Anion‐Doping‐Induced Vacancy Engineering of Cobalt Sulfoselenide for Boosting Electromagnetic Wave Absorption

Abstract Vacancy engineering is an attractive approach to modulate the electronic structure of transition metal chalcogens. However, illustrating how anion vacancy can be engineered to tailor their electromagnetic (EM) parameters and electromagnetic wave (EMW) absorption, based on clear vacancy concentrations and/or various anion vacancies rather than semiempirical rules, is currently lacking but significantly desired. An anion‐doping‐induced vacancy engineering is pioneered, where the selective oxidation process upgrades the transformation from Co‐based precursor to S‐doped CoSe 2 (System II) instead of Se‐doped CoS 2 (System I) in the subsequent sulfuration/selenization, which results in vacancy level improvement and coexistence of sulfur vacancies (V S ) and selenium vacancy ( V Se ). Thanks to the boosted dielectric polarization loss provided by the comparable coexistence of sulfur/selenium vacancies (V S /V Se = 0.52), S‐doped CoSe 2 harvests a broad bandwidth of 9.25 GHz (8.75–18.00 GHz) at 2.42 mm. This feature almost simultaneously achieves 100% coverage for X ‐, and Ku ‐bands, outperforming all reported metal sulfides/selenides until now. This work establishes a clear correlation between vacancy concentrations/various anion vacancies and EMW dissipation ability, offering valuable insights for designing advanced EMW absorbing materials.