The synthesis of randomly alloyed palladium-silver nanoparticles for the catalytic treatment of aqueous nitrite

Nitrate (NO₃-), and its daughter compound nitrite (NO₂-), are two of the most prevalent contaminants in drinking water. Catalytic degradation of NO₃- and NO₂- provides a treatment method with a small environmental footprint, though it is currently hindered by the need for a catalytic system that pairs reduced costs with enhanced activity and longevity. Monodisperse, randomly-alloyed palladium–silver nanoparticles (Pd [subscript X] Ag [subscript 100-X] NPs) with tunable compositions (X = 50–95) were studied for use as catalysts in aqueous NO₂- reduction. The synthesized Pd [subscript X] Ag [subscript 100-X] NPs were supported on amorphous silica (SiO₂) and studied for use as aqueous NO₂- reduction catalysts in batch reactors with H₂ gas as the electron donor. Nitrite reduction followed pseudo-first-order reaction kinetics for ≥80% conversion, and displayed a high selectivity (>98%) for nitrogen gas (N₂) as the end product. Nearly all compositions displayed increased activity over pure PdNPs supported on amorphous SiO₂. Catalyst longevity was assessed for the most active catalyst. Throughout recycling, the catalytic activity decreased, although complementary analysis indicated no major physical changes of the catalyst. Overall, this work demonstrates that incorporating inexpensive, semi-noble metals into bimetallic alloys is a potential avenue for increasing catalytic activity while decreasing catalyst cost for NO₂- reduction