Decoupling Mass Transport Conflicts in Solar Driven Water‐Salt Co‐Production via Heterogeneous Evaporation Interface

Abstract Efficient water‐salt co‐production is crucial for treating high‐concentration brine, yet remains challenging due to conflicting mass transport demands. High evaporation rate requires enhanced mass transfer to achieve salt tolerance, whereas high salt production rate demands restricted transport for salt nucleation. Due to the inherent mass transport conflict, current reported homogeneous evaporation interfaces with single mass transfer properties create a wide water‐salt interference area, resulting in inevitably low water‐salt co‐production performance. Herein, this study develops a solar evaporator with a heterogeneous evaporation interface (HE‐EI) that achieves an impressive evaporation rate of 3.36 kg·m ⁻² ·h ⁻¹ and salt production rate of 0.52 kg·m ⁻² ·h ⁻¹ for high‐concentrated brine (20 wt.% NaCl) under 1 kW·m ⁻² illumination, outperforming reported water‐salt co‐production evaporators. Experimental results and theoretical analyses demonstrate that the HE‐EI has a very narrow water‐salt interference area, effectively decoupling mass transport conflicts and thereby achieving superior water‐salt co‐production performance. Notably, when the solar evaporator with HE‐EI is used for lithium extraction from salt‐lake brine, the enrichment rate of Li ⁺ is 240 times higher than simulated evaporation ponds, enabling Li salt crystallization within the salt‐producing area. Overall, this HE‐EI addresses the long‐standing conflicts between water‐salt co‐production, opening a scalable pathway toward the global challenge of high‐concentration brine treatment.