Transition metal (Fe, Co, Ni, and Mn) oxides for oxygen reduction and evolution bifunctional catalysts in alkaline media

Abstract

In recent years, a large amount of focus has been given to the development of alternative energy sources that are clean and efficient; among these, electrochemical energy holds potential for its compatibility with solar and wind energy, as well as its applications in metal-metal and metal-air batteries. However, these technologies require the use of a catalyst to make this application feasible. Current catalysts consist of precious metals such as platinum, which are expensive and block common access to electrochemical energy. Transition metals, and their oxides, serve as a promising alternative to these precious metals. A wide range of these metals, including cobalt, manganese, nickel, and iron, have been researched as bifunctional catalysts, capable of driving both the storage and discharge of energy. Not only do they show innate electrochemical capabilities, but their structural diversity, as well as their ability to be mixed, doped, and combined with other materials such as graphene, make transition metal oxides a

Design of Efficient Bifunctional Oxygen Reduction/Evolution Electrocatalyst: Recent Advances and Perspectives

“…Thus, spinel and perovskite structure with multi-metal components are largely used for ORR and OER catalysis. [32] Spinel oxides (A x B 3−x O 4 ) can be used as bifunctional ORR/OER catalyst in alkaline media. [46] Among spinel oxides, the electron transfer occur with quite low activation energy between the cations of different valences.…”

“…[32] Thus, the formation of RuO 2 /MnO 2 composite is promising for bifunctional ORR/OER. For example, Sun et al reported the synthesis of RuO 2 nanoparticles supported on MnO 2 nanorods (np-RuO 2 /nr-MnO 2 ) via a two-step hydrothermal reaction.…”

Enhancing Catalyst Efficiency of Activated Carbon for Oxygen Reduction Reaction in Air Cathode Microbial Fuel Cell Application

“…Besides, these metals can easily change from one oxidation state to another therefore it gives them the ability to tolerate the unchanging reduction and oxidation reactions which take place inside an electrolytic cell, thus improving stability [26,77]. Due to their natural activities, adequate stability in oxidative electrochemical environments, their structural multiplicity, as well as their ability to be mixed, doped, and to be fused with other materials such as carbon and graphene; transition metals and their oxides are regarded as promising way of enhancing AC catalytic activity [26,78]. Various transition metals like cobalt [27,79], manganese [29,77], nickel [80] and iron, have been mostly used as AC dopant for catalysis of oxygen reduction reaction (ORR) among a wide range of these metals.…”

“…The same array of ORR catalytic activity performance for these metals was observed which is consistent with the order of their active sites contents, fortunately Fe is the most abundant metal on earth which makes it a good candidate for this application. However, Fe when used in acidic media suffer from a lower catalytic activity, and from stability issues [26].…”

“…Platinum (Pt) is a commonly used catalyst however high-cost [24], low availability and poor stability [25] of this noble metal makes it difficult for massive production of cathodes, thus hinder MFCs scale up for practical application [26]. Alternatives to Pt includes inexpensive non-noble metal materials and their oxides such as transition metal Co [21,27], Fe 3 O 4 [28] and MnO 2 [29].…”