Sustainable photothermal films from waste cigarette butts: A high-efficiency solar steam generator for freshwater production

The utilization of renewable solar energy for freshwater production via water evaporation presents a promising solution to freshwater shortages. In this study, we developed a novel photothermal film (CEM) derived from discarded cigarette butts, which was nitrogen-modified by using urea to serve as a water-conducting layer, thereby enhancing hydrophilicity and water transport efficiency. The in-situ incorporation of black humic acid (BHA) on CEM further improved solar energy absorption, significantly enhancing the photothermal performance. As a result, the CEM-based solar steam evaporator achieved an excellent water evaporation rate of 2.12 Kg·m −2 ·h −1 under 1 KW·m −2 illumination with a solar-to-steam conversion efficiency exceeding 90 % and excellent reusability. Additionally, outdoor experiments and simulated seawater desalination tests confirmed its practical applicability for efficient seawater desalination. More importantly, this study verified the critical role of the hydrophilicity of the water-conducting layer in the evaporation rate. This work provides a novel strategy for developing high-performance photothermal films for solar steam generation, not only facilitating the sustainable recycling of waste cigarette butts, but also achieving efficient freshwater production. • A solar evaporator was developed using nitrogen-modified waste cigarette butts (CEM) and composited black humic acid (BHA). • The [email protected] U/CEM film exhibited an excellent photothermal conversion and water evaporation performance. • This work offers a sustainable strategy to recycle cigarette butts for freshwater production.