Flower-shaped hierarchical CuO nanostructures for efficient solar desalination

[Display omitted] •Developed a scalable and efficient 3D SSG using hierarchical CuO nanoflower arrays.•97% solar absorption due to CuO’s narrow bandgap and anti-reflective structure.•Efficient water wicking and vapor escaping via superhydrophilic CuO microchannels.•Achieved a high evaporation rate of 1.80 kg m−2h−1 under 1-sun irradiation.•Demonstrated freshwater production using a salt-resistant CuO-based 3D ISSG. Desalination technology utilizing solar energy conversion has gained significant attention as an efficient and sustainable solution to potential future water shortages. In particular, interfacial solar steam generation using superior light-absorbing materials has made considerable progress. However, several challenges still remain for practical applications, including low productivity, incomplete light absorption, and significant heat loss. In this study, we demonstrate a novel three-dimensional solar steam generator based on hierarchical copper oxide nanoflower array, which exhibits outstanding thermal energy conversion efficiency. The CuO nanostructures possess broad and strong light-absorption capabilities over the entire solar spectrum due to their narrow band gap (1.2 eV) and gradual refractive index profile. Moreover, the 3D SSG not only provides an extensive evaporative surface area and vapor escape pathways via superhydrophilic microchannels, but also harvests the emitted radiation and ambient latent heat. As a result, the 3D SSG achieved an impressive solar-weighted absorption of 97 % and a high evaporation rate of 1.80 kg m−2h−1 under 1-sun solar irradiation. This study presents a promising approach for economical and efficient freshwater production through the demonstration of a hierarchical CuO NFA-based 3D evaporator.