RESUMO
Highly oriented Co-MOF nanoneedle arrays arein situconstructed on Co foam (Co-MOF@Co) by using a one-pot solvothermal strategy. As-prepared Co-MOF@Co can be directly served as a binder-free electrode for supercapacitor, which exhibits wonderful electrochemical performances, i.e. high specific capacitance (12783.0 mF cm-2or 1164.2 F g-1), exceptional cycling stability (90.5% retention over 10 000 cycles at 250 mA cm-2) with a loading of 10.98 mg cm-2. Meanwhile, an asymmetric supercapacitor of AC//Co-MOF@Co delivers a high ratability (87% retention upon ten-fold current density) and high energy density of 43.4 W h kg-1at the power density of 145.1 W kg-1.
RESUMO
One of the most important challenges for heterogeneous wireless sensor networks (HWSNs) is adequate network coverage and connectivity. Aiming at this problem, this paper proposes an improved wild horse optimizer algorithm (IWHO). Firstly, the population's variety is increased by using the SPM chaotic mapping at initialization; secondly, the WHO and Golden Sine Algorithm (Golden-SA) are hybridized to improve the WHO's accuracy and arrive at faster convergence; Thirdly, the IWHO can escape from a local optimum and broaden the search space by using opposition-based learning and the Cauchy variation strategy. The results indicate that the IWHO has the best capacity for optimization by contrasting the simulation tests with seven algorithms on 23 test functions. Finally, three sets of coverage optimization experiments in different simulated environments are designed to test the effectiveness of this algorithm. The validation results demonstrate that the IWHO can achieve better and more effective sensor connectivity and coverage ratio compared to that of several algorithms. After optimization, the HWSN's coverage and connectivity ratio attained 98.51% and 20.04%, and after adding obstacles, 97.79% and 17.44%, respectively.
RESUMO
A functioned PP was chosen as a separator to suppress the shuttling effect of soluble polysulfide in lithium-sulfur batteries (LSBs). Nanocubic cobalt phosphide/carbon (CoP/C) was modified on PP membrane through a simple vacuum filtration method. This CoP/C-modified PP separator not only efficiently captures polysulfides through strong chemical affinity but also facilitates the conversion of the soluble intermediates due to the fast transfer at the interface. In consequence, the cell with a CoP/C-modified separator exhibits a low-capacity decay of only 0.08% per cycle over 500 cycles at 1 C with an initial capacity of 938 mAh g-1 and a superior rate performance of 594 mAh g-1 at 4 C. Even with a high loading of 3.2 mg cm-2, the cell still exhibits an excellent reversible capacity of 601.3 mAh g-1 after 100 cycles at 0.5 C. This work provides a new strategy to effectively restrict the polysulfide shuttling.
RESUMO
Perovskites have become important OER electrocatalysts. Herein, as-prepared La0.8Sr0.2Co0.8Fe0.2O3-δ (LSCF-0) is chosen as a sample to exhibit the superimposed effect of surface reconstruction accompanied by reduction of Co3+ to Co2+ on the further improvement of its activity and stability. As-synthesized LSCF-0 perovskite is chemically treated by simply immersing in an aqueous solution of NaBH4 for 1.0 h at room temperature. The optimized LSCF (LSCF-2) owns an amorphous layer consisting of nanosized particles of â¼20 nm (vs smooth bulk crystalline surface for untreated LSCF), which exhibits superior OER performance to LSCF-0. LSCF-2 has an overpotential of 248 mV (10 mA cm-2) and a Tafel slope of 51 mV dec-1 (vs 355 mV and 76 mV dec-1 for LSCF-0 and 381 mV and 91 mV dec-1 for LCO) and an excellent cycle stability for 20 h running. This work supplies a new strategy to enhance OER performance through surface reconstruction of as-prepared perovskites.