Design of a bifunctional Janus structure for high efficiency solar distillation in hypersaline brine

Abstract

In solar desalination, resolving the durability and efficiency losses stemming from salt precipitation has become a long sought-after goal. We showcase the design for a facile, yet high efficiency solar distillation device that exhibits durable operation in hypersaline brine, where a bifunctional Janus structure is introduced for self-driven salt resistance and photothermal conversion. A Janus scaffold was constructed using an acrylate hydrogel and polyvinylidene difluoride (PVDF) for self-driven salt resistance; the polyelectrolyte effect of the gel prevents ion accumulation and the hydrophobic PVDF suppresses ion diffusion to the evaporative interface. Then, the hydrophobic part was functionalized with a new light absorber, a Ni/C nano-composite, to achieve effective photothermal conversion across the full solar spectrum. The evaporator is capable of 14 days of continuous working in hypersaline brine (10 wt% NaCl) at a rate of 1.56 kg m⁻² h⁻¹, which is among the best reported durabilities and approaches the theoretical limit. Hopefully, the new design will greatly expand the ability of solar desalination to work in extreme environments.