Catalytic transformation of 4-nitrophenol into 4-aminophenol over ZnO nanowire array-decorated Cu nanoparticles

To realize economical and effective removal of hazardous 4-nitrophenol from the environment, we developed an easily recyclable ZnO nanowire array decorated with Cu nanoparticles. Its salix argyracea-shaped structure not only provides a platform to achieve stable and good dispersion of Cu nanoparticles, but also offers a great deal of catalytically active sites. The density functional theory calculations reveal that ZnO and Cu have a very beneficial synergistic effect on their catalytic capability. This synergy is ascribed to the electronic localization occurring at ZnO/Cu interface, which helps improve Cu nanoparticle's ability to adsorb electro-negatively 4-nitrophenolate ions and to capture hydrogen radicals, thereby accelerating the hydrogen transfer from metal hydride complex to 4-nitrophenol. Benefiting from these characteristics, it exhibits high efficiency and reusability towards the catalytic reduction of waste 4-nitrophenol to valuable 4-aminophenol with a rate constant of 43.02 × 10⁻³ s⁻¹ and an average conversion of 96.5% in 90 s during 10 cycles. This activity is superior to that of most reported noble- or non-noble-metal powder, bulk, coating, and array catalysts, indicating its competitive advantages in cost and efficiency, as well as enticing application prospects.