Morphology, size, and defect engineering in CeOHCO3 hierarchical structures for ultra-wide band microwave absorption

Abstract

The growing electromagnetic interference problem triggers higher requirements for exploration into new electromagnetic wave (EMW) absorbers and new absorption mechanisms. Herein, we developed a simple and rapid microwave-assisted hydrothermal approach for the controllable synthesis of a butterfly-shaped Ce(OH)CO₃ hierarchical structure as an efficient EMW absorber for the first time. Kinetic factors, including the CO(NH₂)₂/Ce³⁺ molar ratio (β), reaction temperature (T), and reaction time, can be expediently utilized to tune the size, morphology, and defects of the products, which is helpful for tailoring the EMW absorption capability. The cooperation of selective adsorption and minimum surface free energy results in the evolution of the morphology. The appropriate defects, oxygen vacancies, and surface functional groups along with hierarchical structure can synergistically benefit the superior EMW absorbing capacity. Strong damping and perfect impedance matching can be achieved by tuning the balance between conductivity loss and polarization loss. Excellent comprehensive properties are reached at T = 140 °C and β = 2.5 : 1 with a maximal absorption bandwidth of 9.52 GHz, which is significantly broader than those of the previously reported cerium-based compounds/composites. Our current work not only sheds light on the precisely controllable synthesis of hierarchical structures but also opens up a novel methodology for designing new efficient EMW absorbers.