Defect-engineered hollow black TiO2 for enhanced microwave absorption via interface polarization

Abstract

The exponential expansion of electronic devices has significantly augmented concerns regarding electromagnetic interference. This has led to a growing emphasis on developing materials with outstanding microwave-absorbing capabilities in materials science. Black titanium dioxide (TiO₂) has come to the fore as a material of exceptional promise, captivating researchers’ attention owing to its notable electrical conductivity and its electronically tunable structure. In this research, hollow black TiO₂ featuring abundant heterostructures was successfully prepared using the template method, exhibiting excellent microwave attenuation properties. This material demonstrated a remarkable maximum reflection loss reaching −62.1 dB and displayed a broad effective bandwidth of 4.24 GHz. The improvement in microwave absorption can be primarily ascribed to the incorporation of defects and hollow structures, such as oxygen vacancies. Defects endow black TiO₂ with a unique heterostructure, featuring disordered shell layers surrounding the crystal. This structure strengthens dipole and interface polarization effects, thereby improving microwave attenuation. Additionally, oxygen vacancy defects enhance the material’s conductivity, increasing conduction losses. Furthermore, the hollow structure further promotes the occurrence of numerous scattering and reflections of incident waves, thereby extending their transmission path. These results provide substantial and useful guidance for the engineering and construction of core–shell microwave absorbers primarily composed of black TiO₂.