The electrochemical performance of the perovskite complex was discovered to depend greatly on the different locations of the identical particle, which represent different surface charges accordingly. The surface charges were evaluated by Zeta potential (ζ) for the intrinsic BSCF5582 (Ba0.5Sr0.5Co0.8Fe0.2O3 -δ), ball-milled (BM-BSCF5582), and heat-treated in an oxygen atmosphere after ball-milling (48h-O2-BM-BSCF5582), the mean ζ of which represents -11.1, 21.2, and -6.1 mV, respectively, which reflects well on different surface chemistries. When the bonding structures at the different stratified layers and the overall crystalline morphologies were analyzed via X-ray photoelectron spectroscopy and high resolution transmission electron microscopy, respectively, the crystalline- and bonding-structure at the 50 nm depth of BSCF5582 is nearly identical to that of BM-BSCF5582 at the surface. As ball-milling proceeds, not only are particles comminuted but also the amorphous surface is broken open, leading to the revelation of inner and naïve cubic crystalline phase surfaces and affecting the catalytic activities of oxygen evolution reactions and oxygen reduction reactions positively and negatively, respectively, at significant scales.
Keywords: ball-milling; oxygen evolution reaction; oxygen reduction reaction; perovskites; surface charge.