Enhanced oxygen evolution reaction via the tunability of spin polarization and electronic states in a flexible van der Waals membranous catalyst

Abstract

The response of the magnetic field and strain engineering in an electrochemical process, such as the oxygen evolution reaction (OER), not only provides a strategy for enhancing catalytic performance through external fields and mechanical stress but also serves as a platform for revealing the functionality of multiple degrees of freedom in catalysts. The perovskite transition metal oxide (TMO) thin film with precise stoichiometry and lattice ordering enables atomic-level catalysis mechanisms in various electrochemical processes, thereby facilitating the design and engineering of promising catalysts. However, the perplexing dominance of spin in an OER process is still a puzzle due to the strong correlation between transition metal d and oxygen p orbitals. In this study, we utilized La_0.7Sr_0.3MnO₃ (LSMO) manganite as a ferromagnetic OER catalyst, which was directly deposited onto a flexible mica substrate. By subjecting LSMO to a tensile stress, we observed an enhanced OER, and the OER performance of LSMO improved by 30% with a +0.2% strain due to the weakened chemisorption of Mn–O. Moreover, it has been observed that the OER performance can be improved by approximately 87%, while the overpotential can be reduced by around 22% through the combination of a 5 kOe magnetic field and +0.2% strain. The OER performance of LSMO changed by ∼153% under 4% strain and 5 kOe magnetic field. Our experiments indicate that the primary source of the observed magnetic response is derived from the triplet state of O₂, in which spin-polarized d and oxygen p orbitals decrease the spin potential within OER. This study provides experimental evidence for understanding the spin degree and electronic state regulation in the OER process, thereby facilitating further design and engineering of flexible magnetic electrochemistry catalysts with promising potential.