Optimization of span distance in photoelectrothermal-based curved-type hydrophilic carbon fabric evaporators for...

Solar interfacial evaporation offers a sustainable route for seawater desalination but remains limited owing to solar availability. Here, a curved photoelectrothermal evaporator was fabricated using surface-modified hydrophilic carbon fabric supported by two melamine sponges. The curved configuration exposes both fabric surfaces and supplies water from both ends. Flat and curved evaporators were compared, and span distances of 3-6 cm were systematically evaluated. The treated carbon fabric absorbed a water droplet within 100 ms and exhibited more than 85% light absorption over 200-2500 nm. A span distance of 4 cm provided the best balance among solar absorption, joule heating, and capillary water transport. Under 1 sun and an applied voltage of 3 V, the optimized 8 cm × 2 cm evaporator achieved evaporation rates of 7.81 kg m⁻² h⁻¹ for deionized water and 7.23 kg m⁻² h⁻¹ for 3.5 wt% artificial seawater. Five consecutive saline-water tests using the same specimen, with water rinsing between cycles, retained approximately 99% of the initial evaporation rate. Outdoor tests yielded water collection rates above 3 kg m⁻² h⁻¹, while the major-ion concentrations in the collected water were reduced by three to four orders of magnitude. These laboratory and outdoor test results identify span distance as a key design parameter for curved photoelectrothermal evaporator and demonstrate recoverable seawater desalination with rinsing.