Highly Efficient Solar Steam Generation by Glassy Carbon Foam Coated with Two-Dimensional Metal Chalcogenides

Steam generation by eco-friendly solar energy has immense potential in terms of low-cost power generation, desalination, sanitization, and wastewater treatment. Herein, highly efficient steam generation in a bilayer solar steam generator (BSSG) is demonstrated, which is comprised of a large-area SnSe-SnSe₂ layer deposited on a glassy carbon foam (CF). Both CF and SnSe-SnSe₂ possess high photothermal conversion capabilities and low thermal conductivities. The combined bilayer system cumulatively converts input solar light into heat through phonon-assisted transitions in the indirect band gap SnSe-SnSe₂ layer, together with trapping of sunlight via multiple scattering due to the porous morphology of the CF. This synergistic effect leads to efficient broadband solar absorption. Moreover, the low out-of-plane thermal conductivities of SnSe-SnSe₂ and CF confine the generated heat at the evaporation surface, resulting in a significant reduction of heat losses. Additionally, the hydrophilic nature of the acid-treated CF offers effective water transport via capillary action, required for efficient solar steam generation in a floating form. A high evaporation rate (1.28 kg m^-2 h^-1) and efficiency (84.1%) are acquired under 1 sun irradiation. The BSSG system shows high recyclability, stability, and durability under repeated steam-generation cycles, which renders its practical device applications possible.