A light-trapping conical TaN-PPy photothermal evaporator with convection-driven salt rejection for sustainable solar desalination

The water scarcity crisis in the developing world creates an immediate need for cost-effective, environmentally friendly water treatment methods. Interfacial solar evaporation is one of the promising ways of dealing with this problem using renewable solar energy. The challenge associated with this field is developing an advanced photothermal absorber with capabilities for wide-bandgap solar absorption, efficient water–air interface thermal management, fast capillary water transport, and good stability. Herein, we introduce a cone-shaped photothermal evaporator device based on a combination of plasmonic tantalum nitride (TaN) nanoparticles and a conducting polypyrrole (TaN-PPy) nanocomposite on a hydrophilic cotton surface. The TaN nanoparticles possess a high possibility of absorbing a wide wavelength of light based on localized surface plasmon resonance effects, and the PPy network can support charge transfer, improve interface stability and allow for simple device production by a spray-coating technique. Such a synergistic design leads to a highly efficient evaporation setup. Under 1 sun irradiance of 1 kW m −2 , an excellent evaporation rate of 1.8 kg m −2  h −1 and a high solar-to-vapor conversion efficiency of 84% are obtained for the optimized TaN-PPy fabric. Moreover, it displays high stability in a continuous testing setup and efficiently desalinates simulated seawater, with a reduction in salinity above 99.9%. This work provides a practical and scalable design for efficient, long-term solar desalination and wastewater treatment.