From CdS to Cu ₇ S ₄ Nanorods via a Cation Exchange Route and Their Applications: Environmental Pollution Removal, Photothermal Conversion and Light‐Induced Water Evaporation

A detailed transformation process of cation exchange (CE) chemistry from hexagonal phase CdS to CdS‐Cu 7 S 4 core‐shell heterostructures nanorods and eventually to monoclinic phase Cu 7 S 4 nanorods is reported. Applications of the nanorods in environmental pollution removal, photothermal conversion and light‐induced water evaporation were investigated. The influence of the reaction time, morphology, and crystal phase on the photocatalysis, photothermal conversion and light‐induced water evaporation was discussed. The results showed maximum removal value of rhodamine B by 97.8% at 1 h timepoint. Aqueous dispersion of the core‐shell CdS‐Cu 7 S 4 heterostructures nanorods prepared with 2 h (1.0 g/L) exhibited a good photothermal conversion performance as it saw increase in sample temperature by 37.8 o C in 300 s under the irradiation of 980 nm laser. The exposure of as‐obtained sample film to simulated sunlight irradiation at 2 h (8 mg) increased the weight loss of pure water by 0.62 g in 30 min with the water evaporation efficiency up to 48.4%. We are reporting an excellent light‐induced water evaporation performance potential of the nanorods discussed.