High Performance Au–Pd Supported on 3D Hybrid Strontium-Substituted Lanthanum Manganite Perovskite Catalyst for Methane Combustion

Abstract

Bimetallic Au–Pd alloy nanoparticles (NPs) dispersed on nanohybrid three-dimensionally ordered macroporous (3DOM) La0.6Sr0.4MnO3 (LSMO) perovskite catalysts were fabricated via the l-lysine-mediated colloidal crystal-templating and reduction routes. The obtained AuPd/3DOM LSMO samples possess a nanovoid-like 3DOM construction with well-dispersed Au–Pd alloy NPs (2.05–2.35 nm in size) on the internal walls of the macropores. The Au–Pd alloy presence favored catalytic activity for methane combustion. The 3DOM LSMO support exhibits three key attributes: (i) a large surface area (32.0–33.8 m2/g) which aids high dispersion of the noble metal NPs on the support surface; (ii) abundant Brønsted acid sites which facilitate reactant adsorption and activation; and (iii) thermal stability. AuPd/3DOM LSMO has been synthesized with beneficial properties, including a richness of adsorbed oxygen species, increased oxidized noble metal species, low-temperature reducibility, and strong noble metal–3DOM LSMO interaction, all contributing to provide enhanced activity and a structure with high thermal and hydrothermal stability. In situ diffuse reflectance infrared Fourier transform spectroscopy studies revealed that including Au in the bimetallic system accelerated the reaction rate and altered the reaction pathway for methane oxidation by enriching the adsorbed oxygen species and decreasing the bonding strength between the reaction intermediates and the Pd atoms.