Chemical‐Gradient‐Induced Marangoni Flows Boost Solar‐Brine Desalination and Enable Concurrent Power Generation

ABSTRACT Solar‐driven interfacial evaporation offers decentralised freshwater production with concurrent electricity generation, yet capillary‐driven water supply imposes a kinetic ceiling in high‐flux or high‐salinity conditions, where boundary‐layer buildup drives salt accumulation and performance decay. Here we establish a dual‐driving transport regime that couples capillary flow with chemically induced Marangoni convection in low‐tortuosity, vertically aligned channels. A longitudinal gradient of oxygen‐containing functional groups, introduced into a graphene‐oxide aerogel by thermal‐gradient reduction, generates a persistent surface‐tension disparity that sustains Marangoni microcirculation, continuously refreshing the evaporation interface by displacing concentrated boundary layers into the bulk. A miniaturised evaporator achieves 540 kg m − 3 h − 1 (2.7 kg m − 2 h − 1 ) in 20 wt% NaCl under 1‐sun illumination, sustaining stable operation for 12 h without observable salt accumulation, while simultaneously delivering a short‐circuit current of 25 µA and an open‐circuit voltage of 0.7 V. Series‐integrated devices directly power an LED. These results demonstrate that chemical‐gradient programming can recruit Marangoni convection as a robust co‐driver to surpass capillary‐limited transport, offering a generalizable strategy for high‐flux brine desalination with concurrent energy harvesting.