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The reactive metal-support interaction in the Cu-In 2 O 3 system and its implications on the CO 2 selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In 2 O 3 support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In 2 O 3 . This system already represents a highly CO 2 -selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H 2 formation rate of 1.3 µmol g Cu −1  s −1 . After reduction at 400 °C, the system enters an In 2 O 3 -supported intermetallic compound state with Cu 2 In as the majority phase. Cu 2 In exhibits markedly different self-activating properties at equally pronounced CO 2 selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol g Cu −1  s −1 has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst's constituents Cu and In 2 O 3 . In essence, the results also open up the pathway to in-depth development of potentially CO 2 -selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR.

Starting from subsurface Zr0-doped “inverse” Pd and bulk-intermetallic Pd0Zr0 model catalyst precursors, we investigated the dry reforming reaction of methane (DRM) using synchrotron-based near ambient pressure in-situ X-ray photoelectron spectroscopy (NAP-XPS), in-situ X-ray diffraction and catalytic testing in an ultrahigh-vacuum-compatible recirculating batch reactor cell. Both intermetallic precursors develop a Pd0–ZrO2 phase boundary under realistic DRM conditions, whereby the oxidative segregation of ZrO2 from bulk intermetallic PdxZry leads to a highly active composite layer of carbide-modified Pd0 metal nanoparticles in contact with tetragonal ZrO2. This active state exhibits reaction rates exceeding those of a conventional supported Pd–ZrO2 reference catalyst and its high activity is unambiguously linked to the fast conversion of the highly reactive carbidic/dissolved C-species inside Pd0 toward CO at the Pd/ZrO2 phase boundary, which serves the role of providing efficient CO2 activation sites. In contrast, the near-surface intermetallic precursor decomposes toward ZrO2 islands at the surface of a quasi-infinite Pd0 metal bulk. Strongly delayed Pd carbide accumulation and thus carbon resegregation under reaction conditions leads to a much less active interfacial ZrO2–Pd0 state.

To focus on the influence of the intermetallic compound—oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga 2 O 3 - and In 2 O 3 -supported GaPd 2 and InPd catalysts, respectively. To study the possible promoting effect of In 2 O 3 , an In 2 O 3 -doped Ga 2 O 3 -supported GaPd 2 catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga 2 O 3 support is strikingly different: rhombohedral and spinel-like Ga 2 O 3 phases, as well as hexagonal GaInO 3 and rhombohedral In 2 O 3 phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO 2 selectivity in MSR. Both Ga 2 O 3 and In 2 O 3 catalysts show a much higher activity, and in the case of GaPd 2 –Ga 2 O 3 , a much higher CO 2 selectivity. The promoting effect of In 2 O 3 is also directly detectable, as the CO 2 selectivity of the co-precipitated supported Ga 2 O 3 –In 2 O 3 catalyst is much higher and comparable to the purely In 2 O 3 -supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems. Graphical Abstract The presence of a variety of distinct supported intermetallic InPd and GaPd 2 particle phases is not detrimental to activity/selectivity in methanol steam reforming as long as the appropriate intermetallic phases are present and they exhibit optimized intermetallic-support phase boundary dimensions.

To identify the synergistic action of differently prepared Ni-ZrO2 phase boundaries in methane dry reforming, we compared an “inverse” near-surface intermetallic NiZr catalyst precursor with the respective bulk-intermetallic NixZry material and a supported Ni-ZrO2 catalyst. In all three cases, stable and high methane dry reforming activity with enhanced anticoking properties can be assigned to the presence of extended Ni-ZrO2 phase boundaries, which result from in situ activation of the intermetallic Ni-Zr model catalyst systems under DRM conditions. All three catalysts operate bifunctionally; methane is essentially decomposed to carbon at the metallic Ni0 surface sites, whereas CO2 reacts to CO at reduced Zr centers induced by a spillover of carbon to the phase boundaries. On pure bulk Ni0, dissolved carbon accumulates in surface-near regions, leading to a sufficiently supersaturated state for completely surface-blocking graphitic carbon segregation. In strong contrast, surface-ZrO2 modified bulk Ni0 exhibits virtually the best decoking and carbon conversion conditions due to the presence of highly dispersed ZrO2 islands with a particularly large contribution of interfacial Ni0-ZrO2 sites and short C-diffusion pathways to the latter.

To focus on the influence of the intermetallic compound-oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga.sub.2O.sub.3- and In.sub.2O.sub.3-supported GaPd.sub.2 and InPd catalysts, respectively. To study the possible promoting effect of In.sub.2O.sub.3, an In.sub.2O.sub.3-doped Ga.sub.2O.sub.3-supported GaPd.sub.2 catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga.sub.2O.sub.3 support is strikingly different: rhombohedral and spinel-like Ga.sub.2O.sub.3 phases, as well as hexagonal GaInO.sub.3 and rhombohedral In.sub.2O.sub.3 phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO.sub.2 selectivity in MSR. Both Ga.sub.2O.sub.3 and In.sub.2O.sub.3 catalysts show a much higher activity, and in the case of GaPd.sub.2-Ga.sub.2O.sub.3, a much higher CO.sub.2 selectivity. The promoting effect of In.sub.2O.sub.3 is also directly detectable, as the CO.sub.2 selectivity of the co-precipitated supported Ga.sub.2O.sub.3-In.sub.2O.sub.3 catalyst is much higher and comparable to the purely In.sub.2O.sub.3-supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems.

To focus on the influence of the intermetallic compound-oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga O - and In O -supported GaPd and InPd catalysts, respectively. To study the possible promoting effect of In O , an In O -doped Ga O -supported GaPd catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga O support is strikingly different: rhombohedral and spinel-like Ga O phases, as well as hexagonal GaInO and rhombohedral In O phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO selectivity in MSR. Both Ga O and In O catalysts show a much higher activity, and in the case of GaPd -Ga O , a much higher CO selectivity. The promoting effect of In O is also directly detectable, as the CO selectivity of the co-precipitated supported Ga O -In O catalyst is much higher and comparable to the purely In O -supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems. The presence of a variety of distinct supported intermetallic InPd and GaPd particle phases is not detrimental to activity/selectivity in methanol steam reforming as long as the appropriate intermetallic phases are present and they exhibit optimized intermetallic-support phase boundary dimensions.

To identify the synergistic action of differently prepared Ni-ZrO[sub.2] phase boundaries in methane dry reforming, we compared an “inverse” near-surface intermetallic NiZr catalyst precursor with the respective bulk-intermetallic Ni[sub.x]Zr[sub.y] material and a supported Ni-ZrO[sub.2] catalyst. In all three cases, stable and high methane dry reforming activity with enhanced anticoking properties can be assigned to the presence of extended Ni-ZrO[sub.2] phase boundaries, which result from in situ activation of the intermetallic Ni-Zr model catalyst systems under DRM conditions. All three catalysts operate bifunctionally; methane is essentially decomposed to carbon at the metallic Ni[sup.0] surface sites, whereas CO[sub.2] reacts to CO at reduced Zr centers induced by a spillover of carbon to the phase boundaries. On pure bulk Ni[sup.0], dissolved carbon accumulates in surface-near regions, leading to a sufficiently supersaturated state for completely surface-blocking graphitic carbon segregation. In strong contrast, surface-ZrO[sub.2] modified bulk Ni[sup.0] exhibits virtually the best decoking and carbon conversion conditions due to the presence of highly dispersed ZrO[sub.2] islands with a particularly large contribution of interfacial Ni[sup.0]-ZrO[sub.2] sites and short C-diffusion pathways to the latter.

The reactive metal-support interaction in the Cu-In O system and its implications on the CO selectivity in methanol steam reforming (MSR) have been assessed using nanosized Cu particles on a powdered cubic In O support. Reduction in hydrogen at 300 °C resulted in the formation of metallic Cu particles on In O . This system already represents a highly CO -selective MSR catalyst with ~93% selectivity, but only 56% methanol conversion and a maximum H formation rate of 1.3 µmol g  s . After reduction at 400 °C, the system enters an In O -supported intermetallic compound state with Cu In as the majority phase. Cu In exhibits markedly different self-activating properties at equally pronounced CO selectivities between 92% and 94%. A methanol conversion improvement from roughly 64% to 84% accompanied by an increase in the maximum hydrogen formation rate from 1.8 to 3.8 µmol g  s has been observed from the first to the fourth consecutive runs. The presented results directly show the prospective properties of a new class of Cu-based intermetallic materials, beneficially combining the MSR properties of the catalyst's constituents Cu and In O . In essence, the results also open up the pathway to in-depth development of potentially CO -selective bulk intermetallic Cu-In compounds with well-defined stoichiometry in MSR.