High-entropy-alloy nanoparticles with 21 ultra-mixed elements for efficient photothermal conversion

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 due to the strong immiscibility among the repelling combinations. Here, assisted by an extremely high evaporation temperature, ultra-fast cooling and vapor-pressure strategy, the arc-discharged plasma method was employed to synthesize ultra-mixed multi-metallic nanoparticles composed of 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 of >92% in the entire solar spectrum (250 to 2500 nm). In particular, the 21-element nanoparticles achieve a considerably high solar steam efficiency of nearly 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 creates a new strategy for uniformly mixing multi-metallic elements for exploring their unknown properties and various applications.