Beyond lotus: Plasma nanostructuring enables efficient energy and water conversion and use

Abstract Over millions of years, natural evolution created intricate plant microstructures to most effectively convert and use energy and water. Here we use one-step plasma carbonization and surface nanostructuring of microscopic textures of sacred lotus (Nelumbo nucifera), to dramatically surpass its natural performance in light harvesting, water transport and evaporation. The plasma exposure produces vertically-oriented graphenes (VGs) on the lotus micro-textured surfaces (lotus/VG), without any external carbon source. The nanostructures exhibit high photonic absorption of 99.2% (~twice the pristine lotus), customized centralized water pathway, run-through channels and super-hydrophilicity for ultrafast water transport (~5 times the pristine lotus), and potential for scalable, low cost production. The lotus/VG evaporator exhibits a high solar energy conversion efficiency (~90%) at 1 sun, competitive with synthetic materials. Furthermore, the lotus/VG nanostructures are applied for sludge drying and wastewater treatment, demonstrating great potential of this nanotechnology-enhanced natural material for renewable solar energy utilization.