Lightweight epsilon-near-zero aerogel at radio frequency with water evaporation performance

Epsilon-near-zero (ENZ) materials, due to their unique physical properties, exhibit significant applications in the fields of perfect absorption, high-order harmonics, etc., and have achieved breakthroughs in performance when combined with a variety of electronic devices. Here, lightweight radio frequency ENZ aerogel is designed for the first time, via fabricating polyurethane/high-entropy alloy@carbon (PU/HEA@C) aerogel through entropy engineering strategy, which is an important step in the integration with radio frequency electronic devices. In addition, PU/Cu@C and PU/CoNiCu@C aerogels are also prepared, and their dielectric properties are investigated. With the increase of entropy, the plasma frequency of the aerogel gradually decreases, and the ENZ performance at 24 MHz is achieved in PU/HEA@C aerogel. It is proved by theoretical calculation that with the increase of entropy, the band structure of the alloy becomes flatter, so the non-parabolicity is enhanced, indicating that the effective electron mass is increased, thereby resulting in the reduced plasma frequency of PU/HEA@C aerogel to radio frequency. Moreover, PU/HEA@C aerogel shows excellent water evaporation performance of 3.21 kg·m⁻²·h⁻¹ under 1 sun irradiation, due to enhanced d-d interband transitions in HEA. This work provides new theoretical guidance for the realization of lightweight and multi-functional aerogels with ENZ performance.