Alloying provides a means by which to tune a metal catalyst's electronic structure and thus tailor its performance; however, mean-field behaviour in metals imposes limits. To access unprecedented catalytic behaviour, materials must exhibit emergent properties that are not simply interpolations of the constituent components' properties. Here we show an emergent electronic structure in single-atom alloys, whereby weak wavefunction mixing between minority and majority elements results in a free-atom-like electronic structure on the minority element. This unusual electronic structure alters the minority element's adsorption properties such that the bonding with adsorbates resembles the bonding in molecular metal complexes. We demonstrate this phenomenon with AgCu alloys, dilute in Cu, where the Cu d states are nearly unperturbed from their free-atom state. In situ electron spectroscopy demonstrates that this unusual electronic structure persists in reaction conditions and exhibits a 0.1 eV smaller activation barrier than bulk Cu in methanol reforming. Theory predicts that several other dilute alloys exhibit this phenomenon, which offers a design approach that may lead to alloys with unprecedented catalytic properties.

The active sites of Cu/ZnO‐based catalysts, commercially applied for the hydrogenation of CO2 or CO2‐rich synthesis gas, are still subject of current debates. Generally, the discussion is focused on the nature of the interfacial contact between Cu and ZnO, particularly whether it is rather of oxidic (Cu−ZnO) or alloying (Cu−Zn) character. We report on kinetic investigations on a Cu/ZnO : Al high performance catalyst activated at different temperatures. Incrementally increasing temperature under reductive conditions leads also to increased CuZn‐alloy formation, analyzed by in‐situ X‐ray diffraction, in‐situ X‐ray absorption spectroscopy and high resolution transmission electron microscopy. The combination of the catalytic data and the complementary characterization techniques provide valuable insights on the relevant reaction sites for CH3OH formation. Our results highlight the complexity of the interfacial contact with evidence for Cu−ZnO reaction sites and clarify the negative impact of CuZn alloy formation on the nature of the active site.

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The existence of a limited solid-solution series in the Cu/Zn binary metal oxalate system is reported. Coprecipitation was applied for the preparation of a comprehensive set of mixed Cu/Zn oxalates. Rietveld refinement of the XRD data revealed the formation of mixed-metal oxalate single phases at the compositional peripheries. Accordingly, the isomorphous substitution of Zn into Cu oxalate takes place at Zn contents of ≤6.6 and ≥79.1 atom %. Zn incorporation leads to a pronounced unit-cell contraction accompanied by Vegard-type trends for the lattice parameters. Morphologically, both solid solutions show close resemblance to the corresponding pure single-metal oxalates, and thus distinct differences are identified (SEM). The successful formation of solid solutions was further evidenced by thermal analysis. The decomposition temperature of the oxalate was taken as an approximation for Zn incorporation into the Cu oxalate structure. Single decomposition events are observed within the stated compositional boundaries and shift to higher temperature with increasing Zn content, whereas multiple events are present near Cu/Zn parity. Moreover, these findings are supported by IR and Raman spectroscopic investigations. This study on the Cu/Zn mixed-metal oxalate system sheds light on the important prerequisites for solid-solution formation and identifies the structural limitations that predefine its application as catalyst precursor.

A single-step rapid hydrothermal low-temperature process for the formation of high purity polycrystalline Agbased delafossite oxides 3R-AgBO 2 (B: Al, Ga, In) is reported. For the synthesis process reusable and widely available PTFE-lined pressure vessels are used. The presence of an elemental Ag byphase is traced back to the metastability of the Ag-delafossite under the reaction conditions. High-purity products were obtained by decreasing the synthesis time requirements by up to 90 %. The effect of the isoelectronic B-site atoms on the structure and bonding situation were comparatively studied experimentally and by ab-initio calculations. Distorted coordination [a]