Electronic Tuning of Core–Shell CoNi Nanoalloy/N-Doped Few-Layer Graphene for Efficient Oxygen Electrocatalysis in Rechargeable Zinc–Air Batteries

Abstract

The discovery of highly efficient, durable, and affordable bifunctional ORR/OER electrocatalysts is of great significance for the commercialization of rechargeable metal–air batteries. Herein, we synthesized uniformly sized CoNi alloy nanoparticles encapsulated with N-doped few-layer graphene (N-FLG) sheets via pyrolysis of a CoNi dual metal–organic framework precursor. The developed CoNi/N-FLG catalyst exhibited excellent oxygen reduction activity (comparable to a commercial 20 wt % Pt/C catalyst) and outstanding oxygen evolution activity (superior to a commercial 20 wt % IrO2/C catalyst), thus enabling efficient bifunctional oxygen electrocatalysis and stability when applied in prototype rechargeable zinc–air batteries. The remarkable electrochemical properties of CoNi/N-FLG originate from its unique core–shell structure and favorable electron penetration effects, thereby optimizing the adsorption/desorption strengths of intermediates formed during the oxygen reduction and oxygen evolution reactions.

Metal–organic framework-derived advanced oxygen electrocatalysts as air-cathodes for Zn–air batteries: recent trends and future perspectives

“…12c). 123 The unique core–shell structure with well-defined nanoscale components and favorable migration of the CoNi alloy valence electrons to the N-doped graphene shell mainly accounted for the bifunctional electrocatalytic activity and stability. This facile electron penetration effect largely helped to optimize the adsorption/desorption strengths of the intermediates formed during the ORR and OER, which was further validated by the Gibbs free energy profiles (Fig.…”

“…(c) Schematic for the synthesis of CoNi/N-FLG and Gibbs free energy diagrams for (d) ORR and (e) OER. Reproduced with permission 123. Copyright 2021, 2022, the American Chemical Society.…”

Copper-Doped Cobalt Oxychloride for Efficient Oxygen Evolution Reactions in an Alkaline Medium

“…[1][2][3]6 Hence, fabricating an efficient OER electrocatalyst is the dire need of the hour. 7,8 It is well recognized that an active hydroxide, more preferably an oxyhydroxide layer, is formed on the surface of the electrocatalyst in an alkaline environment. 9−15 Although active layers obtained from high valence metal oxy(hydroxide) are believed to be the actual active species, this cannot explain why numerous catalysts exhibit different activities with respect to oxidation states.…”

“…Electrochemical oxygen evolution reaction (OER) is a key step in the energy storage and conversion process such as carbon dioxide reduction (CO 2 RR), rechargeable metal–air batteries, water electrolysis, and in fuel cells. − The electrochemical oxygen evolution reaction (OER) is a complex four-electron proton transfer process, which owes to its slower kinetics due to the bond formation of oxygen to oxygen. − , Hence, fabricating an efficient OER electrocatalyst is the dire need of the hour. , It is well recognized that an active hydroxide, more preferably an oxyhydroxide layer, is formed on the surface of the electrocatalyst in an alkaline environment. − Although active layers obtained from high valence metal oxy­(hydroxide) are believed to be the actual active species, this cannot explain why numerous catalysts exhibit different activities with respect to oxidation states. Additionally, understanding the relationship between catalytic performance and active elements is highly dependent on identifying the operando-structure at atomic-level precision. − Thus, it is essential to use very effective OER catalysts with a well-defined structure after reconstruction and to understand the relationship between structure–activity based on accurate recognition of reconstruction-derived components.…”

l-Alanine-Assisted Synthesis of a Hierarchically Porous Co@N–C/N-Ketjenblack Carbon Catalyst for Oxygen Reduction in Zn–Air Batteries

“…Zinc–air batteries (ZABs) are presently attracting a lot of interest as a power due to their high theoretical specific energy capacity (1086 W h kg –1 ), inherent safeness, non-toxicity, and low cost. , However, the practical energy capacity of ZABs is presently much lower than the theoretical value and one of the main reasons for it is the sluggish kinetics of four-electron-transfer oxygen reduction reaction (ORR) that occurs on the air cathode during battery discharge. , Currently, Pt-based catalysts are typically used in ZABs to drive the ORR. However, the high cost, scarcity, and poor stability of Pt-based catalysts represent obstacles to the widespread application of ZABs. − Hence, the discovery of highly efficient non-precious metal-based electrocatalysts for ORR is an imperative. − …”