Bi-functional Catalysts & Electrode Structures for Electrochemically Rechargeable Metal-Air Batteries

Electrochemically Rechargeable Metal-Air Batteries are a promising future energy storage technology, due to their high theoretical specific energy, i.e. 1350 or 11140 Wh kg-1 (excluding oxygen) for Zinc-air or Li-air battery, respectively, compared with 100-265 Wh kg-1 for current Li-ion batteries. Aqueous metal-air batteries (i.e. Zn-air) are of particular interest for the large scale grid storage as this is potentially one of the low-cost solutions. Major challenges of Zn-air batteries, however, lie in the following: 1) rechargeability; 2) round-trip efficiency and 3) power density, which ultimately determine the cost-effectiveness & life-time of the developed system.
In order to achieve cost-effective and highly durable metal-air batteries, the first-priority is to develop efficient oxygen reduction / evolution (ORR / OER) bi-functional catalysts. The existing commercial benchmark, i.e. platinum or iridium oxide supported on carbon (Pt/C or IrO2/C), suffers from their scarcity and poor durability. In fact, neither is 'truly' bi-functional. Preliminary work in Prof. Guo's group has shown that a series of non-precious metal / porous carbon composites and even metal-free (i.e. heteroatom-doped graphene) catalysts surpass the ORR/OER activities of Pt/C and IrO2/C, respectively. Such mechanistic study will be characterized by our state-of-the-art electrochemical atomic force microscopy (EC-AFM) technique, which allows for the in-situ measurement of morphology / chemical environment change on the electrode surface during charging / discharging, which facilitates the probe of active sites for catalytic oxygen reduction / evolution and the study on battery degradation mechanism. In addition, we will aim to develop in situ methods to use advanced characterization methods involving Synchrotron radiation techniques to determine the structure of the materials.