Systematic studies of fission fragment kinetic energy distributions by Langevin simulations

Fission fluctuation-dissipation dynamics of heavy nuclei has been studied using Langevin Monte Carlo simulations. The covariant form of the fission transport equation and the coefficients related to it are investigated. To learn about the influence of the dynamics from the ground state to the saddle point on the kinetic energy distributions we have studied various systems and compared the calculations both starting from the ground state and from the saddle point. Both the mean total kinetic energy of the fission fragments and its variances can fit with the experimental values in terms of a finite neck radius as scission condition.This work was supported by the National Natural Science Foundation of China.     

Amine Coordinated Electron-Rich Palladium Nanoparticles for Electrochemical Hydrogenation of Benzaldehyde

Electrocatalytic hydrogenation (ECH) is a burgeoning strategy for the sustainable utilization of hydrogen. However, how to effectively suppress the competitive hydrogen evolution reaction (HER) is a big challenge to ECH catalysis. In this study, amine (NH₂ R)-coordinated Pd nanoparticles loaded on carbon felt (Pd@CF) as a catalyst is successfully synthesized by a one-step solvothermal reduction method using oleylamine as the reducing agent. An exceptional ECH reactivity on benzaldehyde is achieved on the optimal Pd@CF catalyst in terms of a high conversion (89.7%) and selectivity toward benzyl alcohol (89.8%) at −0.4 V in 60 min. Notably, the Faradaic efficiency for producing benzyl alcohol is up to 90.2%, much higher than that catalyzed by Pd@CF-without N-group (41.1%) and thecommercial Pd/C (20.9%). The excellent ECH performance of Pd@CF can be attributed to the enriched electrons on Pd surface resulted from the introduction of NH₂ R groups, which strengthens both the adsorption of benzaldehyde and the adsorbed hydrogen (H_ads) on Pd, preventing the combination of H_ads to form H₂, that is, inhibiting the HER. This study gives a new insight into design principles of highly efficient electrocatalysts for the hydrogenation of unsaturated aldehydes molecules.     

Toward Flexible Embodied Energy: Scale-Inspired Overlapping Lithium-Ion Batteries with High-Energy-Density and Variable Stiffness

High performance flexible batteries are essential ingredients for flexible devices. However, general isolated flexible batteries face critical challenges in developing multifunctional embodied energy systems, owing to the lack of integrative design. Herein, inspired by scales in creatures, overlapping flexible lithium-ion batteries (FLIBs) consisting of energy storage scales and connections using LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) and graphite electrodes are presented. The scale-dermis structure ensures a high energy density of 374.4 Wh L⁻¹ as well as a high capacity retention of 93.2% after 200 charge/discharge cycles and 40 000 bending times. A variable stiffness property is revealed that can be controlled by battery configurations and deformation modes. Furthermore, the overlapping FLIBs can be housed directly into the architecture of several flexible devices, such as robots and grippers, allowing to create multifunctionalities that go far beyond energy storage and include load-bearing and variable flexibility. This study broadens the versatility of FLIBs toward energy storage structure engineering of flexible devices.     

Light-Responsive Programmable Shape-Memory Soft Actuator Based on Liquid Crystalline Polymer/Polyurethane Network

Liquid crystalline polymers (LCPs), especially liquid crystalline elastomers (LCEs) can generate ultrahigh shape change amplitude but has lower mechanical strength. Although some attempts have been tried to improve the mechanical performance of LCE, there are still limitations including complicated fabrication and high actuation temperature. Here, a versatile method is reported to fabricate light-driven actuator by covalently cross-linking polyurethane (PU) into LCP networks (PULCN). This new scheme is distinct from the previous interpenetrating network strategy, the hydrogen bonds and covalent bonds are used in this study to improve the miscibility of non-liquid-crystalline PU and LCP materials and enhance the stability of the composite system. This material not only possesses the shape memory properties of PU but shows shape-changing behavior of LCPs. With a shrinkage ratio of 20% at the phase transition temperature, the prepared materials reached a maximum mechanical strength of 20 MPa, higher than conventional LCP. Meanwhile, the resulting film shows diverse and programmable initial shapes by constructing crosslinking density gradient across the thickness of the film. By integration of PULCN with near-infrared light-responsive polydopamine, local and sequential light control is achieved. This study may provide a new route for the fabrication of programmable and mechanically robust light-driven soft actuator.