Comprehensive Mechanism and Microkinetic Model-Driven Rational Screening of 3N-Modulated Single-Atom Catalysts for Propane Dehydrogenation
Chunguang Dong, Zhuangzhuang Lai, Haifeng Wang
Abstract
Direct propane dehydrogenation (PDH) is an economically competitive and environmentally friendly industrial scheme used to produce propylene. Beyond the traditional Pt or Cr oxide catalyst, in this study, we focus on 3N-coordinated transition-metal single-atom catalysts confined within graphene (TM 1 -N 3 /C) for PDH due to their open coordination configuration with tunable capability for C–H activation. A total of 29 TM 1 -N 3 /C catalysts, covering the majority of 3d–5d transition metals, are systematically screened by first-principles mechanistic exploration and microkinetic modeling to assess their stability, activity, and selectivity; particularly, we considered the possible side reactions and the coverage effect of dominant intermediate for the realistic industrial application. Only six TM 1 -N 3 /C catalysts containing early TMs (TM = Sc, Ti, Y, Zr, La, Hf) are found to be stable at the working conditions of ∼900 K, owing to the unsaturation of the 3N-coordinated single-atom structure. A volcano-type activity trend is obtained with the adsorption energy of propylene being the key descriptor, which shows that TM 1 -N 3 /C generally exhibit higher activities than conventional catalysts. This is attributed to the openness of TM 1 -N 3 /C that makes the TM 1 intrinsically more active and the transition states or intermediates highly mobile (with larger than the expected entropy retained) at 900 K. Moreover, the side reactions and the coverage effect are also demonstrated to be prominent. After a thorough consideration of all of the influencing factors, we find that TM 1 -N 3 /C (TM = Ti, Zr, Hf) could be promising catalysts for practical applications with superior activities compared to the traditional Pt(111) catalyst. This study provides a comprehensive picture for the theoretical screening of TM 1 -N 3 /C for PDH and may pave the way for the use of low-coordination single-atom catalysts to enhance PDH in experiments.