Chemical pressure engineering of perovskite oxide nanoparticles for oxygen evolution

Perovskite oxides are well known for their excellent intrinsic activity toward the oxygen evolution reaction (OER) in alkaline media. However, precise control and a clear understanding of their active phases remain elusive. In this work, we demonstrate the effect of chemical pressure-induced strain through controlled substitution of isovalent La-site with Nd in sol-gel auto combustion-derived LaFeO₃ nanoparticles on the OER activities. Substitution of the smaller atom, Nd, at the La-site in LaFeO₃ generates inward chemical pressure, leading to the shrinkage of the LaFeO₃ lattice. This chemical pressure effect promotes the formation of oxygen vacancies and thereby tailors the Fe as an active site to significantly boost OER performance. Raman spectroscopy validates the structural distortion induced by chemical pressure in Nd-substituted LaFeO₃. Theoretical calculations reveal that Nd substitution at the La site shifts the band edges closer to the Fermi level. As a result, the Nd-substituted LaFeO₃ electrocatalyst, particularly La₀.₆Nd₀.₄FeO₃ nanoparticles, exhibits excellent OER performance with an impressively low overpotential of 179 mV for 10 mA cm⁻². This study provides both experimental and theoretical evidence towards linking chemical pressure effects and oxygen vacancy formation in Nd substituted LaFeO₃ perovskites.