Janus-headed ZnPd – CO or CO2 from methanol
Methanol steam reforming (MSR, CH3OH + H2O à 3H2 + CO2) is considered as one of the most promising routes to produce high purity hydrogen for mobile fuel cell applications. However, the main drawback is the formation of CO as a byproduct, which has to be kept at a level of about 10 ppm to prevent poisoning of fuel cell catalysts.
MSR on single-phase samples of the intermetallic compound ZnPd, all possessing the CuAu type of crystal structure, proved that Pd-rich catalysts showed very low selectivity to CO2, while Zn-rich catalysts possessed CO2 selectivities up to 99.4%. In situ XPS studies revealed that only Zn-rich samples exhibited oxidized Zn species AND intermetallic ZnPd on the surface, thus making this combination very likely to be responsible for the excellent catalytic properties (M. Friedrich, D. Teschner, A. Knop-Gericke, M. Armbrüster, J. Catal. 285, 2012, 41–47; DOI: 10.1016/j.jcat.2011.09.013).