All-day multifunction hygroscopic salt/aerogels/photocatalysts system for efficient freshwater-hydrogen-oxygen co-production from air

Atmospheric water harvesting and photocatalytic water splitting are effective methods for solar-driven water collection, hydrogen, and oxygen production, essential for tackling energy scarcity. However, most research treats these methods separately, further limiting their diversified energy conversion. Here, we synthesize novel nitrogen vacancies carbon nitride/oxygen vacancies bismuth vanadate (N_v-CN/O_v-BVO) photocatalysts with enhanced light absorption and efficient charge transfer, leading to improved photocatalytic performance. Coupling of these photocatalysts and LiCl within rGO aerogels, a multifunction system is constructed from LiCl/rGO/N_v-CN/O_v-BVO for simultaneous production of freshwater-hydrogen-oxygen. Along with porous transport channels, enables the system to achieve synergetic effects of multi-dimensional mass transfer for rapid moisture absorption-desorption, water transport, and gas diffusion. Water collection and hydrogen production rates have been revealed to increase synergistically with enhanced water uptake, resulting from the increased relative humidity (RH). The system displays the water uptake of 1.9 g g⁻¹ at 50% RH, and 1.6 g g⁻¹ water collection, 28.9 µmol h⁻¹ H₂ production, 14.2 µmol h⁻¹ O₂ production under 100 mW cm⁻² illumination. A large-area device collects 1.5 g g⁻¹ water, and produces the 460 µmol hydrogen and 227 µmol oxygen during the daytime in a mild atmosphere, maintaining operational stability for 7 days.