Ab imetallic Cu/Cu 51 Zr 14 precatalyst,a ctivated in situ, for hydrogen generation from methanol and water providesv ery high CO 2 selectivity (> 99.9 %) and high H 2 yields. Referenced to the geometrics urface area of our model surface, highera ctivity of at least one order of magnitude was observed in comparison to supportedC u/ZrO 2 and Cu/ZnO/ZrO 2 catalysts. Evolution of structurala ctivation monitored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microscopy indicatest ransformation of the bimetallic Cu/Cu 51 Zr 14 precatalyst into an active, selective, and self-stabilizing state with coexistence of dispersed Cu and partially hydroxylated tetragonal ZrO 2 .The outstanding performance is assigned to the presence of ah igh interface-site concentration following in situ decompositiono ft he intermetallic compound. These actives ites result from the cooperation of Cu, responsible for methanol activation,a nd tetragonal ZrO 2 ,w hich activates the water by surface hydroxylation.Copper-based catalysts are widely used for technical applications in methanolc hemistry,w ell-known examples include methanol synthesis from syngasw ith an optimized CO/CO 2 ratio, hydrogenation/photoreduction of CO 2 to produce "renewable" methanol, and methanol steam reforming (MSR) as the reversal of the synthesis reactionf rom CO 2.[1] The ability to control product selectivity is ak ey criterion for technical usage. Therefore, to realize the efficient on-boardp roduction of clean hydrogen in, for example, automotive applications, the key targets for MSR are high CO 2 selectivity,l ow CO content,a nd maximum H 2 yield in the reformate.[2] With respect to the catalytic functiono fZ rO 2 in MSR, the simple addition of ZrO 2 to the conventionally used Cu/ZnO catalysts overcomes the inherent drawback of purely ZnO-based catalysts,t hat is, the poor sinterings tability.[2] Beneficial synergistic effectsf or methanol synthesis have also been described for Cu/Zn and the ternary Cu/Zn/Al system prepared by ac o-precipitation technique.[3]Synergistic Cu-ZrO 2 interactions have also been reported for Cu/ZrO 2 catalysts without ZnO, involving CuÀOÀZr bonds at the phase boundary. The Cu-ZrO 2 interactions are believed to play ac rucial role in steering the methanol reforming reaction to maximum CO 2 selectivity.[4] Specifically,ananocrystalline Cu/ tetragonal ZrO 2 catalyst synthesized by ap olymer templating technique [5] was reported to be more active, selective, and stable in MSR than the technical Cu/ZnO/Al 2 O 3 methanol synthesis catalyst.[6] Although the beneficial effects of the redox chemistry of Cu and the Cu 0 /Cu oxidized ratio at the interface has been suggesteda sa ni mportants electivity descriptor,a longside disorder and strain phenomena within the metallicC u phase, [2] ac ontradictingi nfluence hasa lso been reported. Both beneficial [4a, b] and adverse [4d] effectso ft he reducibility of Cu can be found in the literature. Nevertheless, any influence appears strongly connected to the quantity...