N-doped carbon@Cu core-shell nanostructure with nearly full solar spectrum absorption and enhanced solar evaporation efficiency

Solar steam generation has been considered an emerging technology for clean water generation with low energy consumption. Cu-based nanostructures as inexpensive and earth-abundant plasmonic absorbers show excellent light absorption and evaporation performance for solar steam generation. However, Cu nanoparticles present a narrow absorption peak in the visible region, and their photothermal stability is pernicious due to their high surface energy and low standard reduction potential. In this work, an N-doped carbon@Cu (NC@Cu) core-shell nanostructure was synthesized by the in situ heat treatment of polydopamine@CuO, which displays good light absorption in the full solar spectrum. Owing to the synergistic photothermal effect between N-doped carbon and Cu nanoparticles, the dry NC@Cu membrane exhibits a rapid photothermal response, and the surface average temperature reaches 51.5 °C after 30 s under one Sun illumination in air. When the height of the cold evaporation side surface is 6.0 cm, the NC@Cu membrane shows a superior evaporation rate of 2.76 kg m⁻² h⁻¹ and an evaporation efficiency of 137.1% under one Sun illumination, which is comparable to other state-of-the-art solar absorbers reported in the literature. This work demonstrates a new paradigm for a facile, stable, low-cost, and highly efficient solar desalination system.