A bioinspired 3D solar evaporator with balanced water supply and evaporation for highly efficient photothermal steam generation

Abstract

Interfacial solar steam generation (ISSG) is a promising and energy-efficient strategy for freshwater generation. However, the balance between the demand and supply of water at the surface of photothermal materials is usually ignored, leading to a mismatch between the absorbed solar energy and the solar energy required for water evaporation. This reduces the energy conversion efficiency which limits water steam generation. To address this issue, inspired by a lotus leaf (with a trunk to branch water supply system), a 3D carbon fibre-cotton-based cone (CFC-Cone) evaporator with tunable water supply is well designed herein via the traditional basket-weaving strategy. By changing the number of branch water paths, an equilibrium between the water supply flux and evaporation rate can be realized to optimize the energy distribution on the surface of carbon fibres. The as-designed 3D CFC-Cone evaporator can efficiently harvest incident sunlight with an evaporation rate of 3.27 kg m⁻² h⁻¹ and a photothermal conversion efficiency of 194.4% under one sun illumination. This work provides a perspective on the design of ISSG by optimizing the 3D structure to balance water transport and evaporation for energy-efficient steam.