Carbon Dots-Derived Gradient-Pore Multilayer Graphene Enabled Efficient Electromagnetic Wave Absorption.

Rational design and preparation of a low-cost electromagnetic wave absorber are highly desired but remain a significant challenge. In this experiment involving the dimensionality engineering of carbon materials, multilayer graphene with gradient pores from nanometer to micrometer sizes were prepared by annealing carbon dots and nanocobalt powder. The heterogeneous interface between the gradient-pore multilayer graphene and the cobalt anchoring synergistically enhances interfacial polarization, while the multireflection within the porous architecture, combined with the intrinsic magnetic loss of nanocobalt, endows the composites with remarkable dielectric and magnetic loss capabilities. This cooperative dielectric-magnetic loss mechanism significantly promotes electromagnetic wave dissipation and optimizes the impedance matching of the material. As a result, the obtained nanocobalt-anchored gradient-pore multilayer graphene exhibits an exceptional minimum reflection loss of -56.0 dB, with an effective absorption bandwidth of 3.0 GHz, and it also achieves a minimum reflection loss of -38.5 dB and a broad effective absorption bandwidth of 5.1 GHz. This work reveals a dimensionality transition from zero-dimensional carbon dots to two-dimensional graphitic architectures, accompanied by pores emerging during the high temperature reaction. The insights provide a feasible strategy for designing high performance electromagnetic wave absorbers, ensuring that they are highly promising material candidates for addressing electromagnetic pollution challenges.