Facile Preparation of MnO₂-Deposited Wood for High-Efficiency Solar Steam Generation

Wood, a natural renewable material, has drawn great attention in solar steam generation in recent years due to its intrinsic properties such as high hydrophilicity and low thermal conductivity. Until now, great achievements have been made in increasing the light absorption of wood-based solar evaporators, mainly through surface carbonization and coating. However, the complicated and cost-intensive preparation process of the light absorption layer prevents its large-scale application. In particular, the carbonized and coated surface could be importantly influenced by the scouring effect of waves and the corrosion of salt water. Herein, a facile, low-cost, and scalable in situ reduction method has been developed to prepared KMnO4 oxidized wood (K-wood) for solar steam generation, which not only shows high evaporation performance but also has high structural stability. In the preparation process, the reaction-product black MnO2 particles will be uniformly distributed on the surface of wood, making the K-wood exhibit a high solar absorbance of about 94%. Moreover, the K-wood could still maintain the inherent high hydrophilicity and excellent thermal insulation performance. Benefitting from all of these advantages, the K-wood achieved a high evaporation rate (1.22 kg m–2 h–1) and a high evaporation efficiency (81.4%) under 1 sun illumination (1 kW m–2). Importantly, the K-wood also exhibits excellent structural stability, such as having good acid–base resistance and also washing resistance, and could even withstand an ultrasound treatment for even 2 h. The reusability of the K-wood was also tested, and the evaporation rate remains nearly unchanged after 20 cycles in seawater evaporation. Moreover, the condensate water obtained by the homemade collection device shows low ion concentrations, demonstrating that the K-wood possesses an excellent ability in seawater desalination treatment. This study provides a simple method to manufacture a high-strength wood-based solar steam evaporation device, which has potential for future large-scale applications.