Polydopamine Nanotubes Decorated with Ag Nanoparticles as Catalyst for the Reduction of Methylene Blue

In the present work, polydopamine nanotubes (PDA NTs) decorated with silver (Ag) nanoparticles (NPs) were successfully fabricated via a template induced self-polymerization of dopamine, followed by in situ reduction and immobilization of NPs from nitrate solution. The typical Ag@PDA NTs exhibits 39.1 wt % of Ag content and excellent catalytic activity as demonstrated by the reduction of a model organic pollutant, methylene blue, with an apparent rate constant of 3.19 min–1 in the first-order kinetics model, which is the highest value reported so far. The superior catalytic performance is attributed to the high Ag loading, uniform distribution of NPs, and excellent dispersity in water. Moreover, it is believed that the superhydrophilic hollow morphology of PDA NTs with ultrahigh porosity (81.4%) and open ends facilitates the contact of the catalysts with reactant molecules and mass transfer in aqueous reaction. The Ag@PDA NTs nanocatalysts could be easily recycled, and the catalytic efficiency remained nearly unchanged over 10 cycles. This synthetic strategy was proved to be applicable to other typical metal catalysts (e.g., Pt, Pd, Au). This work presents a universal approach to fabricate highly efficient nanocatalysts with PDA NTs as supports used for the reduction and degradation of organic dyes.