La_0.2Sr_0.25Ca_0.45TiO₃ Surface Reactivity with H₂: A Combined Operando NEXAFS and Computational Study

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• A-site doped SrTiO3 is a potential alternative to traditional anode materials in solid oxide fuel cells (SOFCs).
• Understanding the reactivity and reducibility of these perovskite materials is crucial for optimizing SOFC performance.

Purpose of the Study:

• To investigate the reactivity of La0.2Sr0.25Ca0.45TiO3 (LCSTO), La0.2Sr0.7TiO3 (LSTO), and SrTiO3 (STO) towards H2.
• To correlate material synthesis methods with the reducibility of Ti4+ in perovskite structures.

Main Methods:

• Operando ambient pressure NEXAFS spectroscopy was employed to study the samples' reactivity.
• Theoretical spectra simulations were performed using the FDMNES code.
• Samples were synthesized via molecular beam epitaxy (MBE), hydrothermal, and modified-Pechini routes.

Main Results:

• The reducibility of the perovskite samples was found to be dependent on both stoichiometry and morphology.
• Material morphology, which influences reducibility, is determined by the chosen synthetic method.
• Insights into the reducibility of Ti4+ in perovskites were obtained.

Conclusions:

• The synthesis method plays a critical role in determining the morphology and subsequent reducibility of A-site doped SrTiO3.
• Optimizing synthesis routes can lead to improved performance of these materials in SOFC applications.