Ethane dehydrogenation on pristine and AlOx decorated Pt stepped surfaces

Abstract

Ethane dehydrogenation on pristine and AlO_x decorated Pt surfaces was studied using density functional theory (DFT) calculations and reaction kinetics experiments. Following the study of adsorption of fourteen distinct C₂H_x and CH_x species, the whole reaction network for ethane dehydrogenation on the terrace and the step of the pristine Pt(433) surface was systematically analyzed using DFT. We show that the under-coordinated step edge sites bind C₂H_x and CH_x species more strongly than terrace sites. These under-coordinated step sites facilitate deep dehydrogenation, resulting in accumulation of coke precursors on the surface and catalyst deactivation. We demonstrate that by decorating the step with AlO_x species the step edge sites can be blocked, leading to substantial suppression of deep dehydrogenation and coke formation. These findings were corroborated by reaction kinetics experiments where a four-fold enhancement of the turnover frequency for ethylene formation was measured on 10-cycle atomic layer deposited (ALD) alumina overcoated Pt/γ-Al₂O₃ catalyst compared to Pt/γ-Al₂O₃ without decoration with ALD-alumina. Our results suggest that AlO_x decorated Pt is a promising catalyst for alkane dehydrogenation and could have applications, including in endothermic cooling in hypersonic flights.