Harnessing oxygen electrocatalysis through exsolved Pt nanoparticles from La0.6Sr0.4Fe0.95Pt0.05O3-δ

• Controlled reduction creates Pt-reduced nanoparticles and surface defects. • Exsolved ∼1.2 nm Pt-reduced nanoparticles boost oxygen electrocatalysis. • Distribution of relaxation times analysis indicated enhanced charge transfer. • Post-mortem O K-edge XAS suggested surface restructuring due to Pt exsolution. This work explores the exsolution of well-dispersed nanoparticles containing reduced Pt species from La 0.6 Sr 0.4 Fe 0.95 Pt 0.05 O 3-δ (LSFPt) as an effective approach to design catalysts for oxygen electrocatalysis. A 10 h reduction treatment at 500 °C in 5% H 2 /Ar promotes the exsolution of ∼1.2 nm Pt nanoparticles on the surface, increasing oxygen deficiency without compromising the perovskite structure. The resulting catalyst exhibits over 2.5-fold performance improvement for oxygen evolution reaction (OER) and reduction reaction (ORR) in alkaline media compared to the as-prepared LSFPt. Specifically, OER potential decreased from 1.61 to 1.58 V RHE , while the ORR potential improved from 0.31 to 0.48 V RHE . Electrochemical impedance spectroscopy (EIS), combined with distribution of relaxation times (DRT) deconvolution analysis, revealed a notable decrease in medium-frequency resistance, indicating enhanced charge transfer at the electrode surface for OER and ORR. Post-mortem O K-edge spectra obtained by soft X-ray absorption spectroscopy in total electron yield mode further suggest an increased surface restructuring in the reduced LSFPt, attributed to the synergistic presence of surface defects and exsolved nanoparticles containing reduced Pt species. This one-step reduction protocol provides a valuable methodological insight for designing catalysts for oxygen electrocatalysis by tailoring the surface composition of perovskite material aligned with the necessity for bifunctional systems.