Authors: Armand J Lannerd | Chris Bartel
Source: ECS Meeting Abstracts (article, 2025-11-24)
Field: Materials Science — Electronic, Optical and Magnetic Materials

First-Principles Investigation of Protonation vs. Oxygen Vacancy Formation in La <sub>1-X</sub> Sr <sub>x</sub> CoO <sub>3-δ</sub> The rapid expansion of cloud computing and artificial intelligence technologies is dramatically increasing data center power consumption [1]. Advances in memory and computing are critical to improving the performance and minimizing the carbon footprint of these technologies. Electric-field control of metal oxides via electrochemical mechanisms offers a promising route to energy-efficient electronics, from low-power voltage-switched magnetic memory elements to neuromorphic computing devices [2]. La 1-x Sr x CoO 3-δ (LSCO) has been widely studied as an active material in the electrochemical setting, particularly in electric double-layer transistors. In these devices, a gating voltage is applied across an electrolyte in contact with LSCO. While pristine LSCO adopts a perovskite structure, gating induces oxygen vacancy formation, with an eventual topotactic transition to an orthorhombic brownmillerite phase (nominally δ = 0.5). Accompanying oxygen vacancy formation is structural expansion, a metal-to-insulator transition, and changes in magnetic ordering from ferromagnetic to weakly ferromagnetic or antiferromagnetic [3,4]. Extensive experimental and computational studies have focused on oxygen vacancy formation, but recent studies indicate that the water content of the environment influences the response of LSCO, pointing to the possibility of alternative redox mechanisms. The plausibility of proton insertion in LSCO and its effect on properties remains understudied. This first-principles study examines the thermodynamic competition between proton insertion and oxygen vacancy formation under relevant thermochemical and electrochemical conditions. Additionally, we investigate the structural and electronic consequences of protonation and compare with relevant experimental measurements. This work advances fundamental understanding of multi-ion redox behavior in non-stoichiometric oxides with implications for low-power voltage-regulated electronic applications. [1] Shehabi, A.; Smith, S. J.; Hubbard, A.; Newkirk, A.; Lei, N.; Siddik, M. A. B.; Holecek, B.; Koomey, J.; Masanet, E.; Sartor, D. 2024 United States Data Center Energy Usage Report ; Lawrence Berkeley National Laboratory: Berkeley, CA, 2024. [2] Leighton, C. Electrolyte-Based Ionic Control of Functional Oxides. Nat. Mater. 2019 , 18 (1), 13–18. [3] Chaturvedi, V.; Postiglione, W. M.; Chakraborty, R. D.; Yu, B.; Tabiś, W.; Hameed, S.; Biniskos, N.; Jacobson, A.; Zhang, Z.; Zhou, H.; Greven, M.; Ferry, V. E.; Leighton, C. Doping- and Strain-Dependent Electrolyte-Gate-Induced Perovskite to Brownmillerite Transformation in Epitaxial La1–xSrxCoO3−δ Films. ACS Appl. Mater. Interfaces 2021 , 13 (43), 51205–51217. [4] Postiglione, W. M.; Liang, J.; Nandakumaran, N.; Figari, L.; Aczel, A. A.; Leighton, C. Direct Neutron-Diffraction-Based Measurement of Magnetic Order in Brownmillerite SrCoO2.5 and La0.5Sr0.5CoO2.5 Thin Films. APL Mater. 2024 , 12 (4), 041123. Vacancy defect ; Perovskite (structure) ; Orthorhombic crystal system ; Ferromagnetism ; Brownmillerite ; Electrolyte ; Oxygen ; Electrochemistry Magnetic and transport properties of perovskites and related materials ; Electronic and Structural Properties of Oxides ; Advancements in Solid Oxide Fuel Cells