Study of Cu3SbS4/Sb2S3 photothermal heterostructure coating for enhanced solar still desalination performance with durability analysis

Passive Solar Stills are an alternative method of producing fresh water in a decentralized manner. However, they suffer from being limited due to the low broadband solar absorptivity of typical basin materials. In this study we present the synthesis, characterization and photothermal assessment of a Cu 3 SbS 4 /Sb 2 S 3 (Famatinite/Stibnite) nano coating on a passive solar still absorber basin. The phase pure nanoparticles (18 nm) were synthesized using aqueous co-precipitation and subsequent calcination at 500 °C under Argon. The particles were then coated onto an acrylic substrate to form a uniform 55 µm coating (CSAS). Various characterizations were performed and results confirmed the presence of both phases within the crystalline structure. Under 1 sun irradiation, CSAS produced a constant water surface temperature of 58.7 °C, which was 14.0 °C greater than the uncoated acrylic surface (AS). A steady state evaporation rate of 2.06 kg m -2 h −1 which was 1.4 times higher than that of AS. It leads to cumulative mass loss of 5.67 and 4.15 kg m −2 from CSAS and AS, respectively. Outdoor testing of the modified solar still (MSS- coated with Cu 3 SbS 4 /Sb 2 S 3 ) compared to the uncoated reference (CSS) showed that MSS produced a daily fresh water output of 5.3 kg m −2 d -1 which was 65.6 % higher than CSS, with average thermal and exergetic efficiencies of 61.34 % and 2.36 %, respectively. After completing 30 cycles of accelerated desalination testing, CSAS had retained 96.0 % yield and 96.1 % thermal efficiency with accumulation of salt and minimal deterioration in coating durability, confirming Cu 3 SbS 4 /Sb 2 S 3 as a viable, sustainable photothermal absorber for use in passive solar desalination applications.