Amorphous Bimetallic Oxide-Graphene Hybrids as Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Battery

Yuan Chen

The University of Sydney

Abstract: Metal oxides of earth-abundant elements are promising electrocatalysts to overcome the sluggish oxygen evolution and oxygen reduction reaction (OER/ORR) in Zn-air batteries. However, their catalytic activity is hard to be precisely controlled. Here, we describe a general three-stage synthesis strategy to produce a family of hybrid materials comprising amorphous bimetallic oxide nanoparticles anchored on N–doped reduced graphene oxide with simultaneous control of nanoparticle elemental composition, size, and crystallinity. Amorphous Fe0.5Co0.5Ox was obtained from Prussian blue analogue nanocrystals, showing excellent OER activity with a Tafel slope of 30.1 mV dec–1 and an overpotential of 257 mV for 10 mA/cm–2 and superior ORR activity with a large limiting current density of –5.25 mA cm–2 at 0.6 V. Zn-air battery delivers a specific capacity of 756 mAh gZn–1 (corresponding to an energy density of 904 Wh kgZn–1), a peak power density of 86 mW cm-2 and can be cycled over 120 hours at 10 mA cm-2. Other two amorphous bimetallic, Ni0.4Fe0.6Ox and Ni0.33Co0.67Ox, were also produced to demonstrate the general applicability of this method for synthesizing binary metal oxides with controllable structures as electrocatalysts for energy conversions.

Biography: Professor Yuan Chen received Bachelor's and Master's degrees from Tsinghua University in China, and a PhD from Yale University in the United States. He was at Nanyang Technological University in Singapore from 2005 to 2015. He joined the University of Sydney in 2015. His research focuses on developing scalable processes to synthesize carbon nanomaterials with well-defined atomic structures, assemble nanoscale carbon nanomaterials into functional macroscale structures, and use these novel materials for sustainable energy and environmental applications. In particular, his research team works on applications related to energy and water, such as high energy density supercapacitors, fiber supercapacitors for smart textiles, Zn-air batteries, electrocatalysts for hydrogen evolution, oxygen reduction, oxygen evolution reactions, carbon-based membranes, and antibacterial coatings. He received the Australian Research Council Future Fellowship (Level 3) in 2016, an Excellence in Review Award from Carbon in 2015, a Young Scientist Award from the Singapore National Academy of Science in 2011, a Tan Chin Tuan Exchange Fellowship in Engineering in 2010, and JSPS exchange award in 2009. He is currently serving as an editor for Carbon (impact factor 6.337) and Nanomaterials (impact factor 3.553). He also serves as Chair for Australian Carbon Society and Asian Association of Carbon Groups since August 2017.