Pulsed laser ablation-synthesized FePt nanoparticles have enhanced catalytic nitrite reduction activity

Abstract

Nitrate/nitrite pollution of water resources is an ubiquitous problem primarily due to the over application of fertilizer. While commercial methods which remove nitrates/nitrites exist, techniques which directly destroy the pollutants are more desirable. Nitrate/nitrite reduction by precious metal catalysts is one promising method to permanently convert nitrate/nitrite to non-toxic analogs. Amongst these, iron-platinum (“FePt”) compositions are generally considered inactive for NO₂^-. In this study, we demonstrate that bimetallic FePt catalysts synthesized via a pulsed-laser-ablation-in-liquid method (“PLAL-FePt NPs”) exhibit notably improved activity for NO₂^- compared to those synthesized by incipient wetness impregnation (“FePt/SiO₂”) with the same elemental composition. While FePt/SiO₂ catalyst (60 at% Pt) had nitrite reduction activity, the PLAL-FePt NPs (57 at%) were ∼8 times more active (k_cat ≈ 4.6 vs. 39.5 Lmin⁻¹g_{surface Pt}⁻¹) on a per surface Pt basis. When compared to the monometallic Pt catalyst, the PLAL-FePt NPs were ∼2 times more active. X-ray diffraction (XRD) show PLAL-FePt NPs to have intermetallic phases of Pt₃Fe₁ and Pt₁Fe₁. In contrast, FePt/SiO₂ have multiple phases (Pt, Pt₃Fe₁, Pt₁Fe₁, and Pt₁Fe₃). X-ray photoelectron spectroscopy (XPS) showed that Pt gained electron density from Fe, correlating to the increased nitrite reduction activity of both bimetallic materials. These findings indicate an earth-abundant element like iron can improve platinum catalysis, highlighting Fe-Pt intermetallic alloys for further study as hydrogenation catalysts.