Maximizing the Pt-CuOx interface by trace Cu boosts CO preferential oxidation

Preferential oxidation of CO (CO-PROX) in H-2-rich streams is highly important for purifying the industrial grade H-2 used in proton-exchange-membrane fuel cells (PEMFC), but it is still limited to a relatively narrow operation temperature window. In this study, the trace amounts of Cu are used to modify a Pt/Al2O3 catalyst. The introduced Cu2+ species are atomically anchored on Pt nanoparticles through strong electrostatic adsorption. The prepared Pt-Cu/Al2O3 catalyst with 0.011 wt% Cu loading achieves complete CO oxidation between 138 and 215 degrees C, while the maximum CO conversion of Pt/Al2O3 is only 94%. The characterization showed that the formation of the Pt-CuOx interface not only produced additional active sites for O-2 activation but also weakened the adsorption strength of CO due to Pt existing in an electron-deficient state. The synergy at the interface of Pt-CuOx inhibits the competitive adsorption of CO and O-2 on Pt nanoparticles. Compared with CO oxidation, the presence of H-2 in CO-PROX promotes CO oxidation through the formation of a formate (HCOO-) intermediate. The addition of Cu accelerates the HCOO- intermediate oxidation over Pt-Cu/Al2O3. The strategy of constructing metal-oxide interfacial sites sheds light on designing better catalysts for the CO-PROX reaction.