Reactive Pt-TiN interfacial sites for H2O activation and the low-temperature water gas shift

Abstract

The reactive interfacial sites upon supported catalysts provide an alternative pathway to enable the reactants activation in an energetically favorable mode, thus decreasing the energy barrier and promoting the catalytic efficiency. By virtue of structural characterization, in-situ spectroscopic analysis, kinetic assessments and density functional theory (DFT) calculations, supported Pt/TiN catalysts are systematically studied to interrogate H2O activation on the Pt-TiN interfacial sites and its catalytic function during the low-temperature water gas shift (WGS). It is found that the partially oxygen-covered TiN surface is highly efficient for H2O activation by oxygen-assisted dissociation with an energy barrier of 0.41 eV, much less than that on metallic Pt surface. The formed hydroxyls binding on Ti sites, observed by in-situ X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD), could readily react with the adjacent CO adsorbed on Pt clusters with the reaction energy barrier of 0.43 eV to attain the individual catalytic cycle. Benefiting from the enhanced H2O activation, the catalytic turnover rate of CO-H2O reaction on Pt/TiN is 3.8 and 20.3 times higher than that on traditional Pt/TiO2 and Pt/SiO2 at 403 K, respectively. The interfacial reactive sites are the origin of low-temperature WGS on Pt/TiN catalysts.