Full-spectrum flatband photothermal evaporators with superhydrophilic vertical nanochannels for efficient solar steam generation

Abstract

Solar-driven interfacial evaporation technology offers a sustainable and efficient approach to seawater desalination. Achieving high-performance evaporation requires synergistic optimization of light absorption, water supply, vapor escape channels, and thermal management. In this work, we present a vertically aligned black titanium dioxide (TiO₂) nanotube array evaporator (denoted as BTT), synthesized via a hydrothermal reaction using titanium foam as the substrate. The evaporator exhibits exceptional photothermal conversion, localized thermal effects, and nano-confined water evaporation. The nano-confined effect within the vertical nanotube channels disrupts and reconstructs the hydrogen-bonding network of water, promoting the formation of “intermediate water” clusters that substantially reduce the intrinsic enthalpy of evaporation. As a result, the BTT evaporator achieves an outstanding evaporation rate of 2.48 kg m⁻² h⁻¹ under 1 sun illumination in 3.5 wt% simulated seawater. In addition, it demonstrates excellent long-term operational stability. This work presents a novel strategy for designing high-efficiency evaporators suitable for diverse environmental conditions.