Tuning of the copper–zirconia phase boundary for selectivity control of methanol conversion

Abstract Chemical-vapor deposition (CVD) of a Zr(O-tBu) 4 precursor on different Cu substrates was used to prepare model systems for ZrO x H y –Cu catalysts and to test their reactivity and selectivity in methanol steam reforming (MSR). A partially hydroxylated and initially fully oxidized submonolayer ZrO x H y surface species results, exhibiting a pronounced catalytic synergism between the ZrO x H y overlayer and Cu only with respect to partial methanol dehydrogenation to formaldehyde. Thus, it differs strongly from in situ grown ZrO x H y layers on Cu formed from an initially bimetallic mixed Zr/ZrO x state under MSR conditions. CVD-grown Zr–OH groups are not stable under MSR conditions; thus reversible in situ hydroxylation and water-activating reaction channels are suppressed. Comparison of the two model systems indicates that only a dedicated Cu–ZrO x H y interface with in situ formed and reversibly hydroxylated sites (accessible only from initially (inter)metallic Cu/Zr species at the surface) leads to water activation, total oxidation of intermediate formaldehyde, and enhanced CO 2 selectivity.