Realization Of Low-Cost Energy Storage And Conversion Technology: A Promising Air Electrode For Zn Air Battery

As a promising post-lithium-ion battery technology, rechargeable Zn air batteries have attracted intense attention due to their high theoretical energy and power density. However, the slow kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the air electrode has been the technical challenge for the practical application of Zn air battery. As such, the development of bifunctional electrocatalysts that can efficiently catalyze both ORR and OER is of prime importance. [1]

The state-of-art bifunctional electrocatalysts for ORR and OER in Zn air battery are noble-metal based materials, such as the mixture of platinum and Ruthenium oxide or the mixture of platinum and Iridium oxide. However, the commercialization of Zn air battery is greatly hampered by two fundamental factors. The first one is the high cost, scarcity of the noble metal, and the second one is the poor stability of the electrocatalysts in cyclic charging/discharging environment. Therefore, it is highly desirable but challenging to develop noble-metal-free catalysts for ORR and OER with high catalytic activity and good durability.

Researchers in Canada have developed a cost-effective, high-performance electrode material based on transition metal oxide with the perovskite structure for the efficient energy storage and conversion in Zn Air batteries. 

Researchers have shown that a perovskite oxide could be easily evolved into a hybrid catalyst through the facile surface chemistry approach. A small amount of carbon skin along with the iron carbide nanoparticles led to the remarkably enhanced electronic conductivity, heterogeneous exchange rate as well as the durability in oxygen electrocatalysis. As-obtained perovskite-based hybrid catalyst exemplified in their study is a stable, efficient, and tunable bifunctional catalyst for ORR and OER to substitute for the noble metals in Zn air battery.

The derived perovskite oxide is a good support material thanks to its reasonable reactivity and chemical stability. Iron carbide has a unique electronic structure, and therefore, can achieve superior catalytic activity. The application of iron carbide combined with perovskites is expected to modify the structural and electronic properties of the catalyst, thereby beneficial for the high performance.

Finally, the in situ formed carbon could (1) ensure strongly correlated interfaces, which helps extend the surface utilization and eliminate conductivity limitations of perovskite, (2) encapsulate iron carbide nanoparticles, enabling sufficient durability of iron carbide in the battery, and (3) catalyze reaction as demonstrated by many researchers.

As such, the significance of their study is two-fold: First of all, it presents an efficient, affordable, tunable and robust catalyst for Zn air battery; secondly, this unique route indeed shows the potential in designing well-defined and high-quality catalysts for energy storage and conversion devices.

While there’s still more work to be done, the new research findings could help researchers design Zn air battery systems that use these types of novel materials. Next, the research team is turning its focus to stabilizing the battery in order to prevent its swift degradation.

These findings are described in the article entitled A facile surface chemistry approach to bifunctional excellence for perovskite electrocatalysis, recently published in the journal Nano Energy. [2] This work was conducted by Dr. Bin Hua, Dr. Meng Li and Dr. Jing-Li Luo (University of Alberta, Canada).

References:

1. Bin Hua, Meng Li, Ya-Qian Zhang, Yi-Fei Sun, Jing-Li Luo, All-In-One Perovskite Catalyst: Smart Controls of Architecture and Composition toward Enhanced Oxygen/ Hydrogen Evolution Reactions, Adv. Energy Mater., 2017, 7, 1700666.
2. Bin Hua, Meng Li, Jing-Li Luo, A facile surface chemistry approach to bifunctional excellence for perovskite electrocatalysis, Nano Energy, 2018, 49, 117.