Fabrication of cobalt-zinc bimetallic oxides@polypyrrole composites for high-performance electromagnetic wave absorption

In here, cobalt-zinc bimetallic oxides@polypyrrole (PPy) composites with core–shell structure are prepared, and the prepared Co3O4/ZnCo2O4@PPy (CZCP) has a wide absorption of 5.58 GHz, while ZnCo2O4/ZnO@PPy (ZCZP) has a strong reflection loss of −71.2 dB. [Display omitted] •By changing the ratio of Co2+ and Zn2+ of the MOF precursors, the various cobalt-zinc bimetallic oxides are fabricated.•Cobalt-zinc bimetallic oxides@polypyrrole (PPy) composites with core–shell structure are prepared through in situ polymerization method.•When the loading is 50 wt%, the EAB of Co3O4/ZnCo2O4@PPy is 5.58 GHz (12.42–18 GHz) at 1.53 mm, and the RLmin of ZnCo2O4/ZnO@PPy is −71.2 dB at 13.04 GHz and 1.84 mm. Composite materials that combine magnetic and dielectric losses offer a potential solution to enhance impedance match and significantly improve microwave absorption. In this study, Co3O4/ZnCo2O4 and ZnCo2O4/ZnO with varying metal oxide compositions are successfully synthesized, which are achieved by modifying the ratios of Co2+ and Zn2+ ions in the CoZn bimetallic metal–organic framework (MOF) precursor, followed by a high-temperature oxidative calcination process. Subsequently, a layer of polypyrrole (PPy) is coated onto the composite surfaces, resulting in the formation of core–shell structures known as Co3O4/ZnCo2O4@PPy (CZCP) and ZnCo2O4/ZnO@PPy (ZCZP) composites. The proposed method allows for rapid adjustments to the metal oxide composition within the inner shell, enabling the creation of composites with varying degrees of magnetic losses. The inclusion of PPy in the outer shell serves to enhance the bonding strength of the entire composite structure while contributing to conductive and dielectric losses. In specific experimental conditions, when the loading is set at 50 wt%, the CZCP composite exhibits an effective absorption bandwidth (EAB) of 5.58 GHz (12.42 GHz-18 GHz) at a thickness of 1.53 mm. Meanwhile, the ZCZP composite demonstrates an impressive minimum reflection loss (RLmin) of −71.2 dB at 13.04 GHz, with a thickness of 1.84 mm. This study offers a synthesis strategy for designing absorbent composites that possess light weight and excellent absorptive properties, thereby contributing to the advancement of electromagnetic wave absorbing materials.