Chloride ion-capturing La0.7Sr0.3BO3 (B = Fe, Co) perovskite oxides achieving superior electrochemical desalination performance†

Perovskite oxides (ABO₃), with a designable crystal structure, excellent conductivity and inherent oxygen vacancies, hold great promise in addressing the sluggish kinetics and poor stability of conventional Cl⁻ capturing electrodes used in capacitive deionization (CDI) for saline water desalination. However, Cl⁻ storage in perovskite oxides remains largely unexplored in the CDI field. This work unprecedentedly demonstrates that Cl⁻ intercalation can be realized for perovskite oxides. The cell parameters and formation energies of a series of ABO₃ perovskite oxides were precisely predicted using machine learning (ML), while promising candidates (i.e., LaFeO₃ and LaCoO₃) for CDI were screened from unknown perovskite oxides. With partial substitution of Sr²⁺ at the A-site of LaFeO₃, the La_0.7Sr_0.3FeO₃ anode displays an excellent desalination rate (6.26 mg g min⁻¹) and superior stability (80% retention after 100-cycle desalination), comparable to state-of-the-art Cl⁻ capturing electrodes. The superior desalination performance is attributed to the reversible redox activity of the Fe ions and the abundant oxygen vacancies. The underlying mechanism was revealed through various quasi-in situ characterization studies and density functional theory calculations. This work pioneers the application of perovskite oxides in CDI and realizes the accelerated discovery of high-performance perovskite oxides for desalination via an ML approach.