Tuning activity of Pt/FeOx/TiO2 catalysts synthesized through selective-electrostatic adsorption for hydrogen purification by prox reaction

Hydrogen purification by removing CO traces was studied via the preferential CO oxidation (PROX) reaction using highly dispersed Pt catalysts supported on dual oxide FeO x /TiO 2 . These catalysts were prepared by the strong electrostatic adsorption (SEA) method by varying the pH of synthesis and the calcination temperature. By measuring the point of zero charge (PZC) of the support components, it was possible to determine the pH in which Pt can be selectively deposited onto one of the support components, obtaining Pt dispersion values above 90%. The selective SEA of a Pt precursor onto the co-support (FeO x ) was achieved at a synthesis pH between the PZCs of the support components (i.e., TiO 2 PZC = 5.2 and Fe 2 O 3 PZC = 6.9) by using a Pt anionic complex. The catalytic activity for the PROX reaction, expressed in terms of the CO conversion, O 2 selectivity to CO 2 , apparent activation energy, and turnover frequency, confirmed that the SEA prepared catalysts were active and selective for the PROX reaction. XPS and TPR results of the Pt/FeO x /TiO 2 catalysts showed the formation of Pt-FeO x interfaces, called as (Pt-FeO x ) i interfacial sites, which enhanced the stability and catalytic activity for the PROX reaction. The concentration of these sites can be controlled by the synthesis conditions used, mainly pH and to a lower extent the calcination temperature. • Pt/FeO x /TiO 2 catalysts were prepared by SEA at a pH that ensures a Pt selective deposition onto Fe-based support. • 1 nm Pt crystallites were selectively deposited over FeO x at a pH between the PZCs of the support components. • The formation of (Pt-FeO x ) i interfacial sites were detected by XPS, TPR, TEM and operando DRIFTS analyses. • The concentration of (Pt-FeO x ) i interfacial sites is affected by the calcination temperature and the synthesis pH. • The concentration of (Pt-FeO x ) i interfacial sites was correlated with the activity of Pt–Fe catalysts in the PROX reaction.