Unveiling platinum's electronic and dispersion impacts for enhanced benzene combustion: From nanoparticles to nanoclusters and single atoms

Abstract

Catalytic combustion using platinum (Pt) supported on metal oxides emerges as an eco-friendly approach for benzene removal. However, relationships between Pt dispersion, adsorptive properties, and reactivity across overall Pt size regimes remain unclear, as many previous studies have focused on only one or two Pt size ranges. This study systematically examines the oxidation state, electron density, and resulting adsorptive properties of Pt across a range of sizes, including isolated atoms, sub-nanometer clusters, and nanoparticles. The as-synthesized Pt/Fe2O3 catalysts with defined Pt dispersion and electronic states on faceted Fe2O3 supports. Benzene combustion kinetics are measured over Pt entities from single atoms to sub-nanometer clusters and 2 nm particles, elucidating mechanisms and structure–reactivity links. Findings reveal surprising non-monotonic activity trends that deviate from dispersion features, with an order of: Pt sub-nanometer clusters < Pt single atoms < Pt nanoparticles. Despite high dispersion, single Pt atoms and nanoclusters exhibit lower benzene combustion activity than 2 nm Pt particles on Fe2O3. This reduced activity stems from diminished adsorptive affinity of single atoms and nanoclusters for benzene and O2, tracing back to their oxidized Pt valence states. In contrast, 2 nm Pt particles show excellent benzene and oxygen adsorption capacities enabled by metallic Pt ensembles, thus maximizing reactivity. Additional insights indicate single Pt atoms supported on Fe2O3 avoid competitive benzene/O2 adsorption through a non-competitive mechanism, moderately enhancing performance versus nanoclusters with competitive adsorption. However, Pt valence state has a greater impact than adsorption mechanisms, as Pt nanoparticles are considerably more active than single atoms and nanoclusters. In situ analysis proposes plausible benzene decomposition routes over active Pt sites. The novel findings that fine-tuning Pt dispersion and electronic structure—along with kinetic mechanisms—lead to significant variations in benzene combustion reactivity will assist rational design of efficient Pt catalysts for benzene elimination.