Thermal‐Ionic Coupling in Transpiration‐Inspired Janus Nanofiber Membranes: Synergistic Dry‐Wet Interface Engineering for Solar‐Driven Electricity Generation

ABSTRACT

Harnessing solar evaporation for simultaneous steam and electricity generation is an emerging technology for sustainable energy‐water systems, yet its development is fundamentally constrained by the inability to maintain a stable interfacial potential gradient in homogeneous materials. Here, we introduce a dry‐wet interface engineering strategy that enables persistent thermal‐ionic coupling for continuous electricity generation. Inspired by leaf transpiration, an asymmetric Janus nanofiber membrane is constructed to form a stable hydrophilic‐hydrophobic interface that simultaneously regulates fluid distribution and interfacial charge dynamics. This architecturally confined interface induces hydration‐triggered surface ionization on the hydrophilic layer, generating an intrinsic potential difference continuously reinforced by evaporation‐driven directional ion transport. As a result, the Janus evaporator delivers a stable open‐circuit voltage of 0.22 V under 1 sun illumination, 57% higher than natural evaporation, and exhibits scalable output up to 2.21 V via modular integration. Mechanistic investigations combining experiments and multiscale simulations reveal that the sustained electrical output arises from the synergistic coupling of interfacial potential modulation, ion‐selective transport, and localized photothermal heating. The dry‐wet interface plays a decisive role by stabilizing charge separation and suppressing potential dissipation. This work establishes a general framework for interfacial potential engineering in evaporation‐driven systems, enabling simultaneous solar desalination and electricity generation.