Tuning Oxygen Vacancy Concentration in Defect-Engineered Black TiO ₂ Nanomaterials for Synergistically Enhanced Microwave Absorption Performance

With the rapid advancement of 5G communication and artificial intelligence technologies, the ubiquitous deployment of electronic apparatuses has raised pressing issues relating to signal interference and electromagnetic pollution, driving intensive research into microwave-absorbing materials. This article proposed a defect engineering-driven strategy to endow nanostructured TiO2 with excellent microwave absorption performance through the synergistic optimization of oxygen vacancies and core–shell nanostructure design. By precisely controlling the hydrogenation temperature (300–450 °C) and TiO2/NaBH4 ratio (1–4), we achieved tunable microwave absorption performance. Under optimal conditions, the nanomaterial exhibited a RLmin of −32.95 dB and an effective absorption bandwidth of 2.794 GHz, showing great promise for electromagnetic interference shielding in next-generation communication devices and radar systems. The concentration of oxygen vacancies was the core factor affecting the absorption performance. Incorporating oxygen vacancies not only enhanced defect-induced polarization and interface polarization effects but also strengthened conductivity loss by increasing carrier concentration. The collaborative interplay of these three mechanisms endows the nanostructured material with a superior microwave attenuation capability. The findings provide theoretical and practical guidance for developing lightweight, broadband, and highly efficient black TiO2-derived microwave absorbers. Our findings offer practical guidance for developing advanced microwave absorbers for next-generation aerospace radar and communication systems.