Hydrothermally Derived Hydrochar from Waste Sawdust for Solar Vapor Generation

Herein, hydrochar is derived from abundant and low‐cost waste sawdust using hydrothermal carbonization in distilled water with a series of temperatures (150, 200, and 250 °C) and time (2 and 3 h), where the hydrochar characteristics are evaluated toward its application as a solar absorber. The hydrochar‐based solar absorber is fabricated and tested using outdoor solar vapor generation under direct solar radiation with an average solar intensity of 1.26 kW m−2. The solar absorber incorporated with hydrochar is derived at 250 °C for 3 h and displays the best average efficiency (71.35 ± 0.90%) and evaporation rate (1.30 ± 0.04 kg m−2 h−1). The collected clean water salinity (below 300 ppm) and pH (6.72–7.23) from the solar absorber is within the safe drinking water limit by the World Health Organization. Therefore, the hydrochar‐based solar absorber can be used to generate clean water from seawater desalination using solar vapor generation.