Watermelon Pulp Templated Polypyrrole for Solar Steam Generation with High Photothermal Conversion Efficiency

Efficient utilization of solar energy for solar steam generation is an effective way to tackle the shortage of fresh water resources. However, the utilization of solar steam evaporators often suffers from a series of problems, such as high cost, complex processes, and low conversion rate, which seriously hinders the development of solar steam devices. Here, a polypyrrole/watermelon pulp (WPPY) evaporator, which is based on soaking freeze-dried lumpy watermelon pulp (WP) in pyrrole solution, initiating polymerization in the ice bath, followed by heat-treatment to achieve an efficient solar steam generation (SSG) device, is designed and produced. The WPPY with a pyrrole to WP mass ratio of 1:2 (WPPY-3) exhibits a developed porous structure, superior hydrophilicity, relatively small thermal conductivity (0.0375 W m−1 K−1, a simple one-step fabrication process, and superior light absorption (94.7%). Its evaporation rate reaches 1.64 kg m−2 h−1 without additional insulation, while the light-to-heat conversion efficiency reaches 96.1% under one solar irradiation (1 kW m−2) at the same time. Additionally, it also shows good durability. This environmentally friendly and stable photothermal conversion composite material that shows good cycle stability has great potential for applications in seawater desalination via SSG.