Performance Descriptor\nof Subsurface Metal-Promoted\nBoron Catalysts for Low-Temperature Propane Oxidative Dehydrogenation\nto Propylene

Boron-based catalysts have exhibited excellent olefin\nselectivity\nin the oxidative dehydrogenation of propane (ODHP) reaction. The substrate\nmaterial should be a potential platform for performance modulation\nof boron catalysts in this reaction since the introduction of subsurface\nNi promoters significantly improves the activity. In this study, we\ndeciphered the substrate effect and identified a performance descriptor\nto comprehend the roles of subsurface materials in BO<sub><i>x</i></sub>/metal/BN ODHP catalysts by evaluating different\nmetal promoters. Performance evaluation and transient infrared spectroscopic\nexperiments demonstrate that the intrinsic activity and kinetic behaviors\nof the O–H bond dissociation/regeneration on the metal-promoted\nBO<sub><i>x</i></sub> overlayer are metal substrate-dependent.\nCombining density functional theory (DFT) calculations, it is found\nthat the dissociation/regeneration inclination of the O–H bond\nin BO<sub><i>x</i></sub>(OH)<sub>3–<i>x</i></sub> active species is controlled by the affinity of H for boron\noxide species. The metal-O binding energy, which has been demonstrated\nto be linearly correlated with H affinity, can serve as a straightforward\nperformance descriptor for both low-temperature radical initialization\nand ODHP reaction, revealing this reaction is controlled by the Sabatier\nprinciple, and moderate metal-O binding energy is essential for achieving\nremarkable performance in the BO<sub><i>x</i></sub>/M/BN\ncatalysts. Following the guidance of a potential descriptor, Ni–Rh\nalloy substrates are investigated and the substrate with a Ni/Rh molar\nratio of 15:1 significantly enhances the low-temperature intrinsic\nactivity of the metal-modified BO<sub><i>x</i></sub> to\n9.26 μmol/(m<sup>2</sup>·s), which reaches 105.9 times\nthat of h-BN and is 18.3% larger than the monometallic BO<sub><i>x</i></sub>/Ni/BN catalysts.