Surface chemistry and porosity engineering through etching reveal ultrafast oxygen reduction kinetics below 400°C in B-site exposed (La,Sr)(Co,Fe)O3 thin-films

Oxides are critical materials for energy devices like solid oxide cells, catalysts, and membranes. Their performance is often limited by their catalytic activity at reduced temperatures. In this work, a simple etching process with acetic acid at room temperature was used to investigate how oxygen exchange is influenced by surface chemistry and mesoporous structuring in single-crystalline epitaxial (La0.60Sr0.40)(0.95)(Co0.20Fe0.80)O-3. Using low energy ion scattering and electrical measurements, it is shown that increasing the B-site transition metal cation surface exposure (most notably with Fe) leads to strongly reduced activation energy from E-a approximate to 1 eV to E-a approximate to 0.4 eV for oxygen exchange and an order of magnitude increased oxygen exchange kinetics below 400 degrees C. Increasing the active area by similar to 200% via mesoporous structuring leads to increased oxygen reduction rates by the same percentage. Density functional calculations indicate that a B-site exposed surface with high oxygen vacancy concentration can explain the experimental results. The work opens a pathway to tune surfaces and optimize oxygen exchange for energy devices.

Automated summary

This study investigates the effects of surface chemistry and mesoporous structuring on oxygen exchange by using an etching process with acetic acid. The results show that increasing the surface exposure of transition metal cations and the active area through mesoporous structuring can enhance the oxygen exchange kinetics, leading to optimized energy device performance.