Recent Advances in the Development of Single‐Atom Catalysts for Oxygen Electrocatalysis and Zinc–Air Batteries

Abstract

satisfying only ≈10% of global energy demand. [1] Efficiently harnessing renewable energy sources at large scale, especially solar, hydroelectric, and wind power, has the potential to allow a progressive transition away from fossil fuel energy and curbing of anthropogenic CO 2 emissions responsible for global warming. [2] However, these renewable energy sources have the disadvantage of intermittency of electricity supply, making them difficult to merge with the electricity grid. [3] Growth of the renewable energy sector, therefore, requires efficient and eco-friendly energy conversion and storage (ECS) technologies, motivating aggressive technology development on many different fronts. Current advanced ECS systems include solar cells, [4] fuel cells, [5] photo/electrochemical water splitting systems, [6] secondary batteries (lithium (Li)-ion, [7] Li-sulfur batteries, [8] etc.), and supercapacitors. [9] Among these technologies, metalair batteries are attracting increasing attention due to their low cost and extremely high energy density. [10] A zinc-air battery (ZAB) has a theoretical specific energy density of 1086 Wh kg −1 , which is about 2.5 times higher than that of the Li-ion batteries now in widespread use. [11] Among the different metal-air batteries (metal = Zn, Li, Al, etc.) currently under development, ZABs are widely considered the most practical since Zn is earth abundant, they have a long and stable discharge, and use an aqueous electrolyte (typically 6 m KOH), which makes them safe to use. [12] Small primary ZABs are already used in a number of consumer devices such as hearing aids, while large ZABs with capacities up to 2000 Ah per cell are used to power navigational lighting. [13] Rechargeable or secondary ZABs are now being actively pursued by many research groups. The key bottleneck in the development of rechargeable ZABs is the need to discover a catalyst (or combination of catalysts) capable of efficiently driving the oxygen reduction reaction (ORR) during battery discharge and the oxygen evolution reaction (OER) during battery recharge. [14] Noble metal-based electrocatalysts are the current benchmark for ORR (using Pt/C) and OER (using IrO 2 /C or RuO 2 /C), though the scarcity and high cost of these metals prevent their use in large-scale applications. [11b,15] Accordingly, low cost and efficient catalysts must be designed for these reactions, with current research in the field focused on 1) reducing the amount of precious metal usage to the bare minimum or 2) completing

Dual‐Sites Coordination Engineering of Single Atom Catalysts for Flexible Metal–Air Batteries

“…Until recently, lots of strategies have been proposed to design the single atom catalysts and explore their applications in electrocatalysis. [ 24–26 ] Among them, single metal‐nitrogen structures are the most representative category in this community. [ 27,28 ] The metal‐substrate interaction in the single atom catalyst helps to promote the electron transfer between the metal atoms and the support, and regulate the electronic structure of the metal atoms, both of which are beneficial to the application of electrocatalysis.…”

Ionic-liquid-assisted synthesis of metal single-atom catalysts for benzene oxidation to phenol

“…Various methods have been developed to fabricate SACs, and they can be roughly categorized as "bottom-up" and "top-down" routes based on the starting precursors [7][8]. Nevertheless, abundant coordination heteroatoms or defects are required to stabilize single metal atoms during the preparation processes [9][10][11]. Heteroatoms with lone pairs of electrons, particularly, N, O, P, and S have strong coordination ability to anchor metal single atoms and provide SACs with unique electronic structures [12][13][14][15][16][17][18].…”

Single‐Atom Catalysts: A Sustainable Pathway for the Advanced Catalytic Applications

“…Large-scale electrical energy storage using rechargeable batteries works toward the current goal to shift fossil fuels to electric energy by deploying renewable sources, batteries are the way to store electric energy and can be used on-demand. [257] Many variants of batteries are produced such as Li-S, Na-S, or metal-air. [253,[258][259][260] Metal-air batteries (MABs) hold high energy density and a potential candidate for the future energy supplier of the next generation.…”

“…[266][267][268] In recent years, increasing interest in higher energy density, cheaper, and safer battery technology has stimulated tremendous research efforts toward the development of improved rechargeable Zn-air batteries (ZAB). [257] ZAB is one of the promising sustainable and green candidates using abundant and inexpensive resources with a decent energy density, and high reduction potential. [269] Number of decent efforts has been invested in for increasing the active sites, accessibility, and selectivity for electrocatalytic materials are effective for improving air electrode performance.…”