Free-Atom-Like d States Beyond the Dilute Limit of Single-Atom Alloys

Abstract

Through a data-mining and high-throughput density functional theory approach, we identify a diverse range of metallic compounds that are predicted to have transition metals with “free-atom-like” d states that are highly localized in energy space. Design principles that can favor the formation of localized d states are uncovered, among which we note that site isolation is often necessary but that the dilute limit, as in most single-atom alloys, is not a pre-requisite. Additionally, the majority of localized d state transition metals identified from the computational screening study exhibit partial anionic character due to charge transfer from neighboring metal species. Using CO as a representative probe molecule, we show that localized d states for Rh, Ir, Pd, and Pt tend to reduce the binding strength of CO compared to their pure elemental analogues, whereas this does not occur as consistently for the Cu binding sites. These trends are rationalized through the d-band model, which suggests that the significantly reduced d-band width results in an increased orthogonalization energy penalty upon CO chemisorption. With the multitude of inorganic solids that are predicted to have highly localized d states, the results of the screening study may lead to new avenues for heterogeneous catalyst design from an electronic structure perspective.

Enhanced Catalytic Activity of Bimetallic Ordered Catalysts for Nitrogen Reduction Reaction by Perturbation of Scaling Relations

“…Those adsorption configurations break the valency rule and increase the adsorption energy by forming additional antibonding states through the covalent effect (Figure c), which is hard to capture using the electronic descriptors mentioned above. In general, increasing ε d and decreasing ε w correspond to increasing the hybridization contribution and the repulsion contribution, respectively . The smaller split between bonding and antibonding states in Cu 3 Ta compared to that on Ta 3 Cu may suggest a slight repulsion contribution because of the decreasing ε w on the single-atom-like Ta on Cu 3 Ta.…”