The Synergistic Effect Accelerates the Oxygen Reduction/Evolution Reaction in a Zn-Air Battery

Research Progress of Perovskite-Based Bifunctional Oxygen Electrocatalyst in Alkaline Conditions

In light of the depletion of conventional energy sources, it is imperative to conduct research and development on sustainable alternative energy sources. Currently, electrochemical energy storage and conversion technologies such as fuel cells and metal-air batteries rely heavily on precious metal catalysts like Pt/C and IrO2, which hinders their sustainable commercial development. Therefore, researchers have devoted significant attention to non-precious metal-based catalysts that exhibit high efficiency, low cost, and environmental friendliness. Among them, perovskite oxides possess low-cost and abundant reserves, as well as flexible oxidation valence states and a multi-defect surface. Due to their advantageous structural characteristics and easily adjustable physicochemical properties, extensive research has been conducted on perovskite-based oxides. However, these materials also exhibit drawbacks such as poor intrinsic activity, limited specific surface area, and relatively low apparent catalytic activity compared to precious metal catalysts. To address these limitations, current research is focused on enhancing the physicochemical properties of perovskite-based oxides. The catalytic activity and stability of perovskite-based oxides in Oxygen Reduction Reaction/Oxygen Evolution Reaction (ORR/OER) can be enhanced using crystallographic structure tuning, cationic regulation, anionic regulation, and nano-processing. Furthermore, extensive research has been conducted on the composite processing of perovskite oxides with other materials, which has demonstrated enhanced catalytic performance. Based on these different ORR/OER modification strategies, the future challenges of perovskite-based bifunctional oxygen electrocatalysts are discussed alongside their development prospects.

Perovskite-based electrocatalysts for oxygen evolution reaction in alkaline media: A mini review

Water electrolysis is one of the attractive technologies for producing clean and sustainable hydrogen fuels with high purity. Among the various kinds of water electrolysis systems, anion exchange membrane water electrolysis has received much attention by combining the advantages of alkaline water electrolysis and proton exchange membrane water electrolysis. However, the sluggish kinetics of the oxygen evolution reaction, which is based on multiple and complex reaction mechanisms, is regarded as a major obstacle for the development of high-efficiency water electrolysis. Therefore, the development of high-performance oxygen evolution reaction electrocatalysts is a prerequisite for the commercialization and wide application of water electrolysis systems. This mini review highlights the current progress of representative oxygen evolution reaction electrocatalysts that are based on a perovskite structure in alkaline media. We first summarize the research status of various kinds of perovskite-based oxygen evolution reaction electrocatalysts, reaction mechanisms and activity descriptors. Finally, the challenges facing the development of perovskite-based oxygen evolution reaction electrocatalysts and a perspective on their future are discussed.

Perovskite With Tunable Active-Sites Oxidation State by High-Valence W for Enhanced Oxygen Evolution Reaction

Perovskite oxides have been established as a promising kind of catalyst for alkaline oxygen evolution reactions (OER), because of their regulated non-precious metal components. However, the surface lattice is amorphous during the reaction, which gradually decreases the intrinsic activity and stability of catalysts. Herein, the precisely control tungsten atoms substituted perovskite oxides (Pr_0.5Ba_0.5Co_1-xW_xO₃-_δ) nanowires were developed by electrostatic spinning. The activity and Tafel slope were both dependent on the W content in a volcano-like fashion, and the optimized Pr_0.5Ba_0.5Co_0.8W_0.2O₃-_δ exhibits both excellent activity and superior stability compared with other reported perovskite oxides. Due to the outermost vacant orbitals of W⁶⁺, the electronic structure of cobalt sites could be efficiently optimized. Meanwhile, the stronger W-O bond could also significantly improve the stability of latticed oxide atoms to impede the generation of surface amorphous layers, which shows good application value in alkaline water splitting.

Silver decorated cobalt carbonate to enable high bifunctional activity for oxygen electrocatalysis and rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) is primarily driven by the couple of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Currently,it is still challenging to develop cost-effective, highly efficient, and robust bifunctional catalysts for ZABs. Herein, a novel silver decorated cobalt carbonate (Ag@CoCO₃) hybrid catalyst is proposed as the potential bifunctional catalyst to drive OER and ORR for ZABs. Engineering Ag nanoparticles onto the surface of CoCO₃ microsphere not only facilitates the charge transfer, but also modulates the electronic structure, which are beneficial to intrinsic bifunctional activity. As a result, this Ag@CoCO₃ catalyst yields a substantially enhanced bifunctionality compared to the pristine CoCO₃ catalyst. Moreover, the homemade Ag@CoCO₃ based ZABs provides a high peak power density of 146 mW cm^-2, superior to 107 mW cm^-2 for CoCO₃ based ZABs and 111 mW cm^-2 for commercial Pt/C-IrO₂ based ZABs.

High-Efficiency of Bi-Functional-Based Perovskite Nanocomposite for Oxygen Evolution and Oxygen Reduction Reaction: An Overview

High efficient, low-cost and environmentally friendly-natured bi-functional-based perovskite electrode catalysts (BFPEC) are receiving increasing attention for oxygen reduction/oxygen evolution reaction (ORR/OER), playing an important role in the electrochemical energy conversion process using fuel cells and rechargeable batteries. Herein, we highlighted the different kinds of synthesis routes, morphological studies and electrode catalysts with A-site and B-site substitution co-substitution, generating oxygen vacancies studies for boosting ORR and OER activities. However, perovskite is a novel type of oxide family, which shows the state-of-art electrocatalytic performances in energy storage device applications. In this review article, we go through different types of BFPECs that have received massive appreciation and various strategies to promote their electrocatalytic activities (ORR/OER). Based on these various properties and their applications of BFPEC for ORR/OER, the general mechanism, catalytic performance and future outlook of these electrode catalysts have also been discussed.

Co/CoP Nanoparticles Encapsulated Within N, P-Doped Carbon Nanotubes on Nanoporous Metal-Organic Framework Nanosheets for Oxygen Reduction and Oxygen Evolution Reactions

Herein, Co/CoP nanoparticles encapsulated with N, P-doped carbon nanotubes derived from the atomic layer deposited hexagonal metal-organic frameworks (MOFs) are obtained by calcinations and subsequent phosphating and are employed as electrocatalyst. The electrocatalytic performance evaluations show that the as-prepared electrocatalyst exhibits an overpotential of 342 mV at current density of 10 mA cm-2 and the Tafel slope of 74 mV dec-1 for oxygen evolution reaction (OER), which is superior to the most advanced ruthenium oxide electrocatalyst. The electrocatalyst also shows better stability than the benchmark RuO2. After 9 h, the current density is only decreased by 10%, which is far less than the loss of RuO2. Moreover, its onset potential for oxygen reduction reaction (ORR) is 0.93 V and follows the ideal 4-electron approach. After the stability test, the current density of the electrocatalyst retains 94% of the initial value, which is better than Pt/C. The above results indicate that the electrocatalyst has bifunctional activity and excellent stability both for OER and ORR. It is believed that this strategy provides guidance for the synthesis of cobalt phosphide/carbon-based electrocatalysts.

Electrochemical Performance of Ba0.5Sr0.5Co0.8Fe0.2O3-δ in Symmetric Cells With Sm0.2Ce0.8O1.9 Electrolyte for Nitric Oxide Reduction Reaction

The emission of nitric oxide from the combustion process of fossil fuels causes air pollution problems. In addition to traditional removal methods, nitric oxide can be removed by the electrochemical reduction method. In this study, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ powders were synthesized using a solid-state reaction method. Symmetrical cells, with Sm_0.2Ce_0.8O_1.9 as the electrolyte and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ as the electrodes, were prepared as the electrochemical reactor for nitric oxide reduction. In the process of electrochemical reduction, nitric oxide reduction occurs at the cathode and oxygen evolution occurs at the anode. To study the nitric oxide reduction performance of the electrode, impedances of the symmetrical cell in different atmospheres were analyzed. For the nitric oxide conversion in symmetric cells, two different modes, dual chamber and single chamber, were applied. Results demonstrated that the denitrification performance of the double chamber was better but the single chamber mode had other advantages in its simple structure. Presliminary stability results of the single chamber symmetric cell show that the electrochemical reduction of nitric oxide in symmetric cells with BSCF performed most reliably.