Defect-rich heterostructures in sulfide/carbon composites trigger strong polarization coupling, enhancing electromagnetic wave absorption

In the rapidly evolving landscape of technology, where innovation continually redefines boundaries, materials science stands as a driving force behind transformative advancements across diverse fields. A recent breakthrough from Northwestern Polytechnical University highlights this dynamic, presenting a remarkable advancement in electromagnetic wave (EMW) absorption materials. The findings, published in a prestigious journal, introduce a groundbreaking series of sulfide/carbon composites enriched with sulfur-vacancy-rich sulfides at their heterointerfaces. These materials were developed using an innovative one-pot carrageenan-assisted, cation-regulated synthesis strategy that not only simplifies fabrication but also significantly enhances EMW absorption performance.

Led by the visionary Professor Hongjing Wu, the research team sought to overcome traditional synthesis challenges—often hindered by complexity and energy-intensive processes—that limit scalability and practical application. Their pioneering method employs water-soluble ι-carrageenan as both a carbon matrix precursor and a sulfur source, seamlessly integrating these components in a single-step process.

The study’s success hinges on the strategic introduction of sulfur vacancies and the formation of diverse sulfides within the carbon matrix. By meticulously tuning specific cations—Co²⁺, Ni²⁺, or their synergistic combination—the team engineered heterointerfaces teeming with sulfur vacancies. These heterointerfaces disrupt lattice periodicity and modify charge carrier transport dynamics, enhancing electron accumulation and consumption capabilities while amplifying dielectric polarization loss.

Comprehensive characterization techniques validated the exceptional properties of the composites. X-ray diffraction (XRD) confirmed the presence of various sulfides, while X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) revealed sulfur vacancies and lattice defects. A vector network analyzer provided precise measurements of EMW parameters, showcasing the composites' absorption efficiency.

The results are remarkable. The optimized Co/Ni-CAs composites, enriched with sulfur-vacancy-rich sulfides, achieved a broad absorption bandwidth of 6.76 GHz at a remarkably thin layer of just 1.8 mm. This performance surpasses previously reported sulfides/carbon composites, making them highly attractive for both military and civilian applications.

The underlying mechanisms behind this exceptional performance were elucidated through theoretical analyses. The heterointerfaces generate a multitude of electric dipoles, driving interfacial polarization under alternating electric fields. This interfacial polarization is significantly enhanced in the Co/Ni-CAs due to their sulfur vacancies and precisely engineered heterointerfaces.

Sulfur vacancies also induce local asymmetry in the electronic structure, promoting defect-induced dipole polarization, which substantially boosts the composites' dissipation capabilities, as reflected in their high attenuation constant (α). Notably, the α values for Co-CAs, Ni-CAs, and Co/Ni-CAs far exceeded those of the control sample (CAs) lacking metal ions.

Moreover, theoretical calculations revealed that sulfur-vacancy-rich heterointerfaces accelerate charge migration and create a built-in electric field, further intensifying interfacial polarization. This self-driven charge redistribution at the heterointerfaces amplifies polarization coupling, enhancing the overall performance of the composites.

In addition to their superior EMW absorption properties, the composites demonstrated excellent stability and durability, maintaining consistent performance even under harsh conditions and prolonged use.

This study marks a significant milestone in the development of EMW absorption materials. By integrating sulfur vacancies and diverse sulfide heterointerfaces within a carbon matrix, the research team has produced composites with robust polarization coupling and unparalleled EMW absorption capabilities. These innovations are poised to revolutionize applications ranging from military stealth technology to advanced electronic devices and communication systems.