Supported palladium nanoparticles as highly efficient catalysts for radical production: Support-dependent synergistic effects

Abstract

Supported metallic palladium (Pd) acts as a real catalyst for peroxymonosulfate (PMS) activation to produce highly oxidizing species. However, the species produced are surface-bound in nature, and their use for pollutant degradation requires an inert supporting material to minimize the surface scavenging effect. In this study, we synthesized Pd nanoparticles (NPs) on different supporting materials (Al2O3, TiO2, SiO2, g-C3N4, C, and TiC), and compared their reactivity toward PMS activation for the first time. Experiments with 1,4-dioxane as a target pollutant showed that Pd/SiO2 had the highest reactivity of degrading 1,4-dioxane under acidic and neutral conditions, potentially due to the active interaction between SiO2 and PMS. However, Pd/Al2O3 had the greatest value of around 107% in the conversion of PMS to radicals. The ready oxidation of methanol to formaldehyde and degradation of 1,4-dioxane suggest that the activation of PMS by all the supported Pd NPs proceeded via a radical mechanism. These findings are critical to the development of efficient composite catalysts and the scientific understanding of observing different active species produced by Pd-catalyzed PMS.