Advances, practical applications, and future prospects of layered perovskite oxides (LnBaCo2O5+δ) for the electrocatalysis reactions

Abstract

To develop sustainable and clean energy, efficient and cost-effective production technologies have been explored. One of the most ways is considered to harness the power of intermittent renewable sources to drive high-performance fuel cells. Nowadays, the electrocatalysis reactions require scarce precious-metal catalysts along with poor long-term durability, such as Pt, Ru, and Ir etc. On the other hand, the-state-of-the-art simple perovskite and perovskite-like catalysts still show unsatisfactory performance under desired conditions. These issues limit large-scale commercial applications of these electrocatalysts. In past two decades, a family of A-site cation-ordered layered double perovskites (LnBaCo2O5+δ, Ln = lanthanide element) have attracted much attention because of adequate mixed ionic and electronic conductivity, fast surface oxygen exchange and ionic diffusion kinetics, and steered electronic structures. Therefore, many efforts have been devoted to design highly active, steady, and durable LnBaCo2O5+δ perovskites toward oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). Furthermore, we look forward to further utilize them as electrode catalysts for solid oxide fuel cells, solid oxide electrolysis cells, and overall water splitting. Herein this review aims to present an overview on advances of the LnBaCo2O5+δ perovskites with different crystal structures, including ORR, HER, and OER properties. The optimal perovskite components would be screened according to previous experimental and theoretical studies. More importantly, the effective descriptors (electronic structure-based descriptors, electronegativity, and tolerance factors) are discussed for describing the structure-performance relationship. In the context of the perovskite materials, the position of O 2p-band center relative to the Fermi level (EF) is closely correlated with basic physicochemical properties, e. g. the charge transfer energy (∆), formation energy of oxygen vacancy, binding energy of reaction intermediates on the catalyst surface, area-specific resistance, oxygen surface exchange and ionic diffusion coefficients. Besides, the tolerance factor (tf) is proposed to be another powerful tool for predicting the catalytic activity and stability of LnBaCo2O5+δ. In this review, we show how the electrochemical performance varies with such descriptors as mentioned above. This would supply an opportunity for opening up the performance predictions accurately, further accelerating the commercialization of efficient and environment-friendly technology.