Reduced Carbon Monoxide Saturation Coverage on Vicinal Palladium Surfaces: the Importance of the Adsorption Site.

Fernando Garcia-Martinez,Stefano Albertin,J Enrique Ortega,Frederik Schiller,Sabrina M Gericke,Dorotea Gajdek,Henrik Grönbeck,Lindsay R Merte,Johan Zetterberg,Edvin Lundgren,Elisabeth Dietze

doi:10.1021/acs.jpclett.1c02639

Abstract

Steps at metal surfaces may influence energetics and kinetics of catalytic reactions in unexpected ways. Here, we report a significant reduction of the CO saturation coverage in Pd vicinal surfaces, which in turn is relevant for the light-off of the CO oxidation reaction. The study is based on a systematic investigation of CO adsorption on vicinal Pd(111) surfaces making use of a curved Pd crystal. A combined X-ray Photoelectron Spectroscopy and DFT analysis allows us to demonstrate that an entire row of atomic sites under Pd steps remains free of CO upon saturation at 300 K, leading to a step-density-dependent reduction of CO coverage that correlates with the observed decrease of the light-off temperature during CO oxidation in vicinal Pd surfaces.

Highlights

Steps at metal surfaces may influence energetics and kinetics of catalytic reactions in unexpected ways
Spectroscopy and Density Functional Theory (DFT) analysis allows us to demonstrate that an entire row of atomic sites under Pd steps remains free of Carbon monoxide (CO) upon saturation at 300 K, leading to a step-densitydependent reduction of CO coverage that correlates with the observed decrease of the light-off temperature during CO oxidation in vicinal Pd surfaces
Low temperature activity can be achieved by use of catalysts where the CO desorption energy is lowered, such as some bimetallic alloys,[5] or bifunctional surfaces, such as oxide-supported nanoparticles, where CO and O2 adsorption occurs at physically separated nanoparticle and oxide sites.[6,7]