(15h) Tailoring the Electronic Structure of Metal Cationic Centers in Non-Stoichiometric Mixed Metal Oxides for Enhanced Electrochemical Performance

Tuning the electrocatalytic properties of materials by tailoring the electronic structure of their active centers is critical for the rational design of heterogeneous electrocatalysts.^1,2 This is, however, often challenged by the multisite reactivity of catalysts inducing barriers to controlled manipulation of the active sites. Non-stoichiometric mixed metal oxides present promising systems toward implementation of such approach since ligand and charge transfer modes can be used systematically to modify the reactivity of the metal cationic centers within these oxide frameworks.^1–3 In this presentation, we show how the compositional versatility of ABO₃ perovskites (A and B are rare-earth/alkaline-earth and transition metal cations, respectively) can be utilized as a lever to tune the electronic structure of dispersed 4d/5d transition metal cationic centers within the oxide framework pushing their electrochemical activity for oxygen reduction reaction (ORR) beyond that of conventional 3d transition metal-based perovskites.⁴ We find that in general, the electrocatalytic activity of dispersed 4d/5d cationic centers in perovskites can be tuned by tailoring of their electronic structure via variations in the oxophilicity of 3d and 4d/5d metal cations within the perovskite framework. This is demonstrated through the example of highly dispersed Rh cations in LaNi_1-xRh_xO₃, x≤0.01 perovskites, which leads to the optimal charge transfer from cationic Rh sites to the adjacent lattice oxygens making these Rh catalytic centers more active than those in LaRhO₃ or supported Rh-based electrocatalysts. These findings present avenues for tailoring the electronic structure of cationic sites in non-stochiometric mixed metal oxides as approaches for enhancing their electrocatalytic activity.

References:

(1) Kitchin, J.R., et al., J. Chem. Phys. 2004, 120, 10240–10246.

(2) Wang, X., et al., Chem. – Eur. J. 2017, 23, 1093−1100.

(3) Gu, X.K., et al., J. Catal. 2020, 388, 130−140.

(4) Samira, S., et al., ACS Energy Lett. 2021, 6, 1065−1072.