Mechanisms of aqueous bromate reduction activity enhancement with well-defined bimetallic palladium-based catalysts

Abstract

Catalytic reduction has been shown to remove bromate (BrO3−) in drinking water without waste stream formation, though most reported catalysts rely on palladium (Pd), a financially and environmentally expensive metal. Emerging efforts show Pd can be partially replaced with less expensive metals in nanoparticle (NP) alloys, with enhanced hydrogenation reactivity. However, it is unclear if novel NP alloys will enhance bromate reduction, and if so whether they can be intelligently designed based on underlying mechanisms of enhancement. Herein, we address this knowledge gap reporting that well-defined alloyed PdCu and PdAg nanoparticles deposited on carbon nanotubes achieve a 3.9-times improvement in catalytic activity versus monometallic Pd catalysts, which further translates to catalysts prepared using straight-forward impregnation methods. Density functional theory results indicate that improved hydrogenation rates are related to optimized BrO3− and H binding on PdM surfaces achieved by electronic effects in PdCu alloys and unique surface ensembles in PdAg alloys. Overall, these catalysts delineate a pathway for improved bromate removal activity at environmentally relevant concentrations.