In Situ Dual-Template Method of Synthesis of Inverse-Opal Co3O4@TiO2 with Wideband Microwave Absorption.

A unique porous TiO2 with Co3O4 nanoparticles anchored in (Co3O4@TiO2) is prepared by a dual-templating method for promoting electromagnetic microwave absorption (EMA). The as-prepared Co3O4@TiO2 possesses a three-dimensional (3D) ordered macroporous TiO2 skeleton and plenty of mesopores, as well as small Co3O4 nanoparticles that coexisted in the macropore walls of the TiO2 skeleton. The introduction of Co3O4 can increase the magnetic loss as well as suppress impedance mismatch, resulting in the regulation of the EMA performance. The synergetic effect of the TiO2 porous framework and Co3O4 nanoparticles with proper ratio promote microwave absorption performance. Therefore, Co3O4@TiO2-2 with 25 wt % Co3O4 nanoparticles content displays a strong and ultrawide effective absorption band (EAB) performance. The Co3O4@TiO2-2 presents a strong reflection loss of -53.9 dB at 2.95 mm. Moreover, it obtains a super broad EAB of ∼12.5 GHz at 5.0 mm. This dual-templating approach for a well-controlled porous structure could be a facial strategy for the development of high-performance electromagnetic wave absorbers.