Dynamic Control of Asymmetric Charge Distribution for Electrocatalytic Urea Synthesis.

Constructing dual catalytic sites with charge density differences is an efficient way to promote urea electrosynthesis from parallel NO 3 - ${\mathrm{NO}}_3^ - $ and CO2 reduction yet still challenging in static system. Herein, a dynamic system is constructed by precisely controlling the asymmetric charge density distribution in an Au-doped coplanar Cu7 clusters-based 3D framework catalyst (Au@cpCu7CF). In Au@cpCu7CF, the redistributed charge between Au and Cu atoms changed periodically with the application of pulse potentials switching between -0.2 and -0.6 V and greatly facilitated the electrosynthesis of urea. Compared with the static condition of pristine cpCu7CF (FEurea = 5.10%), the FEurea of Au@cpCu7CF under pulsed potentials is up to 55.53%. Theoretical calculations demonstrated that the high potential of -0.6 V improved the adsorption of *HNO2 and *NH2 on Au atoms and inhibited the reaction pathways of by-products. While at the low potential of -0.2 V, the charge distribution between Au and Cu atomic sites facilitated the thermodynamic C-N coupling step. This work demonstrated the important role of asymmetric charge distribution under dynamic regulation for urea electrosynthesis, providing a new inspiration for precise control of electrocatalysis.

Development of chitosan/polycaprolactone-thymol Janus films with directional transport and antibacterial properties for meat preservation.

Reducing contamination from percolate is critical to the preservation of foods with high water content, such as pork. This study aims to develop a novel active packaging material for meat preservation by precisely controlled dual-channel one-step electrospinning. Compared to traditional strategies of preparing Janus films, this method allows for greater flexibility and efficiency. The structure and properties of the Janus film are characterized by scanning electron microscopy (SEM), water contact angle (WCA), directional liquid transport investigation, Thymol release and permeation features, and biocompatibility evaluation. Moreover, the Janus film is applied to the packaging of pork with modified atmosphere packaging to demonstrate its practical application prospects in the food active packaging field. The results revealed that the two sides of the film showed completely different wettability, and the change rate of WCA increased with the increase of the scale of hydrophilic fibers. The permeation features of thymol loaded in the film was consistent with the results of antibacterial properties and biocompatibility assessment. Moreover, the Janus film can effectively prolong the shelf life, improve the quality and safety of the pork.