesulfurization is currently mature in industry, while this process is costly, energy intensive and environmentally unfriendly due to CO2 emission and H2S production2,3. Alternative cost-effective desulfurization process with environmentally benign sulfur-containing products remains unreported. Here we demonstrate that the desulfurization of a heavy oil model compound dibenzothiophene can be successfully achieved under methane environment over creatively designed dual catalyst system, generating a new sulfur-containing product CS2. Control experiments indicate that the presence of methane as well as catalyst components for direct desulfurization and methane activation are all required. The reaction process is better understood by extensive evidences from isotope labeling experiments, catalyst and product characterizations, density functional theory calculations and verification experiments, based on which a reasonable catalytic mechanism is proposed. It is found that methane-assisted desulfurization requires more stringent conditions, where sulfur vacancy abundance, methane activation capability and surface sulfur transfer are all indispensable. This study pioneers a transformational desulfurization route, which is more economically and environmentally attractive for petroleum processing industry.

Bimetallic Pd-Fe catalysts supported on TiO2 are shown to be highly effective toward the selective oxidation of benzyl alcohol to benzaldehyde via the in situ production of H2O2 from molecular H2 and O2, under conditions where no reaction is observed with molecular O2 alone. The rate of benzyl alcohol oxidation observed over supported Pd-Fe nanoparticles is significantly higher than those of either Pd-Au or Pd-only analogues. This enhanced activity can be attributed to the bifunctionality of the Pd-Fe catalyst to both synthesize H2O2 and catalyze the production of oxygen-based radical specie,s as indicated by an electron paramagnetic resonance analysis. Further studies also reveal the noninnocent nature of the solvent, resulting in the propagation of radical generation pathways.

P2-Na

Ni-rich layered oxide cathode materials, such as LiNi0.83Co0.12Mn0.05O2 (NCM811), exhibit high specific capacity and low cost, and become cathode material preference of high-energy-density Li-ion batteries. However, these cathode materials are not stable and will form Li-poor reconstructed layers and alkaline compounds (Li2CO3, LiOH) on the surface during the storage and processing in humid air, resulting in serious deterioration of electrochemical properties. During the past two decades, the consensus on the surface instability mechanism during humid air storage has not been reached. The main controversy focuses on the unstable octahedron mechanism and the Li/H exchange mechanism. Herein, we investigate the instability mechanism in the humid air by conducting scanning electronic microscopy, scanning transmission electron microscopy, and x-ray photoelectron spectroscopy analysis on NCM811 samples stored in designed atmospheres, etc., and realize that the surface instability of the NCM811 during storage should be mainly originated from Li/H exchange when it contacts with moisture.

NaTaO3/reduced graphene oxide (RGO) composite were prepared via a two-step hydrothermal method. The as-prepared NaTaO3/RGO composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and X-ray photoelectron spectroscopy (XPS). The results indicated the reduction of graphene oxide and the chemical bonding between RGO and NaTaO3 are achieved simultaneously. As a result, NaTaO3/RGO composite possessed efficient charge separation properties. Hence, in the photocatalytic measurement toward the H2 production from an aqueous Na2S/Na2SO3 solution under UV illumination, a significant improvement in the H2 production rate was observed over NaTaO3/RGO composite, compared to the pure NaTaO3 and mechanically mixed NaTaO3-RGO composite with the same RGO content. In particular, the photocatalytic H2 production rate over NaTaO3/2%RGO with RGO content of 2 wt% was 3.82 times higher than that of pure NaTaO3. Moreover, the photocatalytic hydrogen production performance of NaTaO3/2%RGO was rather stable. A plausible electron transfer mechanism was proposed to discuss the improved photocatalytic H2 production performance.