Plasma-enabled synthesis of Pd/GO rich in oxygen-containing groups and defects for highly efficient 4-nitrophenol reduction

Effective catalytic removal of 4-nitrophenol (4-NP) in industrial wastewater remains a significant challenge due to the lack of highly efficient and stable catalysts. Herein, we demonstrated a promising plasma method for the facile, ultra-fast and low-temperature synthesis of graphite oxide (GO)-supported palladium catalyst (Pd/GO-P) rich in oxygen-containing groups (OCGs) and defects with smaller Pd nanoparticles (NPs) for highly efficient 4-NP reduction. The plasma method limited the damage to the OCGs and retained more OCGs (mainly alkoxy and hydroxyl groups) on the GO surface. In addition, plasma treatment can increase the active sites and the density of GO surface defects. These OCGs and defects promoted the 4-NP adsorption and improved the catalyst dispersion in the aqueous solution of 4-NP, thereby enhancing the catalytic reduction performance. The Pd/GO-P catalyst showed the highest reduction of 4-NP reported thus far, with a concentration-normalized rate constant of 5576 min−1 g−1 L. This value was 51.6 and 20.5 times greater than that using Pd/rGO-H prepared by a traditional thermal reduction method and a commercial Pd/AC catalyst, respectively. This work opens the avenue of exploring the use of plasma for the rational design of supported Pd catalysts with superior performance for the reduction and recycling of 4-NP in wastewater.