In-situ upcycling of cadmium from wastewater into core–shell ZnS@Zn0.58Cd0.42S heterojunction photocatalyst for environmental purification and H2 evolution

• Microalgae-derived yolk-shell microspheres were prepared to achieve Cd 2+ upcycling. • Cd 2+ from wastewater was directly in-site converted into photocatalyst (ZSC) • ZSC was demonstrated to have core-shell ZnS@Zn 0.58 Cd 0.42 S heterostructure. • ZSC shows excellent performance for H 2 evolution and organic pollutant degradation. • Photocatalytic activity of ZSC was enhanced due to heterojunction. Uncontrolled exploitation of heavy metals has caused environmental pollution and mineral resource depletion crises. The first-choice approach for addressing these issues is heavy metal upcycling. However, efficient retrieval and conversion of heavy metals from contaminated environments into high-value-added products remains challenging. Here, we developed a strategy to simultaneously achieve efficient accumulation (256 mg/g), magnetic separation (∼1 min), and directly in-site conversion of Cd 2+ from wastewater into core-shell ZnS@Zn 0.58 Cd 0.42 S heterojunction photocatalysts (ZSC). Microalgae-derived yolk-shell microspheres containing multicomponent nanocores (Fe 3 O 4 and ZnS) were developed to serve as adsorbent, magnetic carrier, and photocatalyst assembly platform to achieve Cd 2+ upcycling into ZSC. In particularly, ZSC shows much higher photocatalytic activity for H 2 generation and organic pollutant degradation than do commercial photocatalysts (P25-TiO 2 and CdS) due to its greater utilization of solar energy and heterostructure. Altogether, we provide an appealing strategy for upcycling cadmium into high-performance heterojunction photocatalysts for environmental purification and clean energy generation.