Progress in Oxygen Reduction Reaction Electrocatalysts for Metal-Air Batteries

Abstract

With the intensification of the global energy crisis and the deterioration of ecological environment, the exploitation and utilization of sustainable energy have gained more attention. Metal-air battery as a kind of high-performance green energy may become one of the most promising next-generation battery technologies. Compared to conventional storage batteries such as Zn-Mn and lead-acid batteries, metal-air battery has higher theoretical energy density, especially Li-air battery with an extremely high theoretical density 3505 Wh/kg. Such high energy density is due to the fact that oxygen is not stored in the cell. Other advantages include stable potential, low cost and environmental friendship. However, there are many important factors that limit its commercial application. Among them, a critical issue is the sluggish kinetics of cathodic oxygen reduction reaction (ORR), so it is necessary to develop ORR catalytic materials for enhancing the kinetics. Recently, there are many researches about ORR catalysts. In addition to a brief introduction of the reaction mechanism of ORR, the paper introduced the current research progress of four groups of cathodic catalysts including noble metal and its alloys, transition-metal oxides/sulfides, functional carbon materials and metal nitrides. However, there are still many problems, such as the lack of fundamental mechanistic study, high cost of Pt-based catalyst, uncertain active site of functional carbon materials and low activity for non-noble metal catalysts. In summary, great efforts should be needed. Based on this, the authors pointed out the development direction for ORR catalysts. The future research direction of cathodic catalysts would include: (1) researching the elusive oxygen reaction mechanism and defining the active sites, (2) studying the effect of physical structure parameters (e.g., structure, morphology, size) on the activity and optimizing synthesis conditions of catalysts to obtain better activity and stability, (3) developing novel efficient and inexpensive catalysts in according to the oxygen reaction mechanism.

Co3O4 Hollow Polyhedrons as Bifunctional Electrocatalysts for Reduction and Evolution Reactions of Oxygen

“…However, the disadvantages of these precious metal‐based electrocatalysts are prohibitive cost, low abundance, and poor stability . Thus, it is necessary to discover the earth‐abundant, highly efficient, and inexpensive nonprecious metal‐based materials that can be used as bifunctional electrocatalysts for ORR and OER …”

Framework and Catalytic Activity of a Metallomicelle System Made from an Azacrown Ether, Lanthanum(III) Ion and a Cationic Surfactant

“…Fluorescence spectroscopy can also be used to study the interaction between a metal ion and a ligand; when the a binding interaction between the metal ion and ligand occurs, the fluorescence intensity of the system is enhanced or weakened. This means that the energy transfer occurs between the metal ion and ligand, which causes the fluorescence of the complexes to be weakened or enhanced [22]. In order to demonstrate this type of interaction in our system, we analysed the fluorescence intensity changes on addition of lanthanum(III) to the ligand solution, and the results are shown in Figure 2.…”

A Review of Carbon-based Non-noble Catalysts for Oxygen Reduction Reaction

“…为了彻底解决 PEMFC 阴极贵金属催化剂的问题, 非贵金属 ORR 催化剂成为近年的研究热点, 也取得了 巨大进展. 按照催化剂材料的不同, 可以将非贵金属催 化剂分为两大类 [1] : [12,13] . 在众多过渡金属大 环化合物中 N 4 -金属大环化合物, 尤其是 Fe、 Co 的酞菁、 卟啉表现出了最好的 ORR 催化活性.…”