Natural halloysite nanotubes enclosing PdAg alloy nanoparticles as nanoreactors with enhanced catalytic performance

Hollow nanoreactors, with their void-confinement effects and stable carrier properties, hold great promise for catalytic applications. In this study, we present a green and versatile method to confine PdAg alloy nanoparticles (NPs) within halloysite nanotubes (HNTs), creating highly efficient catalysts (Pd_xAg_y@HNTs-OH) for the reduction of toxic pollutants like 4-nitrophenol (4-NP), Methyl Orange (MO), and Congo Red (CR). PdAg NPs are selectively anchored to the inner surface of HNTs, with the exclusively lumen-confined PdAg₃@HNTs-OH exhibiting superior activity compared to dual-surface-loaded counterparts (d-PdAg₃@HNTs), directly evidencing the critical role of void confinement. Experimental and density functional theory (DFT) studies reveal that HNTs modulate the electronic structure of PdAg NPs, reducing energy barriers for 4-NP adsorption and intermediate conversion. This electronic optimization, combined with spatial confinement, ensures exceptional catalytic performance. The work establishes a dual engineering strategy that integrates electronic regulation with nanoscale spatial control to design high-performance catalytic nanoreactors.