Solid-Phase Upcycling Toward the Production of Ultrahigh-Loading Single-Atom Catalysts

The recovery of valuable transition metals from deactivated catalysts is crucial for alleviating the challenges of resource scarcity and environmental pollution. Guided by AI-powered big data analysis, we identified an important research gap in the sustainable recovery of early transition metals and proposed a solid-phase upcycling strategy to transform waste catalysts into highly valuable single-atom catalysts (SACs). This involves a heat-induced redispersion of metal aggregates into single atoms on the polycrystalline carbon nitride (PCN) support, producing highly active M₁-PCN SACs up to 20 wt% (M = Cu, Fe, Co, and Ni). Subsequent techno-economic analysis confirms a two-thirds reduction in production cost and greenhouse gas emissions compared to conventional hydrometallurgical and pyrometallurgical processes, thus paving a new path in the development of sustainable technologies for metal recovery.