摘要： Photothermal materials are crucial for maximizing the solar energy in solar steam generation. The conventional photothermal materials have limited absorption broadband, complicated manufacture, expensive cost and difficulty in scaling up. To remedy this dilemma, we herein propose a novel cost-effective nanodiamonds(NDs) paint-coat using filter papers (FPs) as a supporting scaffold. The phy-chemical characterizations of samples like morphology, structure and optical properties indicate that the NDs paint-coat has bandwidth absorption, porous network structure, and high absorption ability. For the sake of evaluating their practical applications, NDs paint-coat and 3D conical structures were further designed to constitute a 3D-interfacial solar steam generation (3D-ISSG). Owing to the rationally 3D structure, the heat loss and optical loss have been effectively restrained through optimized heat management within the 3D-ISSG. The experimental results show that the solar thermal conversion efficiency of 3D-ISSG was achieved up to 82.97 % for evaporation under one sun illumination (1 kW/m2), which is about 4.16 times as high as the pure water. Moreover, the 3D-ISSG performs reliable reusability after 15 cycling experiments under 1 kW/m2 solar illumination, indicating its broad application prospect for new energy devices, seawater desalination and water treatment.