Defect Engineering of Mo Single-Atoms and Confinement of Mo Clusters in Porous Carbon Nanoflowers for Efficient Electromagnetic Wave Absorption.

Metal single-atom-based materials exhibit remarkable electromagnetic wave absorption capabilities; however, the role of local microstructures, particularly defect-induced symmetry-broken configurations, remains insufficiently understood. Herein, Mo single-atoms with a symmetry-broken Mo-N3 coordination environment are engineered within carbon nanoflowers to clarify the influence of the local microstructure of Mo species on dielectric behavior and electromagnetic wave absorption performance. For comparison, Mo-containing clusters and MoxOy nanoparticles are also introduced into the carbon nanoflowers. Theoretical calculations demonstrate that defect-containing Mo-N3 sites possess superior dielectric properties relative to conventional Mo-N4 configurations, owing to the asymmetric charge distribution induced by carbon defects in the first coordination shell. Experimental results reveal that the Mo-N3 configuration within carbon nanoflowers shows superior electromagnetic wave absorption performance with an effective absorption bandwidth of 5.31 GHz at a thickness of 2.0 mm. In addition, it is also found that Mo-containing clusters facilitate the reflection loss value, while symmetry-broken Mo-N3 sites can expand the effective absorption bandwidth at a thinner thickness. These results demonstrate that tailoring local environments of Mo single-atoms and construction of clusters are promising strategies for optimizing the electromagnetic wave absorption property of an absorber.