Amorphous 3D pomegranate-like NiCoFe nanoassemblies derived by bi-component cyanogel reduction for outstanding oxygen evolution reaction

As a representative type of self-supported templates, cyano-bridged cyanogels provide ideal plateaus for synthesis of three-dimensional(3 D) nanostructures. Herein, 3 D pomegranate-like Fe-doped NiCo nanoassemblies(3 D PG-NiCoFe NAs) were synthesized via facile one-step bi-component cyanogel reduction with NaBH_4 as the reducing agent. Specifically, the influence of the incorporated Fe amount was carefully investigated by finely adjusting the feeding molar ratios of the Ni/Co/Fe atoms in the precursors.By virtue of the unique structure and enriched oxygen vacancies originated from well-modulated electronic structures, the 3 D PG-NiCoFe-211 NAs exhibited outstanding electrocatalytic performances for oxygen evolution reaction(OER) in alkaline solution, outperforming commercial RuO_2 catalyst. The current incorporation of foreign metal atom into host material provides some valuable insights into design and synthesis of metal-based nanocatalysts for constructing practical water splitting devices.

Strengthening absorption ability of Co-N-C as efficient bifunctional oxygen catalyst by modulating the d band center using MoC

Co-N-C is a promising oxygen electrochemical catalyst due to its high stability and good durability.However,due to the limited adsorption ability improvement for oxygen-containing intermediates,it usually exhibits inadequate catalytic activity with 2-electron pathway and high selectivity of hydrogen peroxide.Herein,the adsorption of Co-N-C to these intermediates is modulated by constructing heterostructures using transition metals and their derivatives based on d-band theory.The heterostructured nanobelts with MoC core and pomegranate-like carbon shell consisting of Co nanoparticles and N dopant(MoC/Co-N-C)are engineered to successfully modulate the d band center of active Co-N-C sites,resulting in a remarkably enhanced electrocatalysis performance.The optimally performing MoC/Co-N-C exhibits outstanding bi-catalytic activity and stability for the oxygen electrochemistry,featuring a high wave-half potential of 0.865 V for the oxygen reduction reaction(ORR)and low overpotential of 370 mV for the oxygen evolution reaction(OER)at 10 mA cm^(-2).The zinc air batteries with the MoC/Co-N-C catalyst demonstrate a large power density of 180 mW cm^(-2)and a long cycling lifespan(2000 cycles).The density functional theory calculations with Hubbard correction(DFT+U)reveal the electron transferring from Co to Mo atoms that effectively modulate the d band center of the active Co sites and achieve optimum adsorption ability with"single site double adsorption"mode.

Se-decorated SnO_(2)/rGO composite spheres and their sodium storage performances

SnO_(2) is considered a promising anode material for sodium-ion batteries due to its high theoretical capacity and low cost.However,the poor electrical conductivity and dramatic volume variation during cha rge/discharge cycling is a major limitation in its practical applicability.Here we propose a simple onepot spray pyrolysis process to construct unique pomegranate-like SnO_(2)/rGO/Se spheres.The ideal structural configuration of these architectures was effective in alleviating the large volume variation of SnO_(2),besides facilitating rapid electron transfer,allowing the devised anode to exhibit superior sodium sto rage performances in terms of capacity(506.7 mAh/g at 30 mA/g),cycle performance(397 mAh/g after100 cycles at 50 mA/g) and rate capability(188.9 mAh/g at an ultrahigh current density of 10 A/g).The experimental evidence confirms the practical workability of p-SnO_(2)/rGO/Se spheres in SIBs.