PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.

NiS_(2)/FeS Heterostructured Nanoflowers for High-Performance Sodium Storage

Transition metal sulfides demonstrate attractive potential for sodium storage owing to their high theoretical specific capacity and high reserve.However,the low conductivity and volume expansion deteriorate their high-rate performance and cycling stability.In this work,we construct NiS_(2)/FeS heterostructure by growing Ni-based layered double hydroxide nanosheets on Fe-based Prussian Blue nanocrystals followed by gaseous sulfurization,giving rise to flower-like NiS_(2)/FeS nanoparticles.The as-prepared nanocomposite exhibits good rate performance of 156 mAh g^(−1) at 50 A g^(-1) and long cycle life of 606 mAh g^(−1) at 5 A g^(−1) after 1,000 cycles,which are superior to the heterostructure-free counterpart of NiS_(2) and FeS.Density functional theory calculation further verifies that the enhanced electrochemical performance of NiS_(2)/FeS is due to the existence of interface derived from the heterostructure.

In-situ construction of Li4Ti5O12/rutile TiO2 heterostructured nanorods for robust and high-power lithium storage

Li4Ti5O12 is considered as a safe and stable anode material for high-power lithium-ion batteries due to its“zero-strain”characteristic during the charge/discharge.However,the intrinsically low electronic conductivity leads to a deterioration in highrate performance,impeding its intensive application.Herein,the Li4Ti5O12/rutile TiO2(LTO/RT)heterostructured nanorods with tunable oxide phases have been in-situ fabricated by annealing the electrospun nanofiber precursor.By constructing such a heterostructured interface,the as-prepared sample delivers a high capacity of 160.3 mAh·g–1 at 1 C after 200 cycles,125.5 mAh·g–1 at 10 C after 500 cycles and a superior capacity retention of 90.3%after 1,000 cycles at 30 C,outperforming the heterostructure-free counterparts of pure LTO,RT and the commercial LTO product.Density Functional Theory calculation suggests a possible synergistic effect of the LTO/RT interface that would improve the electronic conductivity and Li-ion diffusion.

Highly Efficient Na+ Storage in Uniform Thorn Ball-Like α-MnSe/C Nanospheres

Because of its high theoretical capacity,MnSe has been identified as a promising candidate as the anode material for sodiumion batteries.However,its fast capacity deterioration due to the huge volume change during the intercalation/deintercalation of sodium ions severely hinders its practical application.Moreover,the sodium storage mechanism of MnSe is still under discussion and requires in-depth investigations.Herein,the unique thorn ball-likeα-MnSe/C nanospheres have been prepared using manganese-containing metal organic framework(Mn-MOF)as a precursor followed by in situ gas-phase selenization at an elevated temperature.When serving as the anode material for sodium-ion battery,the as-preparedα-MnSe/C exhibits enhanced sodium storage capabilities of 416 and 405 mAh g^(-1)at 0.2 and 0.5 A g^(-1)after 100 cycles,respectively.It also shows a superior capacity retention of 275 mA h g^(-1)at 10 A g^(-1)after 2000 cycles,and a rate performance of 279 mA h g^(-1)at 20 A g^(-1).Such sodium storage properties could be attributed to the unique structure offering a highly efficient Na+diffusion kinetics with a diffusion coefficient between 1×10^(-11) and 3×10^(-10) cm^(2) s-1.The density functional theory calculation indicates that the fast Na+diffusion mainly takes place on the(100)plane of MnSe along a V-shaped path because of a relatively low diffusion energy barrier of 0.15 eV.