The oxygen reduction reaction (ORR) is an important electrode reaction for energy storage and conversion devices based on oxygen electrocatalysis. This paper introduces the thermodynamics, reaction kinetics, reaction mechanisms, and reaction pathways of ORR in aqueous alkaline media. Recent advances of the catalysts for ORR were extensively reviewed, including precious metals, nonmetal-doped carbon, carbon–transition metal hybrids, transition metal oxides with spinel and perovskite structures, and so forth. The applications of those ORR catalysts to zinc–air batteries and alkaline fuel cells were briefly introduced. A concluding remark summarizes the current status of the reaction pathways, advanced catalysts, and the future challenges of the research and development of ORR.

Oxygen Reduction in Alkaline Media: From Mechanisms to Recent Advances of Catalysts

Reduction/Evolution Catalysts for Low-Temperature Electrochemical Devices Dengjie Chen,†,⊥,∇ Chi Chen,†,⊥ Zarah Medina Baiyee,† Zongping Shao,‡,§ and Francesco Ciucci*,†,∥ †Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China ‡State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry & Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009, China Department of Chemical Engineering, Curtin University, Perth, Western Australia 6845, Australia Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Nonstoichiometric Oxides as Low-Cost and Highly-Efficient Oxygen Reduction/Evolution Catalysts for Low-Temperature Electrochemical Devices

The oxygen reduction reaction (ORR) is one of the most important electrochemical reactions in energy conversion and storage technologies, such as fuel cells and metal–air batteries. However, the sluggish kinetics of the ORR is a key factor limiting the performance of these energy storage and conversion devices. Perovskite oxides are a promising family of electrocatalysts for the ORR because of their unique physical and chemical properties, such as variable crystal structure and non-stoichiometric chemistry. Studies have shown that the catalytic properties of perovskite oxides in the ORR are largely related to oxygen vacancies, which alter their electronic and crystal structures and surface chemistry. This review summarizes recent research advances on understanding the role of oxygen vacancies of the ABO3 perovskite oxides in catalyzing the ORR. With a brief introduction of perovskite oxides, approaches to creating oxygen vacancies in the ABO3 perovskite oxides and the role of oxygen vacancies in improving their catalytic performance for the ORR are discussed. Research perspectives in this important area are highlighted.

The role of oxygen vacancies of ABO3 perovskite oxides in the oxygen reduction reaction

There is a need to reduce the use of noble metal elements—especially in the field of catalysis, where noble metals are ubiquitously applied. To this end, perovskite oxides, an important class of mixed oxide, have been attracting increasing attention for decades as potential replacements. Benefiting from the extraordinary tunability of their compositions and structures, perovskite oxides can be rationally tailored and equipped with targeted physical and chemical properties—for example, redox behavior, oxygen mobility, and ionic conductivity—for enhanced catalysis. Recently, the development of highly efficient perovskite oxide catalysts has been extensively studied. This perspective article summarizes the recent development of lanthanum-based perovskite oxides as advanced catalysts for both energy conversion applications and traditional heterogeneous reactions.

Recent Advances of Lanthanum-Based Perovskite Oxides for Catalysis

The sluggish kinetics of the oxygen reduction reaction (ORR) limit the efficiency of numerous oxygen-based energy conversion devices such as fuel cells and metal-air batteries. Among earth abundant catalysts, manganese-based oxides have the highest activities approaching that of precious metals. In this Review, we summarize and analyze literature findings to highlight key parameters that influence the catalysis of the ORR on manganese-based oxides, including the number of electrons transferred as well as specific and mass activities. These insights can help develop design guides for highly active ORR catalysts and shape future fundamental research to gain new knowledge regarding the molecular mechanism of ORR catalysis.

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Recent Insights into Manganese Oxides in Catalyzing Oxygen Reduction Kinetics

https://istina.msu.ru/media/publications/article/23e/24f/11542560/1-s2.0-S0013468615307842-main.pdf

Rationalizing the Influence of the Mn(IV)/Mn(III) Red-Ox Transition on the Electrocatalytic Activity of Manganese Oxides in the Oxygen Reduction Reaction

The mechanism of the oxygen reduction reaction (ORR) on LaCoO(3) and La(0.8)Sr(0.2)MnO(3) perovskite oxides is studied in 1 M NaOH by using the rotating ring disc electrode (RRDE) method. By combining experimental studies with kinetic modeling, it was demonstrated that on perovskite, as well as on perovskite/carbon electrodes, the ORR follows a series pathway through the intermediate formation of hydrogen peroxide. The escape of this intermediate from the electrode strongly depends on: 1) The loading of perovskite; high loadings lead to an overall 4 e(-) oxygen reduction due to efficient hydrogen peroxide re-adsorption on the active sites and its further reduction. 2) The addition of carbon to the catalytic layer, which affects both the utilization of the perovskite surface and the production of hydrogen peroxide. 3) The type of oxide; La(0.8)Sr(0.2)MnO(3) displays higher (compared to LaCoO(3)) activity in the reduction of oxygen to hydrogen peroxide and in the reduction/oxidation of the latter.

Electrocatalytic Oxygen Reduction Reaction on Perovskite Oxides: Series versus Direct Pathway

Hydrogen peroxide has been identified as a stable intermediate of the electrochemical oxygen reduction reaction on various electrodes including metal, metal oxide and carbon materials. In this article we study the hydrogen peroxide oxidation and reduction reactions in alkaline medium using a rotating disc electrode (RDE) method on oxides of the perovskite family (LaCoO3, LaMnO3 and La0.8Sr0.2MnO3) which are considered as promising electrocatalytic materials for the cathode of liquid and solid alkaline fuel cells. The experimental findings, such as the higher activity of Mn-compared to that of Co-perovskites, the shape of RDE curves, and the influence of the H2O2 concentration, are rationalized with the help of a microkinetic model.

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Electrocatalysis of hydrogen peroxide reactions on perovskite oxides: experiment versus kinetic modeling

Hydrogen peroxide has been detected as a reaction intermediate in the electrochemical oxygen reduction reaction (ORR) on transition-metal oxides and other electrode materials. In this work, we studied the electrocatalytic and catalytic reactions of hydrogen peroxide on a set of Mn oxides, Mn2O3, MnOOH, LaMnO3, MnO2, and Mn3O4, that adopt different crystal structures to shed light on the mechanism of the ORR on these materials. We then combined experiment with kinetic modeling with the objective to correlate the differences in the ORR activity to the kinetics of the elementary reaction steps, and we uncovered the importance of structural and compositional factors in the catalytic activity of the Mn oxides. We concluded that the exceptional activity of Mn2O3 in the ORR is due to its high catalytic activity both in the reduction of oxygen to hydrogen peroxide and in the decomposition of the latter, and furthermore, we proposed a tentative link between crystal structure and reactivity.

Tiphaine Poux

Papers

Rationalizing the Influence of the Mn(IV)/Mn(III) Red-Ox Transition on the Electrocatalytic Activity of Manganese Oxides in the Oxygen Reduction Reaction

Electrocatalytic Oxygen Reduction Reaction on Perovskite Oxides: Series versus Direct Pathway

Electrocatalysis of hydrogen peroxide reactions on perovskite oxides: experiment versus kinetic modeling

Study of Hydrogen Peroxide Reactions on Manganese Oxides as a Tool To Decode the Oxygen Reduction Reaction Mechanism