Control of crystallographic orientation in Ruddlesden-Popper for fast oxygen reduction

Designing oxide materials to achieve the high oxygen reduction reaction (ORR) activity is a key requirement to facilitate the development of energy and environmental applications. Manipulating the crystallographic planes of layered oxides has an impact on determining the electrocatalytic activity. However, the correlation between the ORR kinetics and the crystallographic orientations is not fully understood in a single material system. Here, a superconducting oxide, La1.85Sr0.15CuO4-δ (LSC214) is used to demonstrate that the crystallographic orientation plays a crucial role in controlling the ORR activity. The (114)-oriented epitaxial LSC214 films show dramatically enhanced ORR activity up to two orders of magnitude compared to the (001)- and (103)-oriented LSC214 films. We attribute the enhanced ORR activity of the LSC214 films to both the exposed oxygen migration channels and the increased oxygen vacancies. Our study provides a new design strategy to enhance the ORR activity for high-performance energy applications and illustrates that the control of orientation is a simple means to tune the electrocatalytic activity. [Display omitted] •The orientation of epitaxial Ruddlesden-Popper (RP) oxide thin films was controlled.•The kq values of RP oxides were enhanced (~2 orders) by controlling the orientation.•Controlling the crystalline anisotropy modulated the electrocatalytic activity.•The relationship of orientation-electrochemical property in RP oxides was revealed.