Tandem Catalysis for Enhanced CO Oxidation over the Bi-Au-SiO2 Interface

Bimetallic catalysts typically exploit unique synergetic effects between two metal species to achieve their catalytic effect. Understanding the mechanism of CO oxidation using hybrid heterogeneous catalysts is important for effective catalyst design and environmental protection. Herein, we report a Bi-Au/SiO2 tandem bimetallic catalyst for the oxidation of CO over the Au/SiO2 surface, which was monitored using near-ambient-pressure X-ray photoelectron spectroscopy. The Au-decorated SiO2 catalyst exhibited scarce activity in the CO oxidation reaction; however, the introduction of Bi to the Au/SiO2 system promoted the catalytic activity. The mechanism is thought to involve the dissociation O-2 molecules in the presence of Bi, which results in spillover of the O species to adjacent Au atoms, thereby forming Au & delta;+. Further CO adsorption, followed by thermal treatment, facilitated the oxidation of CO at the Au-Bi interface, resulting in a reversible reversion to the neutral Au valence state. Our work provides insight into the mechanism of CO oxidation on tandem surfaces and will facilitate the rational design of other Au-based catalysts.