Durable, scalable and affordable iron (III) based coconut husk photothermal material for highly efficient solar steam generation

Biomass-based photothermal materials, being fabricated based on agricultural waste, are widely applied in solar steam generation (SSG) recently. The evaporation rate of the SSG systems while utilizing these materials can reach 1.4-1.6 kg m-2 h-1 under 1 sun condition. In this study, a coconut husk (CH), a common agricultural waste, was utilized to fabricate the photothermal material that can be applied in the SSG system. CH consists of coconut fibers containing many vascular bundles with 10-20 mu m diameter and cocopeat that has honeycomb-like structure. After treating CH with tannic acid and Fe (III) solution, the coordination of phenolic compounds with Fe3+ in the CH is formed. The resulting CH-TA-Fe3+ (CHP) material demonstrated significant advantages such as high light absorption, low thermal conductivity, ultra-fast water transportation, low moisture enthalpy, and self-cleaning properties. The CHP-based SSG system possessed high seawater evaporation rate (1.83 kg m-2 (1)) and evaporation efficiency (73.2%), which are comparable to those in the previous studies on biomass material based SSG systems. Especially, the CHP-based SSG system exhibited excellent structural stability that ensures their long-term performance in the seawater desalination. With simple fabrication process, affordable price, and eco-friendly materials, the CHP proves great potential in seawater desalination application.