Scalable synthesis of reusable Ag@NiO micro-nanosynergized composite for highly fast reduction of 4-nitrophenol

Metal/semiconductor composites are promising catalysts. In this work, the three-dimensional flowery Ag@NiO micro-nanocomposite catalyst for the highly fast reduction of 4-nitrophenol to 4-aminophenol was prepared by simple homogeneous precipitation method. Ag@NiO composites exhibit better catalytic performance than Ag and NiO in reducing 4-nitrophenol. The catalytic experiments showed that when the specific surface area of Ag@NiO was 20.61 m²/g, the complete conversion time of 4-nitrophenol to 4-aminophenol was the shortest, the reaction kinetic constant was 11.01 × 10⁻³ s⁻¹, and the turnover frequency was 166.67 × 10⁻⁵ mol·g⁻¹·s⁻¹. The catalytic activity of Ag@NiO was not significantly reduced after five consecutive cycles. Furthermore, the synergistic effect of Ag and NiO of the Ag@NiO composites was investigated in this work. Ag@NiO micro-nanomaterials have the potential for industrial application with simple preparation method, high catalytic efficiency, and easy recycling.