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The Li–CO2 battery often suffers from high overpotential and limited capacity due to the challenges associated with the adsorption of Li+ and CO2 and the decomposition of Li2CO3. Herein, hexagonal rich-stepped NiSe crystals are in situ achieved on a three-dimensional (3D) free-standing porous Ni skeleton with double continuous channel architecture (namely p-Ni@NiSe-50) through an in situ selenization process. Structural characterization and theoretical calculation are applied to demonstrate the synergistic effects of marco/microstructural design and electronic band structure regulation. As a result, the adsorption/desorption of Li+ and CO2 and the formation/decomposition of Li2CO3 are effectively promoted, simultaneously, enabling an enhanced capacity and reversibility of p-Ni@NiSe-50 as the cathode of Li–CO2 battery. An ultra-low overpotential of 0.46 V and a remarkably high energy efficiency of 83.8% (20 μA cm−2) are achieved, along with a high full discharge specific capacity of 8844 μAh cm−2. Excellent long-term cycling stability (cycles up to 1000 h at a voltage gap of 1.14 V) of p-Ni@NiSe-50 is also obtained. The results of this work would provide a new insight and strategy to develop high-performance alkali metal-air batteries. Multi-scale synergistic effect of combining the cathode macroscopic structure design and the microscopic band structure design of NiSe was demonstrated to promote the adsorption of Li+ and CO2, as well as the decomposition of Li2CO3, so as to achieve ultra-low voltage gap and high capacity of Li-CO2 batteries. [ABSTRACT FROM AUTHOR]

The co-segregation of Cu and Mg solutes at grain boundaries (GBs) in Al alloys is widely observed in experiments, but this segregation pattern is much less understood. Herein, the Cu, Mg co-segregation behaviors and their effects on Al Σ5 (210) GB properties were systematically studied via first-principles calculations. The segregation order of Cu and Mg atoms was firstly determined wherein the segregation tendency of Cu is comparatively stronger than Mg. Calculations demonstrate that Cu and Mg atoms exhibit attractive interaction, which would promote synergistic co-segregation of both dopants at the GB. It is revealed that Cu, Mg co-segregation not only improves GB thermodynamic stability, but also enhances the GB fracture strength. Detailed analysis of charge density, bonding characteristics, etc., suggests that the newly formed Al–Cu bonds upon Cu segregation are the primary contribution to the increased GB cohesion. The further Mg doping at the Al GB with Cu segregation results in charge depletion and meanwhile decreases Al–Cu bonding length, the net results of which increase GB cohesion, suggesting a synergistically enhanced GB strength with Mg and Cu co-segregation. This work is supposed to provide fundamental insights into the effect of Cu, Mg co-segregation on the strength of Al GBs. [ABSTRACT FROM AUTHOR]

The marked Mg segregation at grain boundaries (GBs) in nanocrystalline Al alloys usually contributes additional GB segregation strengthening. To gain a further understanding of this phenomenon, molecular dynamics simulations were conducted to reveal the Mg segregation behavior at Al Σ9 (221)[ 1 1 ¯ 0 ] symmetric tilt grain boundary (STGB) and its effects on the GB stability and strength. Results reveal that Mg dopants have a large driving force to segregate at Al GBs. Such Mg segregation not only enhances the strength of Σ9 (221) STGB but also improves GB stability. It is found that the Mg segregation turns to enlarge and narrow the strain intervals of stable and thickening stages of Σ9 (221) STGB during tensile test, indicative of the Mg-induced stabilizing effect on the GB structural integrity. Calculations further elucidate that the segregated Mg dopants increase the critical stress for dislocation nucleation, which accounts for the remarkably increased tensile strength of Σ9 (221) STGB with Mg segregation. Such retarded dislocation nucleation is ascribed to the decrement in boundary free volume by Mg segregation. This work will provide important atomic-scale insights into the extra GB strengthening in Al alloys deriving from Mg segregation. [ABSTRACT FROM AUTHOR]

Performance of a mechanical buffer can be significantly improved by strengthening the materials and optimizing its structure. Manufacturing of high-strength and light-weight foam-filled tubes (FFTs) has been proved to be an ingenious strategy. In this work, the in situ grown carbon nanotubes (CNTs) were used to reinforce aluminum (Al) foams. The FFTs were prepared by inserting CNT/Al composite foams (CFs) into 6061 Al alloy empty tubes (ETs). The crushing behavior and energy absorption property of the as-prepared CNT/Al FFTs (C-FFTs) were evaluated using uniaxial compressive tests. The results show that the adopted CFs can effectively interact with outside tubes in C-FFTs. The C-FFTs significantly improve the compressive performance and energy absorption property, but only slightly increase the structure weight compared to single ETs. The plateau stress and energy absorption capacity of C-FFTs are nearly 3.5 and 3.7 times higher than those of ETs, respectively. This phenomenon is ascribed to the stable support of CFs and the excellent load transfer ability of CNTs. [ABSTRACT FROM AUTHOR]

A hybrid of graphene nanoribbons (GNRs) interlacing hollow NiCoO (G-HNCO) nanocages in a size range of 300~500 nm with rough surface is synthesized by a chemical etching CuO templates and followed by GNR interlacing process. The G-HNCO showed high electrochemical performance of oxygen evolution reaction (OER), which exhibited small onset potential of 1.50 V and achieved current densities of 10 mA cm at potentials of 1.62 V. Also, the hybrid delivered high capacitance of 937.8 F g at 1 A g in supercapacitor (SC) tests as well as stable cycling performance in both OER and SC measurements. The approach to synthesize the hybrid is simple and scalable for other graphene nanoribbon-based electrocatalysts. [ABSTRACT FROM AUTHOR]