Letter pubs.acs.org/NanoLett
M13 Virus-Directed Synthesis of Nanostructured Metal Oxides for Lithium−Oxygen Batteries Dahyun Oh,†,‡ Jifa Qi,†,‡ Binghong Han,†,§ Geran Zhang,†,‡ Thomas J. Carney,†,§ Jacqueline Ohmura,‡,∥ Yong Zhang,⊥ Yang Shao-Horn,*,†,§,# and Angela M. Belcher*,†,‡,∥ †
Department of Materials Science and Engineering, ‡The David H. Koch Institute for Integrative Cancer Research, §Electrochemical Energy Laboratory, ∥Department of Biological Engineering, ⊥Center for Materials Science and Engineering, and #Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States S Supporting Information *
ABSTRACT: Transition metal oxides are promising electrocatalysts for both water oxidations and metal−air batteries. Here, we report the virus-mediated synthesis of cobalt manganese oxide nanowires (NWs) to fabricate high capacity Li−O2 battery electrodes. Furthermore, we hybridized Ni nanoparticles (NPs) on bio Co3O4 NWs to improve the round trip efficiency as well as the cycle life of Li−O2 batteries. This biomolecular directed synthesis method is expected to provide a selection platform for future energy storage electrocatalysts. KEYWORDS: Biotemplation, Li-oxygen battery, M13 virus, nanowire synthesis, cobalt manganese oxides, composite structure
T
designate them as MCO) have presented considerable catalytic activities for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) in alkaline solutions.12,13 Furthermore, they were also studied in previous reports as costeffective electrocatalysts for Zn−air10 and Li−air batteries, but with varied geometries,10,14 or with carbonate-based electrolytes,15 which decompose during Li−air battery operations.16 Here, we first report the biomolecule-directed synthesis of MCO to investigate their functionalities as Li−O2 battery cathodes with relatively stable17 ether-based electrolytes. While the conventional synthetic methods generated random sizes of particles,15,18 plates,19 and spheres20 of MCO, the M13 virus enabled us to form homogeneously distributed, high-aspect ratio MCO NWs (∼50 nm of diameter and ∼1 μm of length). Thus, we could observe the correlation between the Li−O2 battery performance and the chemical composition of bio MCO NWs while confining the geometry of cathode materials in a similar scale. Among many different types of organic templates for nanomaterial synthesis,21−23 M13 viruses have unique properties, including a high aspect ratio of geometry (∼880 nm long and ∼6 nm in diameter, Figure 1A), genetic tunability of surface protein, and easy replicability. Their viral capsids are composed of 2700 copies of helically arranged major coat proteins, p8, and 5−7 copies of each of p3, p6, p9, and p7, located at either ends of M13 virus. These proteins can be genetically modified to display peptide sequences (
