Photothermal materials with broadband optical absorption and high conversion efficiency are intensively pursued to date.H ere,p roposing by the d-d interband transitions,w er eport an unprecedented high-entropya lloy FeCoNiTiVCrCu nanoparticles that the energy regions below and above the Fermi level (AE 4eV) have been fully filled by the 3d transition metals,w hich realizes an average absorbance greater than 96 %i nt he entire solar spectrum (wavelength of 250 to 2500 nm). Furthermore,w ea lso calculated the photothermal conversion efficiency and the evaporation rate towards the steam generation. Due to its pronounced full light capture and ultrafast local heating, our high-entropy-alloy nanoparticle-based solar steam generator has over 98 %efficiency under one sun irradiation, meanwhile enabling ah igh evaporation rate of 2.26 kg m À2 h À1 .

Designing heterogeneous interfaces and components at the nanoscale is proven effective for optimizing electromagnetic wave absorption and shielding properties, which can achieve desirable dielectric polarization and ferromagnetic resonances. However, it remains a challenge for the precise control of components and microstructures via an efficient synthesis approach. Here, the arc‐discharged plasma method is proposed to synthesize core@shell structural high‐entropy‐alloy@graphite nanocapsules (HEA@C‐NPs), in which the HEA nanoparticles are in situ encapsulated within a few layers of graphite through the decomposition of methane. In particular, the HEA cores can be designed via combinations of various transition elements, presenting the optimized interfacial impedance matching. As an example, the FeCoNiTiMn HEA@C‐NPs obtain the minimum reflection loss (RLmin) of −33.4 dB at 7.0 GHz (3.34 mm) and the efficient absorption bandwidth (≤−10 dB) of 5.45 GHz ranging from 12.55 to 18.00 GHz with an absorber thickness of 1.9 mm. The present approach can be extended to other carbon‐coated complex components systems for various applications.

Multi-metallic nanoparticles have been proven to be an efficient photothermal conversion material, for which the optical absorption can be broadened through the interband transitions (IBTs), but it remains a challenge to make the composition homogeneous distributing within the immiscible combinations. Here, assisted with the extreme-high evaporated temperature, ultra-fast cooling, and vapor-pressure strategy, the arc-discharged plasma method was employed to synthesize the ultra-mixed multi-metallic nanoparticles compositing with 21 elements (FeCoNiCrYTiVCuAlNbMoTaWZnCdPbBiAgInMnSn), in which the strongly repelling combinations were uniformly distributed. Due to the reinforced lattice distortion effect and excellent IBTs, the nanoparticles can realize an average absorption greater than 92% in the entire solar spectrum (250 to 2500 nm). In particular, the 21-element nanoparticles achieve a considerably high solar steam efficiency of near 99% under one solar irradiation, with a water evaporation rate of 2.42 kg m−2 h−1, demonstrating a highly efficient photothermal conversion performance. The present approach opens a new strategy for uniformly mixing multi-metallic elements for exploring their unknown properties and various applications.