Scalable Solar Evaporator Based on Bandgap Engineered CuMnCrO4 Spinel Oxide with Salt-Resistant Property for Contaminated Seawater

Abstract

Freshwater scarcity demands innovative solutions that combine efficiency, durability, and scalability. Here, CuMnCrO4 (CMCO), is presented as a ternary spinel oxide photothermal absorber introduced for the first time in solar desalination, synthesized via co-substitution of Mn3O4 with Cu and Cr. This multi-cation design narrows the bandgap from 2.3 to 1.49 eV, markedly enhancing solar absorption across the visible and near-infrared spectrum and enabling efficient light-to-heat conversion. Unlike conventional carbon or single-oxide-based systems, CMCO demonstrates record-high evaporation performance of 4.1 kg m-2 h-1 under 1-sun, positioning it among the most efficient oxide-based ISSG materials reported to date. Equally novel is the integration of CMCO with a cotton fabric substrate and hydrophobic polyester strips in an inverted U-shaped configuration, which ensures continuous water wicking, localized salt separation, and mechanical robustness. This architecture delivers stable operation over three weeks without salt accumulation, overcoming a long-standing challenge in ISSG. Furthermore, the system retains high efficiency under strongly acidic/alkaline conditions and in oil- or dye-contaminated water, demonstrating unique resilience rarely reported in solar desalination systems. Finally, the modular design enables straightforward scalability from laboratory-scale strips to large-area panels. Together, these advances establish CMCO-based systems as a new materials platform for practical, durable, and scalable solar desalination, offering a sustainable pathway toward addressing global water scarcity.