The catalytic behavior of irregular copper aggregates in the reduction of 4-nitrophenol

Copper (Cu)-based materials attract considerable attentions to replace noble-metal based catalysts in the aqueous reduction of highly toxic 4-nitrophenol (4-NP). However, the reported catalysts generally owned well-defined shapes and structures that commonly rely on special synthesis condition. In contrast, the randomly dispersed and sintered Cu-based counterparts were neglected. Herein, irregular and coalesced Cu catalyst was fabricated and evaluated in 4-NP reduction. The as-synthesized CuBNC800 catalyst performed best among all the prepared materials, and the aggregated Cu nanoparticles was identified as the active centers. It showed that the pre-adsorption of 4-NP played positive role in the reaction. The reaction could be completed within 12 min at 25 °C over CuBNC800 without any treatment, while the elimination of the dissolved oxygen in solution significantly reduced the reaction time to only about 2 min. Moreover, full conversion of 4-NP was even realized within 30 min when the reaction temperature reduced to only 6 °C. Different from previously reported first order reaction kinetics over Cu-based catalysts, zero order reaction kinetics was recognized over CuBNC800 in this work, which could be attributed to the limited exposed active centers.