Two-Dimensional Submonolayer Pt Clusters with Optimal Pt⁰-Pt^δ+ Sites for Efficient Methylcyclohexane Dehydrogenation.

Abstract

Methylcyclohexane dehydrogenation (MCHDH) is vital in hydrogen storage and carriage technologies. However, Pt/Al₂O₃, as a classic practical catalyst for MCHDH, remains ambiguous regarding the catalytic structure of active Pt sites for C-H activation at the atomic scale due to a shortage of subnanometer characterization. Here, based on comprehensive structural characterizations and density functional theory (DFT) calculations, we demonstrate optimal active Pt sites: two-dimensional (2D) submonolayer clusters (SLCs) interfaced with γ-Al₂O₃ with an appropriate ratio of Pt^δ+ to Pt⁰ to form optimal Pt⁰-Pt^δ+ interfacial sites that have superior activity for the MCHDH reaction. This SLC's catalyst achieves a reaction rate of up to 29,353 mmol g_Pt^-1 min^-1 at 320 °C, with a 99.98% selectivity for toluene over MCHDH, which is significantly better than that of the corresponding Pt single atoms and conventional Pt nanoparticles (NPs) catalysts. The excellent MCHDH performance of Pt 2D SLCs is attributed to their sufficient 5d-electron domination and the optimal Pt⁰-Pt^δ+ sites, which facilitate the sequential activation of multiple C-H bonds and toluene desorption. In comparison, the presence of too many continuous Pt⁰-Pt⁰ sites in Pt 2D SLCs can hinder these processes. Our study highlights that constructing atomic-scale 2D submonolayer metal clusters is a promising strategy for optimizing efficient catalysts with abundant M⁰-M^δ+ (M = metal) sites, enhancing the catalytic performance for selective C-H bond activation.