Largely Enhanced Oxygen Evolution Performance in a Ferromagnetic Ruddlesden–Popper Phase Cobaltate

The oxygen evolution reaction (OER), as a key half-reaction in water splitting, plays a critical role in various energy conversion and storage systems. Novel high-performance catalysts have always been desirable. In this work, we have fabricated insulating perovskite LaCoO3 and its corresponding Ruddlesden–Popper (RP) phase La2CoO4 films. At room temperature, the perovskite LaCoO3 films are nonmagnetic while the RP phase La2CoO4 films are ferromagnetic. The magnetic RP phase La2CoO4 thin films exhibit significantly higher OER activities, with a nearly 70-fold increase in current density compared to the perovskite LaCoO3. Theoretical calculations indicate that the ferromagnetic order in the RP phase film substantially lowers the OER overpotential. This study highlights the potential of RP phase magnetic cobaltates for electrochemical water oxidation and magnetocatalysis applications.