Densely distributed Co onto carbon-layer-coated flower-like Ni/Al₂O₃ and its tailored integration into a stirrer for multiple catalytic degradation and solar-powered water evaporation

Multiple functional tailored materials have shown great potential for both pollutant degradation and freshwater recovery. In this study, we synthesized densely distributed Co onto carbon-layer-coated Ni/Al₂O₃ hydrangea composites (Ni/Al₂O₃@Co) <i>via</i> the polymerization of dopamine under a controlled graphitized process. The characterization results revealed that Ni/Al₂O₃@Co, with abundant exposed bimetallic Co-Ni species on the surface of Al₂O₃, could afford accessible catalytic sites for persulphate activation and subsequent pollutant degradation. The tetracycline (TC) degradation rate of optimal Ni/Al₂O₃@Co₅₀₀ reached 98.1% within 15 min with a first-order rate constant of 0.498 min^-1, which is ∼1.38 times that of Al₂O₃@Co₅₀₀ (0.362 min^-1), indicating the existing Co-Ni intermetallic synergy. Free radical quenching experiments indicated that ˙O₂^- plays a leading role in the catalytic degradation of TC. Moreover, Ni/Al₂O₃@Co₅₀₀ afforded strong flexibility for the degradation of methylene blue (MB), norfloxacin (NFX), bisphenol A (BPA), and oxytetramycin (OTC). Ni/Al₂O₃@Co₅₀₀ catalysts were anchored onto a customized sponge <i>via</i> a calcium-triggered hydrogel crosslink strategy to construct an integral and tailored stirrer, which was used directly as the mechanical stirrer catalyst for the activation of peroxymonosulfate and pollutant removal. This obtained stirrer was also used as a monolith evaporator affording an evaporation rate of 1.944 kg m^-2 h^-1 at a solar-driven photothermal interface. We also demonstrated that the shape of the tailored sponge weakly affects the course of the degradation reaction. Furthermore, the degradation rates of TC in actual water sources on a Ni/Al₂O₃@Co₅₀₀ sponge were still maintained up to 90% with rational recycling properties, which provide a promising solution for the multiple-functional pollutant degradation and water regeneration.