Engineering a High-Loading Sub-4 nm Intermetallic Platinum-Cobalt Alloy on Atomically Dispersed Cobalt-Nitrogen-Carbon for Efficient Oxygen Reduction in Fuel Cells.

Developing a high-performance membrane electrode assembly (MEA) poses a formidable challenge for fuel cells, which lies in achieving both high metal loading and efficient catalytic activity concurrently for MEA catalysts. Here, we introduce a porous Co@NC carrier to synthesize sub-4 nm PtCo intermetallic nanocrystals, achieving an impressive Pt loading of 27 wt %. The PtCo-CoNC catalyst demonstrates exceptional catalytic activity and remarkable stability for the oxygen reduction reaction. Advanced characterization techniques and theoretical calculations emphasize the synergistic effect between PtCo alloys and single Co atoms, which enhances the desorption of the OH* intermediate. Furthermore, the PtCo-CoNC-based cathode delivers a high power density of 1.22 W cm-2 in the MEA test owing to the enhanced mass transport, which is verified by the simulation results of the O2 distributions and current density inside the catalyst layer. This study lays the groundwork for the design of efficient catalysts with practical applications in fuel cells.

SO2/NO2 Separation Driven by NO2 Dimerization on SSZ-13 Zeolite Membrane.

The molecular state is crucial for precise gas separation using a zeolite membrane, yet the state control remains a big challenge. Herein, we report a NO2 dimerization facilitated high performance SO2/NO2 separation on a SSZ-13 zeolite membrane. The NO2 dimerization is triggered by temperature and pressure to form N2O4 with big molecular size, and N2O4 diffusion into the zeolite pore is inhibited on the basis of size exclusion, leading to high separation selectivity. Consequently, SO2 rather than NO2 preferentially permeates through the SSZ-13 membrane with a high SO2 permeance of 2 × 10-7 mol m-2 s-1 Pa-1 and high SO2/NO2 separation factor of 22, ∼50-fold of that measured without dimerization. The dimerization effect for SO2/NO2 separation prevails in other small-pore zeolites such as NaA. This advanced function is revealed through membrane separation using single and mixture gases.

Separation of SO2 and NO2 with the Zeolite Membrane: Molecular Simulation Insights into the Advantageous NO2 Dimerization Effect.

NO2 and SO2, as valuable chemical feedstock, are worth being recycled from flue gases. The separation of NO2 and SO2 is a key process step to enable practical deployment. This work proposes SO2 separation from NO2 using chabazite zeolite (SSZ-13) membranes and provides insights into the feasibility and advantages of this process using molecular simulation. Grand canonical ensemble Monte Carlo and equilibrium molecular dynamics methods were respectively adopted to simulate the adsorption equilibria and diffusion of SO2, NO2, and N2O4 on SSZ-13 at varying Si/Al (1, 5, 11, 71, +∞), temperatures (248-348 K), and pressures (0-100 kPa). The adsorption capacity and affinity (SO2 > N2O4 > NO2) demonstrated strong competitive adsorption of SO2 based on dual-site interactions and significant reduction in NO2 adsorption due to dimerization in the ternary gas mixture. The simulated order of diffusivity (NO2 > SO2 > N2O4) on SSZ-13 demonstrated rapid transport of NO2, strong temperature dependence of SO2 diffusion, and the impermeability of SSZ-13 to N2O4. The membrane permeability of each component was simulated, rendering a SO2/NO2 membrane separation factor of 26.34 which is much higher than adsorption equilibrium (6.9) and kinetic (2.2) counterparts. The key role of NO2-N2O4 dimerization in molecular sieving of SO2 from NO2 was addressed, providing a facile membrane separation strategy at room temperature.

Tea (Camellia sinensis L.) flower polysaccharide attenuates metabolic syndrome in high-fat diet induced mice in association with modulation of gut microbiota.

There is a growing body of evidence suggesting that dietary polysaccharides play a crucial role in preventing metabolic syndrome (MetS) through their interaction with gut microbes. Tea (Camellia sinensis L.) flower polysacchride (TFPS) is a novel functional compound known for its diverse beneficial effects in both vivo and vitro. To further investigate the effects of TFPS on MetS and gut microbiota, and the possible association between gut microbiota and their activities, this study was carried out on mice that were fed a high-fat diet (HFD) and given oral TFPS at a dose of 400 and 800 mg/kg·body weight (BW)/d, respectively. TFPS treatment significantly mitigated HFD-induced MetS, evidenced by reductions in body weight, fat accumulation, plasma levels of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and pro-inflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and IL-1ß, along with an increase in plasma IL-10 levels. Furthermore, TFPS induced alterations in the diversity and composition of HFD-induced gut microbiota. Specifically, TFPS influenced the relative abundance of 11 genera, including Lactobacillus and Lactococcus, which showed strong correlations with metabolic improvements and likely contributed to the amelioration of MetS. In conclusion, TFPS exhibits promising prebiotic properties in preventing MetS and regulating gut microbiota.

Enantioselective [3 + 2] Cycloaddition of Vinylcyclopropanes with Alkenyl N-Heteroarenes Enabled by Palladium Catalysis.

The first catalytic enantioselective [3 + 2] cycloaddition reaction between vinylcyclopropanes and alkenyl N-heteroarenes in the presence of LiBr and a Pd(0)/SEGPHOS complex was developed. LiBr plays a key role in improving the reactivity of alkenyl N-heteroarenes as a mild Lewis acid.