Correlating Electronic Structure of Perovskites to their Activity towards Oxygen Electrocatalysis

Abstract

Developing activity descriptors for oxygen electrochemical reactions based on complex metal oxides paves the way to revolutionise catalysts for electrochemical energy storage and conversion devices, including metal-air batteries and regenerative fuel cells. Descriptors based on approximating binding strength between the targeted reactant and active site disregard the kinetic factors pertaining to reactions and the fact that the electrochemical process is involved in altering the Fermi energy level. The findings of the conducted investigation on the synthesised LaMnxNi1-xO3 highlight a new approach to the correlation between the electronic structures of active sites of metal oxide and electrochemical observations in operational conditions (e.g., applied potential and mass transport) to provide a general quantitative descriptor for electrochemical activity. This study also presents novel findings regarding identifying the pertinence to the element-projected density of states (p-DOS) that governs both reactions in which the phenomenological rate constants of OER and ORR are in a monotonic and second-order reaction relationship, respectively, to the relatively integrated element p-DOS for their associated Ni and Mn 3d orbitals. Moreover, the findings associated with the performed study on the synthesised La1-xCaxFeO3-δ system indicate an appreciable enhancement in the OER performance with the substitution of Ca over La, in which the OER catalytic activity is monotonically correlated with the density of identified Fe 3d states via the pseudocapacitive responses and the p-DOS. Conversely, the ORR kinetics demonstrates an independent behaviour as a function of Ca composition owing to the limited occupation of Fe 3d states in the energy scale of oxygen reduction.

Date of Award	10 Dec 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	David J Fermin (Supervisor) & Paul W May (Supervisor)