Electrocatalytic Mechanisms in Zinc-Air Batteries

Zinc-air batteries operate by oxidising zinc at the anode and reducing oxygen at the air cathode to generate electricity. Central to their performance are the electrocatalytic mechanisms that govern the oxygen reduction reaction (ORR) during discharge and the oxygen evolution reaction (OER) during charge. In the ORR pathway, molecular oxygen is adsorbed onto active sites, accepts electrons and protons, and is either directly reduced to hydroxide via a four-electron pathway or partially reduced to peroxide intermediates in a two-electron pathway. Efficient catalysts promote the four-electron route, suppressing peroxide formation and enhancing energy efficiency. During charging, the OER reverses this process, liberating oxygen from hydroxide and returning the cell to its discharged state. Bifunctional electrocatalysts capable of mediating both ORR and OER thus lie at the heart of rechargeable zinc-air systems. Advances in nanostructured carbon supports, transition-metal–nitrogen coordination sites and metal-organic frameworks have refined the geometry, electronic structure and porosity of air electrodes, accelerating reaction kinetics and improving durability. Optimising local pH, ionic conductivity of electrolytes and gas diffusion layers further tunes reaction zones and limits carbonate formation. Together, these developments aim to deliver high energy density, long cycle life and low cost for applications ranging from grid storage to portable and wearable electronics.

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Electrocatalytic Mechanisms in Zinc-Air Batteries publication trend

The graph below shows the total number of articles in electrocatalytic mechanisms in zinc-air batteries across all publications each year (not limited to Nature Index journals).

Technical terms

Oxygen reduction reaction (ORR): The electrochemical process in which O₂ gains electrons and protons to form hydroxide ions, determining discharge efficiency.

Oxygen evolution reaction (OER): The reverse electrocatalytic process in which hydroxide ions release oxygen and protons, essential for charging rechargeable cells.

Bifunctional electrocatalyst: A catalyst capable of efficiently mediating both ORR and OER, reducing overpotentials in both discharge and charge modes.

Peroxide intermediate: A partially reduced oxygen species (O₂²⁻) formed during two-electron ORR pathways that can degrade performance if not fully converted.

MBene: A family of two-dimensional metal boride or carbide materials with tunable vacancies and high surface reactivity, applied here for near-neutral zinc-air catalysis.

References

1. Carbon-Based Electrodes for Advanced Zinc-Air Batteries: Oxygen-Catalytic Site Regulation and Nanostructure Design. Electrochemical Energy Reviews (2023).
2. A Review of Rechargeable Zinc–Air Batteries: Recent Progress and Future Perspectives. Nano-Micro Letters (2024).
3. Atomically Dispersed Transition Metal-Nitrogen-Carbon Bifunctional Oxygen Electrocatalysts for Zinc-Air Batteries: Recent Advances and Future Perspectives. Nano-Micro Letters (2021).
4. MBene promoted Zn peroxide chemistry in rechargeable near-neutral Zn–air batteries. Energy & Environmental Science (2023).