CoS2/N,S co-doped mesoporous carbon with 3D micro-nano crosslinked structure as efficient bifunctional oxygen electrocatalysts for zinc-air batteries

Cascade Selenization Regulated the Electronic Structure and Interface Effect of Transition Metal Sulfides for Enhanced Sodium Storage

The utilization of cobalt-based sulfides is constrained by their inherently low conductivity and slow sodium ion diffusion kinetics. Modifying the electronic configuration and constructing heterostructures are promising strategies to enhance intrinsic conductivity and expedite the sodium ion diffusion process. In this study, heterogeneous nanoparticles of Se-substituted CoS2/CoSe2, embedded within heteroatom-modified carbon nanosheet, were synthesized using metal molten salt-assisted dimensionality reduction alongside concurrent sulfurization and selenization techniques. The incorporation of Se into CoS2 markedly enhances its intrinsic conductivity, thereby significantly improving its rate performance. The elongated Co-S bonds and the formation of CoSe2 species contribute to the acceleration of dynamics and facilitate the construction of the CoS2/CoSe2 heterointerface. In situ Raman spectroscopy, in conjunction with theoretical calculations, has elucidated the sodium storage mechanism of the Se-CoS2/CoSe2 and the underlying factors contributing to its enhanced performance. The synergistic effects of interface engineering and electronic structure engineering, have resulted in the optimized Se-CoS2/CoSe2 demonstrating exceptional rate performance, achieving 442 mAh g-1 at 10 A g-1, and a prolonged cycle lifespan, maintaining 409.3 mAh g-1 at 5 A g-1 over 2100 cycles and 262.5 mAh g-1 after 7000 cycles at 10 A g-1. This study presents a viable strategy for integrating electronic structure engineering with interface engineering.

Fe/Fe3C particles encapsulated in hollow carbon nanoboxes for high performance zinc-air batteries

Zinc-air batteries are recognized for their environmental friendliness and high energy density; however, the slow kinetics of the oxygen reduction reaction (ORR) at the air electrode hinder their commercial viability. The research focuses on synthesizing cubic hollow carbon structures derived from Metal-Organic Frameworks (MOFs), which enhance catalytic performance through improved conductivity and mass transfer. The resulting Fe/Fe3C/HCNB catalyst demonstrates a half-wave potential of 0.826 V for ORR and achieves a peak power density of 274 mW cm-2 in zinc-air batteries, surpassing commercial Pt/C catalysts. Electrochemical impedance spectroscopy reveals that the hollow structure enhances hydrophilicity and reduces solution resistance, facilitating greater active site engagement in electrochemical reactions. The study concludes that the unique structural features of Fe/Fe3C/HCNB significantly improve discharge performance and stability, positioning it as a promising alternative for zinc-air battery applications.

Low-temperature molten salt synthesis and catalytic mechanism of CoS2/NC as an advanced bifunctional electrocatalyst

The development of productive and sustainable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) plays an important role in the commercial evolution of metal-air batteries. In this paper, a low-temperature molten salt template method was adopted to synthesize the composite of CoS₂ and nitrogen-doped carbon (CoS₂/NC) without the protection of inert gas. The structural characterization studies show that the specific surface area (SSA) and crystal growth kinetics are increased and effectively improved, respectively, by the composite of CoS₂ and NC. The as-synthesized CoS₂/NC composite demonstrates outstanding bifunctional catalytic activity in alkaline electrolytes and exhibits a half-wave potential (E_1/2) of 0.854 V (vs. RHE) and an overpotential of only 220 mV for the OER at a current density of 10 mA cm^-2 (η₁₀). Simultaneously, CoS₂/NC also exhibits excellent electrochemical stability. Additionally, density functional theory (DFT) calculations have manifested that the synergistic effect of CoS₂ and NC results in a remarkable enhancement in the bifunctional catalytic performance of the composite materials. This study offers a new pathway and theoretical guidance for the fabrication of efficient bifunctional electrocatalysts.