Tailored heterostructured Ni_(3)N-NiO nano-frameworks for boosting electrocatalytic oxygen evolution via surface-modulated plasma strategy

The facile reconfiguration of phases plays a pivotal role in enhancing the electrocatalytic production of H2 through heterostructure formation.While chemical methods have been explored extensively for this purpose,plasma-based techniques offer a promising avenue for achieving heterostructured nano-frameworks.However,the conventional plasma approach introduces complexities,leading to a multi-step fabrication process and challenges in precisely controlling partial surface structure modulation due to the intricate interaction environment.In our pursuit of heterostructures with optimized oxygen evolution reaction(OER)behavior,we have designed a facile auxiliary insulator-confined plasma system to directly attain a Ni_(3)N-NiO heterostructure(hNiNO).By meticulously controlling the surface heating process during plasma processing,such approach allows for the streamlined fabrication of hNiNO nano-frameworks.The resulting nano-framework exhibits outstanding catalytic performance,as evidenced by its overpotential of 320 mV at a current density of 10 mA·cm^(-2),in an alkaline environment.This stands in stark contrast to the performance of NiO-covered Ni_(3)N fabricated using the conventional plasma method(sNiNO).Operando plasma diagnostics,coupled with numerical simulations,further substantiates the influence of surface heating due to auxiliary insulator confinement of the substrate on typical plasma parameters and the formation of the Ni_(3)N-NiO nanostructure,highlighting the pivotal role of controlled surface temperature in creating a high-performance heterostructured electrocatalyst.

Tuning magnetic properties, thermal stability and microstructure of NdFeB magnets with diffusing Pr-Zn films

Grain boundary diffusion process(GBDP)serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets.Herein,non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported.The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated.Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m^-1 to 1317.14 kA m^-1 without any remanence reduction.Notably,the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio.The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment.The well-optimized rare earth-rich(RE-rich)grain boundary phases and high effective anisotropy field of(Nd,RE)2 Fe14 B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of Nd FeB permanent magnets via GBDP treatment.

Enhancing bifunctionality of CoN nanowires by Mn doping for long-lasting Zn-air batteries

Tailoring the nanostructure and composition of transition metal nitrides is highly important for their use as potent low-cost electrocatalysts. Cobalt nitride(CoN) exhibits strong catalytic activity for oxygen evolution reaction(OER). However, its poor catalytic efficiency for oxygen reduction reaction(ORR) hinders its application in rechargeable zinc-air batteries(ZABs) as the air cathode. In this work, we deploy the effective strategy of Mn doping to improve both OER and ORR activity of CoN nanowires as the cathode material for ZAB. Theoretical calculation predicts that moderate Mn doping in cobalt nitride results in a downshift of the d-band center and reduces the adsorption energy of reaction intermediates. With ~10 at% Mn dopants, stronger catalysis activities for both OER and ORR are achieved compared to pure CoN nanowires. Subsequently, both aqueous and flexible quasi-solid-state ZABs are constructed using the Mn-doped CoN nanowires array as additive-free air cathode. Both types of devices present large open circuit potential, high power density and long-cycle stability. This work pushes forward the progress in developing cost-effective ZABs.