Dynamic Co/Ce Redox Coupling in Halloysite Nanotube-Supported Au Nanoreactors Accelerates Selective Detoxification of Nitroaromatic Wastewater

Abstract The catalytic reduction of toxic nitroaromatics to valuable amines is crucial for wastewater resource recovery, yet conventional catalysts suffer from active-site agglomeration and inadequate electronic modulation. Here, a sandwich-structured HNT@Au–CeCo nanoreactor was designed via interfacial confinement and bimetallic oxide synergy. Amino-functionalized halloysite nanotubes (HNTs) directionally anchored ultrafine Au nanoparticles, which were then coated in situ with an oxygen-vacancy-rich CeO2–Co3O4 shell. This catalyst achieved an apparent rate constant of 1.37 min–1 in reducing p-nitrophenol, representing superior improvement over the uncoated and single-oxide-coated counterparts. It also exhibited a low activation energy of 20.68 kJ mol–1 and a high turnover frequency of 825 h–1, outperforming most reported analogues. The catalyst demonstrated robust stability, broad substrate applicability in various nitroaromatics, excellent continuous-treatment capability, and effective retention of Au sites. Mechanistic studies revealed that the CeO2–Co3O4 heterojunction induced strong metal–support interaction and interfacial charge redistribution, accelerating electron transfer and the formation of active Au–H species at defect sites. DFT calculations identified the key reactive sites on the pollutant molecules during the reduction process. The ECOSAR assessment confirmed the efficient conversion of toxic nitroaromatics into low-toxicity products. This work provides an effective interfacial engineering strategy for designing high-performance nanocatalysts for environmental remediation.