PdCu Alloy Catalyst for Inhibition-free, Low-temperature CO Oxidation

Designing robust catalysts for low-temperature oxidation is pertinent to the development of advanced combustion engines to meet increasingly stringent emissions limitations. Oxidation of CO, hydrocarbon, and NO pollutants over platinum-group catalysts suffer from strong inhibition due to their competitive adsorption, while coinage metals are generally slow at activating O2. Through computational screening, we discovered a PdCu alloy catalyst that completely oxidizes CO below 150 degrees C without inhibition by NO, propylene or water. This is attributed primarily to geometric effects and the presence of CO bound to Pd sites within the Cu-rich surface of the PdCu alloy. We demonstrate that the novel PdCu catalyst can be used in tandem with a PtPd catalyst to achieve sequential, inhibition-free, complete oxidation of CO in a two-bed system, while also achieving 50 % NO conversion below 120 degrees C. Moreover, neither water nor propylene adversely affect the low temperature CO oxidation activity. In contrast to typical PdPt alloys used in diesel oxidation catalysis, the rate of CO oxidation on a computationally identified PdCu alloy catalyst does not slow down when NO is present. To get the best of both worlds, a dual-bed configuration of PdCu for the oxidation of CO at low temperature, followed by PdPt to oxidize NO and hydrocarbons does the trick while using 50 % less platinum.image