One-step carbonization preparation of peanut shell porous carbon and its excellent microwave-absorbing property

Biomass-derived porous carbon is expected to become a lightweight and efficient microwave-absorbing material. In this paper, peanut shell porous carbon (PSC) materials was successfully prepared by a one-step carbonization method using peanut shells (PS) as raw material and KOH as activator. The prepared PSC samples had excellent microwave absorption performance. The effects of the proportion of activator (KOH), carbonization temperature and carbonization time on the micromorphology, electromagnetic parameters and microwave absorption properties of PSC were studied. In addition, relevant analyses were conducted on the graphitization degree, surface chemical composition and crystallinity of PSC samples. Results demonstrated that when the mass ratio of activator/PS was 0.75:1, the carbonization temperature was 700 °C, and the carbonization time was 2 h, the prepared PSC samples showed a low graphitization degree and had relatively abundant defect sites. The total pore volume was 0.6248 cm³/g, and the specific surface area was 1414.739 m²/g, presenting the porous morphology. For the PSC sample, at a thickness of 1.5 mm, the effective absorption bandwidth (EAB) for electromagnetic waves was 4 GHz, ranging from 13.76 GHz to 17.76 GHz, and the minimum reflection loss value reached -43.27 dB. The prepared PSC samples possessed abundant pore structures. The microporous structures increased the specific surface area and added energy dissipation sites, thereby enhancing the dielectric loss capacity of the materials and achieving efficient conversion of electromagnetic energy into thermal energy. The prepared PSC materials exhibited characteristics such as low density, small absorption thickness, and strong microwave absorption performance, which provided a basis for the development of lightweight and high-efficiency microwave absorption materials.