Preferential oxidation of carbon monoxide in hydrogen over supported Au based catalysts
Hydrogen is important feedstock for a number of industrially relevant processes, such as ammonia production, methanol synthesis and oil refining. Recently, hydrogen has attracted particular attention as a clean and efficient energy carrier that meets the growing demand in future fuel applications, e.g., hydrogen vehicles and household fuel cells (mostly proton exchange membrane fuel cells (PEMFC)). To date, majority of hydrogen is produced by steam methane reforming, followed by water-gas-shift reaction. However, the resulting H2-feeds still contain ~1% of CO, which should be removed for subsequent applications. For instance, even ppm level of CO is highly detrimental to PEMFC, since it can rapidly poison/deactivate the Pt catalysts in the electrodes.
Preferential oxidation of CO under H2-rich atmosphere, also known as CO-PROX, is undoubtedly the most promising method for CO removal. Gold is the choice of metal catalyst as it can oxidize CO to CO2 with high activity under the ambient operating conditions even at room temperature. However, H2 can also be partially oxidized to H2O during reaction, which consumes valuable H2 and thus reduces the overall efficiency/selectivity of CO-PROX. As a consequence, the catalysts that achieve the 50/50 goal, i.e., 50 ppm outlet CO concentration with 50% O2-to-CO2 selectivity, are still scarce. Therefore, development of CO-PROX catalysts that oxidize CO with high activity/selectivity with minimal consumption of H2 is highly required.
Here we aim at i) development of Au based catalysts that achieve beyond 50/50 goal, ii) understanding the underlying CO-PROX mechanisms, and thus iii) providing new insights for the rational design of efficient CO-PROX catalysts.