Asymmetric solar evaporator with salt-resistance capability for freshwater and energy generation

Solar-driven steam generation is a promising solution for addressing the pressing challenges of freshwater and energy scarcity, but the accumulation of salt on the evaporator surface hinders performance by reducing sunlight absorption and blocking water transport. To overcome this limitation, we developed an innovative Janus solar evaporator with asymmetric surface wettability that simultaneously generates energy and clean water. The solar evaporator-based niobium nitride (Nb4N5) nanosheets with broadband absorption and high light-to-thermal conversion capability displayed an excellent high evaporation rate of 2.30 kg m-2 h-1 under 1 kW m-2 irradiation, which was 4.8-fold higher than that of melamine foam evaporator. Notably, the Janus evaporators displayed an excellent evaporation rate of up to 2.10 kg m-2 h-1 in 20wt.% NaCl solution. Furthermore, during steam generation, the hybrid evaporator with a thermo-electricity module produced an open-circuit voltage of 135 mV and a short-circuit current of 14.6 mA under two sun irradiation. Our findings demonstrated that the Janus evaporator with salt-resistance property has significant potential for simultaneous steam and electricity production, offering a promising solution to simultaneously address the water and energy crisis.