Catalyst deactivation due to coke formation and metal sintering presents a major challenge in industrial ethane dehydrogenation. Our group has recently developed a two-dimensional Mo₂TiC₂ MXene-supported Pt nanolayer catalyst with atomic-scale thickness, exhibiting excellent stability (24 hours at 550 °C without deactivation), high turnover frequency (1.2 s⁻¹), and >95% selectivity to ethylene [1,2]. While prior studies have focused on intrinsic reaction kinetics, the impact of diffusion—particularly under high-temperature conditions and in confined pore environments—remains poorly understood. In this work, we present a systematic study on reaction-diffusion interactions within MXene-based catalysts. By tuning the interlayer spacing through metal ion treatments (e.g., Al³⁺, Mg²⁺, Na⁺), we achieved controlled pore sizes ranging from 3.2 to 7.2 nm. Catalytic testing reveals that larger pores correlate with higher reaction rates (~4.5×10⁻³ mol/kg_cat·s), while smaller pores exhibit reduced rates due to diffusion limitations. Pressure step-change experiments further show that elevated ethane pressures lead to transient rate increases followed by gradual declines, indicating accumulation of heavy hydrocarbon species that hinder diffusion and promote deactivation. The observed hysteresis in rate recovery upon pressure reduction underscores the significance of diffusional resistance from chemisorbed intermediates. Our analysis extends the conventional Weisz–Prater criterion by accounting for both reactant and product diffusivities at elevated temperatures, offering a more complete framework for evaluating diffusion effects in MXene-confined systems. This study highlights the critical role of pore size and operating pressure in governing the reaction-diffusion behavior of MXene-supported catalysts for ethane dehydrogenation. Our findings provide new insights into designing stable, high-performance catalysts for alkane upgrading, and establish a methodology applicable to other two-dimensional catalytic systems.
