Suppression of surface amorphization during oxygen evolution reaction in A-site deficient perovskite oxides

Abstract Surface restructuring and the formation of amorphous layers during the initial stages of the oxygen evolution reaction (OER) is a common phenomenon in perovskite-based catalysts. It has also been observed that catalysts following the lattice oxygen mechanism (LOM) are prone to amorphization as the rates of lattice oxygen evolution and oxygen vacancy replenishment are not equal. This is accompanied by a significant A-site cation loss in the electrolyte, ultimately leading to the collapse of the crystalline phase and the appearance of an amorphous catalytic surface of a thickness of around 10 nm. Typically, the originally crystalline material is termed as precatalyst. In this work, we hypothesize that A-site deficient perovskite precatalysts of the family of Ba x Gd y La z Co 2 O 3- δ (BGLCxyz), which operate under LOM, will have a reduced degree or no surface amorphization under OER conditions in alkaline media. For this reason, A-site deficient BGLC587 with a 20% deficiency is synthesized to validate our main hypothesis. Furthermore, thermal reduction of the A-site deficient BGLC587 precatalyst is expected, to form embedded nanoparticles on its surface through the process of exsolution, thus inducing higher surface area and improved electrocatalytic activity, while still suppressing surface amorphization.