Synergistic photothermal and bimetallic catalysis for enhanced reduction of 4-nitrophenol using a “core-shell-satellite” structured Fe3O4@PDA@Ag-Au nanocatalyst

This study designed and synthesized a Fe 3 O 4 @PDA@Ag-Au NPs nanocatalyst featuring a “core-shell-satellite” structure, aimed at efficiently reducing 4-nitrophenol through photothermal catalysis. Under 808 nm near-infrared laser irradiation, the material demonstrated exceptional photothermal performance and catalytic activity. The reduction rate of 4-nitrophenol reached 90.35 %, with a reaction rate constant of 0.1397 min −1 , significantly surpassing that of a water bath heating system at the same temperature. The high efficiency was attributed to two synergistic effects: the photothermal conversion facilitated by the polydopamine shell and the unique resonance effect exhibited by Ag-Au bimetals. This synergy elevated the system’s equilibrium temperature to 50.7 °C (12.8 °C higher than that of pure water) and generated active site pairs on the Ag-Au interface. These sites enhanced critical reaction steps, thereby reducing the activation energy to 13.8 kJ·mol −1 ,a reduction of 24.0 % compared to that observed in the water bath system (18.3 kJ·mol −1 ). This catalyst could be easily recovered using magnets and maintained over 90 % efficiency after seven cycles. By integrating photothermal catalysis, bimetallic synergy, and magnetic separation, this study presents a novel strategy for developing efficient and recyclable catalysts with significant potential for addressing nitroaromatic organic pollutants.