Elucidating the O2 reduction reaction on 2D monolayer LaMnO3 perovskite

Abstract

The O₂ reduction reaction (ORR) is critical in energy conversion technologies such as proton exchange membrane fuel cells (PEMFCs) and metal-air batteries (MABs), and it is a fundamental reaction related to various disciplines such as energy conversion, material dissolution and renewable green energy technology. Despite extensive research, efficient and cost-effective catalysts remain a great challenge for scientists. Platinum-based catalysts, while effective, are prohibitively expensive and lack durability. In this work, a novel 2D monolayer LaMnO₃ perovskite was computationally modeled by cleaving a (001) plane from the 3D LaMnO₃ cubic perovskite. The 2D monolayer showed a high density of states along with overlapping energy bands at the Fermi level, indicating its potential for use as a cathode material. Detailed ORR pathways, including dissociative and associative reaction mechanisms, were explored on the surfaces of 2D monolayer LaMnO₃. For all the intermediates involved in the ORR, the changes in Gibbs free energy (ΔG) were calculated by employing the PBE-D method. The 2D monolayer LaMnO₃ demonstrated superior selectivity for the associative mechanism than for the dissociative mechanism, as described by the obtained free energy diagram or potential energy surface (PES) plot. Bader charge analysis confirmed a charge transfer of +0.6 |e| during the adsorption of O₂ on the surface of the 2D monolayer LaMnO₃ perovskite. The calculated value of the theoretical overpotential was found to be 1.01 V for 2D monolayer LaMnO₃. This theoretical/computational groundwork lays the foundation for future applications of 2D monolayer LaMnO₃ perovskite-based electrocatalysts, indicating their promise as Pt-free alternatives for fuel cell components.