N-doped carbon matrix supported Fe3Ni6S8 hierarchical architecture with excellent sodium storage capability and electrocatalytic properties

Bimetallic sulfide Fe5Ni4S8 nanoparticles modified N/S co-doped carbon nanofibers as anode materials for high-performance sodium-ion batteries

Transition metal sulfides (TMSs) have garnered significant attention owing to high theoretical capacities, favorable environmental compatibility, abundant natural resources, and suitable discharge/charge voltage platform in the field of anode materials for sodium-ion batteries (SIBs). However, the sluggish reaction rates and significant volume alteration during the process of sodiation/desodiation restrict the practical application of TMSs for SIBs. Herein, a novel bimetallic sulfide Fe5Ni4S8 nanoparticles modified nitrogen/sulfur co-doped carbon nanofibers (NSCFs) composite is successfully synthesized using a straightforward electrostatic spinning and sulfurization treatment. As an anode material for SIBs, Fe5Ni4S8/NSCFs exhibits a high reversible specific capacity of 686.34 mAh g-1 at 0.1 A/g and a capacity of 607.26 mAh g-1 after 120 cycles at 1.0 A/g with a capacity retention rate of 96.9 %. Even at 10.0 A/g, it still maintains a capacity of 481.14 mAh g-1 after 800 cycles, indicating an excellent electrochemical energy storage performance. Density functional theory calculations demonstrate that the Fe5Ni4S8 exhibits enhanced binding with NSCFs, promoted electron transfers, improved Na+ adsorption ability, and decreased Na+ diffusion barrier energy compared to those of monometallic sulfide FeS. Additionally, the three-dimensional network skeleton of NSCFs can effectively enhance the electrical conductivity and relieve the volume change during the discharge and charge process. The innovative multicomponent design and nanostructural configuration provide a promising strategy to develop high-performance anode materials based on bimetallic sulfide for SIBs.

Mechanochemical one-pot synthesis of heterostructured pentlandite-carbon composites for the hydrogen evolution reaction

We have utilized carbon sources as milling additives to enable a direct mechanochemical one-pot synthesis of Fe3Co3Ni3S8/carbon (Pn/C) materials using elemental reaction mixtures. The obtained Pn/C materials are thoroughly characterized and their carbon content could be adjusted up to 50 wt%. In addition to carbon black (CB) as an additive, Pn/C materials were produced using graphite, reduced graphene oxide (rGO), and carbon nanotubes (CNTs), which allows the overall physicochemical properties of materials for energy storage applications to be adjusted. By employing the Pn/C materials as electrocatalysts for the HER in a zero-gap proton exchange membrane (PEM) electrolyzer, we were able to reach a current density of 1 A cm-2 at a cell potential as low as 2.12 V using Pn, which was synthesized with 25 wt% CB. Furthermore, electrolysis at an applied current density of 1 A cm-2 for 100 h displays a stable performance, thus providing a sustainable synthesis procedure for potential future energy storage applications. Herein, we show that catalyst supports play an important role in the overall performance.

Interfacial Electronic Rearrangement and Synergistic Catalysis for Alkaline Water Splitting in Carbon-Encapsulated Ni (111)/Ni3C (113) Heterostructures

The realization of efficient water electrolysis is still blocked by the requirement for a high and stable driving potential above thermodynamic requirements. An Ni-based electrocatalyst, is a promising alternative for noble-metal-free electrocatalysts but tuning its surface electronic structure and exposing more active sites are the critical challenges to improving its intrinsic catalytic activity. Here, we tackle the challenge by tuning surface electronic structures synergistically with interfacial chemistry and crystal facet engineering, successfully designing and synthesizing the carbon-encapsulated Ni (111)/Ni3C (113) heterojunction electrocatalyst, demonstrating superior hydrogen evolution reaction (HER) activities, good stabilities with a small overpotential of −29 mV at 10 mA/cm2, and a low Tafel slope of 59.96 mV/dec in alkaline surroundings, approximating a commercial Pt/C catalyst and outperforming other reported Ni-based catalysts. The heterostructure electrocatalyst operates at 1.55 V and 1.26 V to reach 10 and 1 mA cm−2 in two-electrode measurements for overall alkaline water splitting, corresponding to 79% and 98% electricity-to-fuel conversion efficiency with respect to the lower heating value of hydrogen.

Sustainable and rapid preparation of nanosized Fe/Ni-pentlandite particles by mechanochemistry

In recent years, metal-rich sulfides of the pentlandite type (M9S8) have attracted considerable attention for energy storage applications. However, common synthetic routes towards pentlandites either involve energy intensive high temperature procedures or solvothermal methods with specialized precursors and non-sustainable organic solvents. Herein, we demonstrate that ball milling is a simple and efficient method to synthesize nanosized bimetallic pentlandite particles (Fe4.5Ni4.5S8, Pn) with an average size of ca. 250 nm in a single synthetic step from elemental- or sulfidic mixtures. We herein highlight the effects of the milling ball quantity, precursor types and milling time on the product quality. Along this line, Raman spectroscopy as well as temperature/pressure monitoring during the milling processes provide valuable insights into mechanistic differences between the mechanochemical Pn-formation. By employing the obtained Pn-nanosized particles as cathodic electrocatalysts for water splitting in a zero-gap PEM electrolyzer we provide a comprehensive path for a potential sustainable future process involving non-noble metal catalysts.