GO-HNT framework-based hydrogels with efficient water evaporation-driven cooling and superior electromagnetic wave absorption†

Heat dissipation and electromagnetic wave absorption (EWA) are crucial for mitigating heat accumulation and electromagnetic interference issues in electronics. Conventionally, incorporation of specific fillers to polymer substrates is widely adopted to address these issues, although it is often challenging to simultaneously realize high thermal conductivity and effective EWA performance via this approach. In this work, graphene oxide/halloysite nanotube (GH) frameworks were incorporated into hydrogels. Benefiting from the unique three-dimensional hierarchical network of GH frameworks, impedance matching was optimized, and thus, the optimized hydrogel attained an effective absorption bandwidth (EAB) of 4.8 GHz and minimum reflection loss (RL_min) value of −55.6 dB. Moreover, GH frameworks facilitated heat transfer pathways, thus increasing the optimized thermal conductivity of the hydrogel from 0.634 W m⁻¹ K⁻¹ to 1.091 W m⁻¹ K⁻¹. The increase in the thermal conductivity, together with heat dissipation from water evaporation, led to a temperature drop of ∼10 °C in the simulating heater. Additionally, halloysite nanotubes formed a dense flame-retardant layer, ensuring the safety of the hydrogel under ultrahigh temperatures. Overall, these multifunctional hydrogels offer a promising solution to simultaneously address the challenges of heat accumulation and electromagnetic interference in electronics.