Confined high-entropy-alloy nanoparticles within graphitic shells for synergistically improved photothermal conversion

High-entropy-alloy nanoparticles (HEA-NPs) have exhibited great potential in solar steam generation, in which their photothermal conversion performances can be optimized through the interband transition (IBTs) between the composing elements. In this work, the HEA-NPs were in-situ confined in the multi-layer graphitic shells (HEA@C NPs) by the arc-discharged plasma approach to achieve a synergistic improvement in the solar steam generation performances. It can be recognized that the graphitic shells not only serve as optical absorbers but also improve the surface temperature ascribed to their low thermal conductivities. The numerical simulation reveals that the electric fields can be accumulated in the graphitic shells over the wavelength regions of 1000 to 2500 nm. As a result, the most optimized FeCoNiTiVCrMnCu@C nanocapsules demonstrated an evaporation rate of 2.66 kg m ⁻² h ⁻¹ under one sun irradiation with an energy conversion efficiency of 98%, and the surface temperature can increase to ∼105 °C within 90 s, demonstrating an effective solar steam generation performance. The present study indicates an insight into the synergistic optical absorption behaviors between HEA-NPs and graphitic shells, and the nanocapsules could be expanded to other solar-thermal conversion applications.