A salt-rejecting anisotropic structure for efficient solar desalination via heat-mass flux decoupling

Solar evaporation is regarded as a promising and sustainable technology to address global clean water crisis. Tremendous efforts have been made for the development of new materials and structures, but heat utilization efficiency and stable salt-rejection remain the major challenges. In this study, a novel sugarcane-derived anisotropic structure with heat-mass flux decoupling effects was invented, and it exhibited outstanding salt-rejection and high efficiency in solar desalination. Numerical simulations revealed that heat-mass flux decoupling was achieved by making the mass flux perpendicular to the heat flux. The horizontally distributed channels provided sufficient water flux towards evaporation surface while transporting the concentrated salt ions from the surface back to the bulk water driven by the concentration gradient. Moreover, temperature gradient-driven heat transfer was effectively suppressed owing to the discontinuous and deficient water flux in the vertical direction. This anisotropic structure showed high efficiency (>80%) and excellent salt-rejecting performance for a wide range of salinities (0-15 wt%) and different solar densities (0.8-3 sun). Furthermore, stable performance was observed during long-term evaporation experiments under harsh operating conditions.