RESUMEN
The enhancement of the structural stability of conversion-based metal sulfides at high current densities remains a major challenge in realizing the practical application of sodium-ion batteries (SIBs). The instability of metal sulfides is caused by the large volume variation and sluggish reaction kinetics upon sodiation/desodiation. To overcome this, herein, a heterostructured nanocube anode composed of CuS/FeS2 embedded in nitrogen-doped carbon (CuS/FeS2 @NC) is synthesized. Size- and shape-controlled porous carbon nanocubes containing metallic nanoparticles are synthesized by the two-step pyrolysis of a bimetallic Prussian blue analog (PBA) precursor. The simple sulfurization-induced formation of highly conductive CuS along with FeS2 facilitates sodium-ion diffusion and enhances the redox reversibility upon cycling. The mesoporous carbon structure provides excellent electrolyte impregnation, efficient charge transport pathways, and good volume expansion buffering. The CuS/FeS2 @NC nanocube anode exhibits excellent sodium storage characteristics including high desodiation capacity (608 mAh g-1 at 0.2 A g-1 ), remarkable long-term cycle life (99.1% capacity retention after 300 cycles at 5 A g-1 ), and good rate capability up to 5 A g-1 . The simple, facile synthetic route combined with the rational design of bimetallic PBA nanostructures can be widely utilized in the development of conversion-based metal sulfides and other high-capacity anode materials for high-performance SIBs.
RESUMEN
Molybedenum disulfide (MoS2) is regarded as a promising anode material for next-generation sodium-ion batteries (SIBs) owing to its high theoretical capacity. However, its low conductivity, large volume changes, and undesirable phase transformation hinder its practical applications. In this study, we synthesize a hierarchically designed core-shell heterostructure based on nitrogen-doped MoS2/C and silicon oxycarbide (SiOC) (N-MoS2/C@SiOC) via the facile pyrolysis of a suspension of an N-MoS2/polyfurfural precursor in silicone oil. The in situ nitrogen doping in a two-dimensional MoS2 structure with carbon incorporation leads to the enlargement of the interlayer spacing and enhancement of the electronic conductivity and mechanical stability, which allows the facile, highly reversible insertion and extraction of sodium ions upon cycling. Further, the nanoscale SiOC shell with surface capacitive reactivity provides a conductive pathway, preventing unfavorable side reactions at the electrode/electrolyte interface and acting as a structure-reinforcing buffer against severe volume expansion issues. As a result, the N-MoS2/C@SiOC composite exhibits high reversible capacity (540.7 mAh g-1), high-capacity retention (>100% after 200 cycles), and excellent rate capability up to 10 A g-1. The simple hierarchical core-shell design strategy developed in this study allows for the fabrication of high-performance metal sulfide anodes as well as other high-capacity anode materials for energy storage applications.
RESUMEN
Mesoporous nickel-iron-alumina xerogel ((40-x)Ni(x)FeAX) nano-catalysts with different iron content (x = 0, 2.5, 5, 7.5, and 10) were prepared by a single-step sol-gel method for use in the methane production from carbon monoxide and hydrogen. The effect of iron content on the catalytic performance of (40-x)Ni(x)FeAX catalysts was investigated. In the methanation reaction, yield for CH4 decreased in the order of 35Ni5FeAX > 32.5Ni7.5FeAX > 30Ni10FeAX > 37.5Ni2.5FeAX > 40Ni0FeAX. This indicated that optimal iron content of mesoporous nickel-iron-alumina xerogel nano-catalyst was required for maximum production of CH4 in the methanation reaction. Experimental results revealed that optimal CO dissociation energy and large H2 adsorption ability of the catalyst were favorable for methane production. Among the catalysts tested, 35Ni5FeAX catalyst, which retained the most optimal CO dissociation energy and the largest H2 adsorption ability, exhibited the best catalytic performance in terms of conversion of CO and yield for CH4 in the methanation reaction. CO dissociation energy and H2 adsorption ability of the catalyst played a key role in determining the catalytic performance of (40-x)Ni(x)FeAX in the methanation reaction.
