Pyrolyzed moringa seed-based photothermal absorber for enhanced solar interfacial evaporation

Developing cost-effective photothermal materials for solar-driven water evaporation is essential for attaining high evaporation rates with simplicity and affordability, particularly in arid regions. However, the preparation of photothermal materials involves the use of costly materials and complex synthesis procedures, which may limit scalability. This study presents a twofold objective: the use of biomass-based materials as photothermal absorbers and a straightforward preparation method that eliminates the need for costly and complex processes. The biochar production was optimized at 41.4 % yield when pyrolyzed at 300 °C for 60 min. The resulting biochar moringa seeds (BMS) were used as a photothermal absorber in the interfacial solar evaporation system. BMS demonstrated impressive water evaporation performance, achieving an evaporation rate of 6.72 kg m⁻² h⁻¹ at steady state under infrared light, which represents a 72.75 % improvement compared to untreated cotton (UC). Meanwhile, the moringa seed (MS) and UC cases demonstrated evaporation rates of 4.24 and 3.89 kg m⁻² h⁻¹ at steady state, respectively. In terms of thermal performance, the dry BMS case reached a temperature peak of ∼134 °C within 6 min, but the wet BMS reached ∼78.5 °C after 20 min of illumination. This study underscores a sustainable and efficient approach to solar-driven water evaporation by utilizing biomass materials, offering practical applications in water-scarce and arid regions.