Gradient-aligned Au/graphene meshes with confined heat at multiple levels for solar evaporation and anti-gravity catalytic conversion

Abstract

As solar energy is readily available in most climates, solar evaporation plays a critical role in freshwater production and can be further integrated into various important applications. Demonstrated here is a plasmonic-antenna-coupled aerogel with confined heat at the micro and nanoscale levels based on vertically aligned Au/N-doped reduced graphene oxide (N-RGO) meshes towards an effective solar evaporation. The gradient microchannels in the aerogel were ably constructed by introducing gradient anti-freeze (i.e., NH₄OH) concentrations in the hydrogel before freeze-drying to concentrate water to a central region (i.e., the hot zone). As plasmonic nanoantennas, Au nanoparticles were integrated on N-RGO meshes in/around nanopores to enhance energy harvesting and accurately localize heat for promoted in situ evaporation. Featuring broadband absorption (99.7%) and plasmon-enhanced photothermal conversion, this aerogel exhibits superior solar-to-vapor conversion (97.1%) and a high evaporation rate (2.72 kg m⁻² h⁻¹, normalized to both top and side surfaces), along with salt-resistance. Besides, the aerogel has been demonstrated as a novel solar-driven, anti-gravity catalytic reactor toward high value-added chemical (e.g., 4-aminophenol) conversions with high efficiency by localizing heat on reaction sites. This work provides an attractive strategy for the elegant manipulation of water and energy at multi-levels in solar evaporation and shows a novel approach to anti-gravity catalytic conversions driven by sunlight.