README File Conductivity.zip - Conductivity measurements of the perovskite nanoparticles without conductive additives. Measured using ex situ 4-wire impedance spectroscopy. Electrochemistry.zip - The raw files of the RDE measurements conducted on the perovskite samples. XRD - XRD spectra of perovskite samples. XAS - the raw data of the XAS measurements, both operando and ex-situ and oxidation state references. The XAS spectra are given before and after normalization.