Preferential Oxidation of Carbon Monoxide in Hydrogen-Rich Streams over CuO/CeO2 Catalysts: How Nano (and Subnano) Structure Affects Catalytic Activity and Selectivity

Preferential oxidation of carbon monoxide in hydrogen-rich streams needs a suitable catalyst that selectively oxidizes CO avoiding H2 oxidation. Among the proposed catalysts, copper oxide supported on ceria (CuO/CeO2) received wide interest due to its intrinsic activity and selectivity and low cost with respect to noble metals. In particular, it has been shown that the performances are significantly affected by optimizing the copper-ceria interaction, and then the copper dispersion. In this light, reducing to nanoscale levels has been proven to be the solution. In this chapter, results of the effect of nano and subnano structures of CuO/CeO2 catalysts on the CO-PROX performance are reviewed and critically discussed. At nanosize, Cu dispersion and oxygen mobility are both enhanced. Furthermore, the copper reduction to the metallic Cu (H2 oxidation sites) is limited and CO2 desorption is activated at lower temperatures. The role of dopants and/or supports as graphene and carbon nanotubes in improving the intrinsic activity and the resistance to the inhibiting effect of carbon dioxide and water vapor are also discussed, highlighting the effect of dopants on the modification of the redox properties by increasing bulk and/or surface oxygen vacancies.