Deep Potential Molecular Dynamics Study of Propane Oxidative Dehydrogenation

Oxidative dehydrogenation (ODH) of light alkanes is a key process in the oxidative conversion of alkanes to alkenes, oxygenated hydrocarbons, and COx (x = 1,2). Understanding the underlying mechanisms extensively is crucial to keep the ODH under control for target products, e.g., alkenes rather than COx, with minimal energy consumption, e.g., during the alkene production or maximal energy release, e.g., during combustion. In this work, deep potential (DP), a neural network atomic potential developed in recent years, was employed to conduct large-scale accurate reactive dynamic simulations. The model was trained on a sufficient data set obtained at the density functional theory level. The intricate reaction network was elucidated and organized in the form of a hierarchical network to demonstrate the key features of the ODH mechanisms, including the activation of propane and oxygen, the influence of propyl reaction pathways on the propene selectivity, and the role of rapid H2O2 decomposition for sustainable and efficient ODH reactions. The results indicate the more complex reaction mechanism of propane ODH than that of ethane ODH and are expected to provide insights in the ODH catalyst optimization. In addition, this work represents the first application of deep potential in the ODH mechanistic study and demonstrates the ample advantages of DP in the study of mechanism and dynamics of complex systems

Interconnected Nanoflake Network Derived from a Natural Resource for High-Performance Lithium-Ion Batteries

Numerous natural resources have a highly interconnected network with developed porous structure, so enabling directional and fast matrix transport. Such structures are appealing for the design of efficient anode materials for lithium-ion batteries, although they can be challenging to prepare. Inspired by nature, a novel synthesis route from biomass is proposed by using readily available auricularia as retractable support and carbon coating precursor to soak up metal salt solution. Using the swelling properties of the auricularia with the complexation of metal ions, a nitrogen-containing MnO@C nanoflake network has been easily synthesized with fast electrochemical reaction dynamics and a superior lithium storage performance. A subsequent carbonization results in the in situ synthesis of MnO nanoparticles throughout the porous carbon flake network. When evaluated as an anode material for lithium-ion batteries, an excellent reversible capacity is achieved of 868 mA h g^–1 at 0.2 A g^–1 over 300 cycles and 668 mA h g^–1 at 1 A g^–1 over 500 cycles, indicating a high tolerance to the volume expansion. The approach investigated opens up new avenues for the design of high performance electrodes with highly cross-linked nanoflake structures, which may have great application prospects

Engineering of Hollow Core–Shell Interlinked Carbon Spheres for Highly Stable Lithium–Sulfur Batteries

We report engineered hollow core–shell interlinked carbon spheres that consist of a mesoporous shell, a hollow void, and an anchored carbon core and are expected to be ideal sulfur hosts for overcoming the shortage of Li–S batteries. The hollow core–shell interlinked carbon spheres were obtained through solution synthesis of polymer spheres followed by a pyrolysis process that occurred in the hermetical silica shell. During the pyrolysis, the polymer sphere was transformed into the carbon core and the carbonaceous volatiles were self-deposited on the silica shell due to the blocking effect of the hermetical silica shell. The gravitational force and the natural driving force of lowering the surface energy tend to interlink the carbon core and carbon/silica shell, resulting in a core–shell interlinked structure. After the SiO₂ shell was etched, the mesoporous carbon shell was generated. When used as the sulfur host for Li–S batteries, such a hierarchical structure provides access to Li⁺ ingress/egress for reactivity with the sulfur and, meanwhile, can overcome the limitations of low sulfur loading and a severe shuttle effect in solid carbon-supported sulfur cathodes. Transmission electron microscopy and scanning transmission electron microscopy images provide visible evidence that sulfur is well-encapsulated in the hollow void. Importantly, such anchored-core carbon nanostructures can simultaneously serve as a physical buffer and an electronically connecting matrix, which helps to realize the full potential of the active materials. Based on the many merits, carbon–sulfur cathodes show a high utilization of sulfur with a sulfur loading of 70 wt % and exhibit excellent cycling stability (<i>i.e.</i>, 960 mA h g^–1 after 200 cycles at a current density of 0.5 C)

Incorporating Sulfur Inside the Pores of Carbons for Advanced Lithium–Sulfur Batteries: An Electrolysis Approach

We have developed an electrolysis approach that allows effective and uniform incorporation of sulfur inside the micropores of carbon nanosheets for advanced lithium–sulfur batteries. The sulfur–carbon hybrid can be prepared with a 70 wt % sulfur loading, in which no nonconductive sulfur agglomerations are formed. Because the incorporated sulfur is electrically connected to the carbon matrix in nature, the hybrid cathode shows excellent electrochemical performance, including a high reversible capacity, good rate capability, and good cycling stability, as compared to one prepared using the popular melt-diffusion method

Enhancing Ethanol Coupling to Produce Higher Alcohols by Tuning H₂ Partial Pressure over a Copper-Hydroxyapatite Catalyst

Catalytic upgrading of ethanol, as a platform molecule from biomass to higher alcohols (C4–12), is a low-carbon route for value-added chemical production. However, the products are generally obtained in low selectivity due to the uncontrollable reactivity of intermediates that cause a complex reaction network. In this study, we show that unsaturated intermediates of aldehydes can be rapidly hydrogenated by surface hydrogen species during the ethanol upgrading process, thereby greatly inhibiting the cyclization reaction of aldehydes. Specifically, the product distributions on the Cu-hydroxyapatite (Cu-HAP) catalyst shift stepwise to higher alcohols from aromatic oxygenates with the partial pressure of hydrogen increasing from 0 to 95 kPa. Kinetic measurements and in situ ethanol infrared results indicated that the intermediates during this process are acetaldehyde and 2-butenal. Combined with physical structure and chemical state analysis of the catalyst, we found that Cu sites catalyze the hydrogenation of the CC bond of 2-butenal under a hydrogen atmosphere. The C–C coupling of ethanol to higher alcohols over Cu-HAP follows the Guerbet mechanism. In comparison, on bare HAP, n-butanol is formed as a primary product even though little amount of acetaldehyde was detected, indicating that ethanol proceeds mainly in a direct coupling process to yield higher alcohols. This study introduces an efficient ethanol valorization approach that is enabled by subtle control of the intermediate conversion over the Cu-HAP catalyst by the hydrogen partial pressure

Diaminohexane-Assisted Preparation of Coral-like, Poly(benzoxazine)-Based Porous Carbons for Electrochemical Energy Storage

The assembly of commercial silica colloids in the presence of 1,6-diaminohexane and their subsequent encapsulation by poly­(benzoxazine) have been used to produce coral-like porous carbons. The pyrolysis of the polymer followed by the removal of the silica produces a carbon with a continuous skeleton that contains spherical medium-size pores as “reservoirs” with a structure similar to a bunch of grapes. The total volume and the diameter of the “reservoir” pores are tunable. The coral-like morphology and the pore structure of the carbons make them suitable for use as electrode materials for supercapacitors and lithium-ion batteries. As supercapacitor electrodes, they exhibit excellent long-term cycle stability (almost no capacitance fading after 20 000 cycles at a current density of 1 A g^–1) and good rate capability with capacitance retention of 88% (from 0.1 A g^–1 to 5 A g^–1). Meanwhile, as a matrix for the encapsulation of SnO₂ nanoparticles for Li-ion storage, the electrodes also show a high specific capacity and good cycling stability, i.e., 900 mA h g^–1 after 50 charge–discharge cycles. The good electrochemical performance of such carbons shows that they are promising candidate electrode materials for electrochemical energy storage

Cobalt Phthalocyanine–Graphene Oxide Nanocomposite: Complicated Mutual Electronic Interaction

Through the adsorption/intercalation of cobalt phthalocyanine (CoPc) onto/into graphene oxide (GO) layers, CoPc–GO nanocomposite was prepared via a simple solvent evaporation method driven by the electronic interaction between CoPc and GO. The interaction between GO and CoPc has been studied in detail by various methods. The result suggests that the interaction does not follow a simple donor–acceptor mode, but, instead, it is complicated two-way process including the transfer of electron from the graphitic domain to the adsorbed/intercalated CoPc, and a feedback from the Co ions through the ligand-like attacking of oxygen functional groups of GO to the central cobalt ions. The obtained structural hybrid materials have potential in the electrochemical detection of the compounded medicine

Thin Porous Alumina Sheets as Supports for Stabilizing Gold Nanoparticles

Thin porous alumina sheets have been synthesized using a lysine-assisted hydrothermal approach resulting in an extraordinary catalyst support that can stabilize Au nanoparticles at annealing temperatures up to 900 °C. Remarkably, the unique architecture of such an alumina with thin sheets (average thickness ∼15 nm and length 680 nm) and rough surface is beneficial to prevent gold nanoparticles from sintering. HRTEM observations clearly showed that the epitaxial growth between Au nanoparticles and alumina support was due to strong interfacial interactions, further explaining the high sinter-stability of the obtained Au/Al₂O₃ catalyst. Consequently, despite calcination at 700 °C, the catalyst maintains its gold nanoparticles of size predominantly 2 ± 0.8 nm. Surprisingly, catalyst annealed at 900 °C retained the highly dispersed small gold nanoparticles. It was also observed that a few gold particles (6–25 nm) were encapsulated by an alumina layer (thickness less than 1 nm) to minimize the surface energy, revealing a surface restructuring of the gold/support interface. As a typical and size-dependent reaction, CO oxidation is used to evaluate the performance of Au/Al₂O₃ catalysts. The results obtained demonstrated Au/Al₂O₃ catalyst calcined at 700 °C exhibited excellent activity with a complete CO conversion at ∼30 °C (<i>T</i>_100% = 30 °C), and even after calcination at 900 °C, the catalyst still achieved its <i>T</i>_50% at 158 °C. In sharp contrast, Au catalyst prepared using conventional alumina support shows almost no activity under the same preparation and catalytic test conditions

Monolithic Carbons with Tailored Crystallinity and Porous Structure as Lithium-Ion Anodes for Fundamental Understanding Their Rate Performance and Cycle Stability

A series of hierarchically multimodal (micro-, meso-/macro-) porous carbon monoliths with tunable crystallinity and architecture have been designedly prepared through a simple and effective gelation through a dual phase separation process and subsequent pyrolysis. Because of the magnificent structural characteristics, such as highly interconnected three-dimensional (3D) crystalline carbon framework with hierarchical pore channels, which ensure a fast electron transfer network and lithium-ion transport, the carbon anodes exhibit a good cycle performance and rate capability in lithium-ion cells. Importantly, a correlation between the electrochemical performances and their structural features of crystalline and textural parameters has been established for the first time, which may be of valid for better understanding of their rate performance and cycle stability

Using Hollow Carbon Nanospheres as a Light-Induced Free Radical Generator To Overcome Chemotherapy Resistance

Under evolutionary pressure from chemotherapy, cancer cells develop resistance characteristics such as a low redox state, which eventually leads to treatment failures. An attractive option for combatting resistance is producing a high concentration of produced free radicals <i>in situ</i>. Here, we report the production and use of dispersible hollow carbon nanospheres (HCSs) as a novel platform for delivering the drug doxorubicine (DOX) and generating additional cellular reactive oxygen species using near-infrared laser irradiation. These irradiated HCSs catalyzed sufficiently persistent free radicals to produce a large number of heat shock factor-1 protein homotrimers, thereby suppressing the activation and function of resistance-related genes. Laser irradiation also promoted the release of DOX from lysosomal DOX@HCSs into the cytoplasm so that it could enter cell nuclei. As a result, DOX@HCSs reduced the resistance of human breast cancer cells (MCF-7/ADR) to DOX through the synergy among photothermal effects, increased generation of free radicals, and chemotherapy with the aid of laser irradiation. HCSs can provide a unique and versatile platform for combatting chemotherapy-resistant cancer cells. These findings provide new clinical strategies and insights for the treatment of resistant cancers