Co/N-C nanotubes with increased coupling sites by space-confined pyrolysis for high electrocatalytic activity

Searching low cost and non-precious metal catalysts for high-performance oxygen reduction reaction is highly desired. Herein, Co nanoparticles embedded in nitrogen-doped carbon(Co/N—C) nanotubes with internal void space are successfully synthesized by space-confined pyrolysis, which effectively improve the cobalt loading content and restrict the encapsulated particles down to nanometer. Different from the typical conformal carbon encapsulation, the resulting Co/N—C nanotubes possess more cobalt nanoparticles embedded in the nanotubes, which can provide more coupling sites and active sites in the oxygen reduction reaction(ORR). Moreover, the one-dimensional and porous structure provides a high surface area and a fast electron transfer pathway for the ORR. And the Co/N—C electrode presents excellent electrocatalytic ORR activity in terms of low onset potential(30 mV lower than that of Pt/C), small Tafel slop(45.5 mV dec^(-1)) and good durability(88.5% retention after 10,000 s).

Oxyvanite V3O5:A new intercalation-type anode for lithium-ion battery

In the present study,V3O5 microcrystals that synthesized via vacuum calcination are employed as anodes for lithium-ion batteries(LIBs)for the first time.Despite the widely observed sluggish reaction kinetics and poor cycling stability in most microsized transition metal oxides,the V3O5 microcrystals exhibit excellent rate capability(specific capacities of 144 and 125 mAh g^−1 are achieved at extremely high current densities of 20 and 50 A g^−1,respectively)and long-term cycling performance(specific capacity of 117 mAh g^−1 is sustained over 2000 cycles at 50 A g^−1).It is ascribed to the three-dimensional open-framework structure of the V3O5 microcrystals as a major factor in dictating the fast reaction kinetics(lithium diffusion coefficient:~10−9 cm^2 s^−1).In addition,significant insight into the reaction mechanism of the V3O5 microcrystals in concomitant its phase evolution are obtained from ex-situ XRD study,revealing that the V3O5 microcrystals undergo intercalation reaction with insignificant structural change in response to lithiation/delithiation.