Development of cost-effective and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of prime importance to emerging renewable energy technologies. Here, we report a simple and effective strategy for enhancing ORR and OER electrocatalytic activity in alkaline solution by introducing Asite cation deficiency in LaFeO 3 perovskite; the enhancement effect is more pronounced for the OER than the ORR. Among the A-site cation deficient perovskites studied, La 0.95 FeO 3-δ (L0.95F) demonstrates the highest ORR and OER activity and, hence, the best bifunctionality. The dramatic enhancement is attributed to the creation of surface oxygen vacancies and a small amount of Fe 4+ species. This work highlights the importance of tuning cation deficiency in perovskites as an effective strategy for enhancing ORR and OER activity for applications in various oxygen-based energy storage and conversion processes.

The development of highly efficient and low‐cost electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting associated with the storage of clean and renewable energy. Here, this study reports its findings in the development of a nanostructured perovskite oxide as OER/HER bifunctional electrocatalyst for overall water splitting. Prepared by a facile electrospinning method, SrNb0.1Co0.7Fe0.2O3–δ perovskite nanorods (SNCF‐NRs) display excellent OER and HER activity and stability in an alkaline solution, benefiting from the catalytic nature of perovskites and unique structural features. More importantly, the SNCF‐NR delivers a current density of 10 mA cm−2 at a cell voltage of merely ≈1.68 V while maintaining remarkable durability when used as both anodic and cathodic catalysts in an alkaline water electrolyzer. The performance of this bifunctional perovskite material is among the best ever reported for overall water splitting, offering a cost‐effective alternative to noble metal based electrocatalysts.

The perovskite SrNb0.1 Co0.7 Fe0.2 O3-δ (SNCF) is a promising OER electrocatalyst for the oxygen evolution reaction (OER), with remarkable activity and stability in alkaline solutions. This catalyst exhibits a higher intrinsic OER activity, a smaller Tafel slope and better stability than the state-of-the-art precious-metal IrO2 catalyst and the well-known BSCF perovskite. The mass activity and stability are further improved by ball milling. Several factors including the optimized eg orbital filling, good ionic and charge transfer abilities, as well as high OH(-) adsorption and O2 desorption capabilities possibly contribute to the excellent OER activity.

Metal oxide-based materials are emerging as a promising family of hydrogen evolution reaction (HER) electrocatalysts.

Oxygen electrocatalysis, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), plays an extremely important role in oxygen-based renewable-energy technologies such as rechargeable metal-air batteries, regenerative fuel cells and water splitting. Perovskite oxides have recently attracted increasing interest and hold great promise as efficient ORR and OER catalysts to replace noble-metal-based catalysts, owing to their high intrinsic catalytic activity, abundant variety, low cost, and rich resources. The introduction of perovskite-carbon interfaces by forming perovskite/carbon composites may bring a synergistic effect between the two phases, thus benefiting the oxygen electrocatalysis. This review provides a comprehensive overview of recent advances in perovskite/carbon composites for oxygen electrocatalysis in alkaline media, aiming to provide insights into the key parameters that influence the ORR/OER performance of the composites, including the physical/chemical properties and morphologies of the perovskites, the multiple roles of carbon, the synthetic method and the synergistic effect. A special emphasis is placed on the origin of the synergistic effect associated with the interfacial interaction between the perovskite and the carbon phases for enhanced ORR/OER performance. Finally, the existing challenges and the future directions for the synthesis and development of more efficient oxygen catalysts based on perovskite/carbon composites are proposed.

1 wileyonlinelibrary.com evolution reaction (OER) is currently the limiting factor on the water splitting due to its sluggish kinetics involving the complex four-electron oxidation process. [3] To this end, the presence of an efficient OER electrocatalyst is essential to obtain an accelerated reaction rate. At present, precious metal-based iridium and ruthenium oxides (i.e., IrO 2 and RuO 2 ) are regarded as the OER catalysts benchmarks, [4] but their scarcity and high cost have hindered their wide-scale applications. IrO 2 and RuO 2 catalysts additionally show poor stability during long-term operation in alkaline solutions. [5] As such, tremendous efforts have been devoted to develop low-cost and earth-abundant alternative OER catalysts with high activity and good stability.Over the past few decades, due to their compositional and structural flexibility, precious metal-free perovskitetype oxides with a general formula of ABO 3 (A = alkaline-earth or rare-earth metals and B = transition metals) have attracted interests in various applications, e.g., solid oxide fuel cells (SOFCs), oxygen permeation membranes, metalair batteries, and supercapacitors. [6] Most recently, they were reported to also exhibit high OER activity in an alkaline solution. [7] Rossmeisl group and Koper group theoretically calculated that SrCoO 3 parent oxide would deliver the highest OER activity among LaMO 3 and SrMO 3 (M = transition metals) parent oxides via density functional theory calculations. [8] Shao-Horn and co-workers reported that one of the Developing cost-effective and efficient electrocatalysts for oxygen evolution reaction (OER) is of paramount importance for the storage of renewable energies. Perovskite oxides serve as attractive candidates given their structural and compositional flexibility in addition to high intrinsic catalytic activity. In a departure from the conventional doping approach utilizing metal elements only, here it is shown that non-metal element doping provides an another attractive avenue to optimize the structure stability and OER performance of perovskite oxides. This is exemplified by a novel tetragonal perovskite developed in this work, i.e., SrCo 0.95 P 0.05 O 3-δ (SCP) which features higher electrical conductivity and larger amount of O 2 2− /O − species relative to the non-doped parent SrCoO 3-δ (SC), and thus shows improved OER activity. Also, the performance of SCP compares favorably to that of well-developed perovskite oxides reported. More importantly, an unusual activation process with enhanced activity during accelerated durability test (ADT) is observed for SCP, whereas SC delivers deactivation for the OER. Such an activation phenomenon for SCP may be primarily attributed to the in situ formation of active A-site-deficient structure on the surface and the increased electrochemical surface area during ADT. The concept presented here bolsters the prospect to develop a viable alternative to precious metal-based catalysts.

Layered LiCo0.8 Fe0.2 O2 demonstrates dramatically enhanced oxygen evolution reaction (OER) activity and durability in an alkaline solution over LiCoO2 and other reported state-of-the-art catalysts, including benchmark IrO2 . This superior performance is attributed to Fe-doping-induced synergistic effects.

A synergistic co‐doping strategy is proposed to identify a series of BaCo0.9–xFexSn0.1O3–δ perovskites with tunable electrocatalytic activity for the oxygen evolution reaction (OER). Simply through tailoring the relative concentrations of less OER‐active tin and iron dopants, a cubic perovskite structure (BaCo0.7Fe0.2Sn0.1O3–δ) is stabilized, showing intrinsic OER activity >1 order of magnitude larger than IrO2 and a Tafel slope of 69 mV dec−1.