Biologically synthesized TiO2 nanoparticles and their application as lithium-air battery cathodes

Abstract

Electrocatalysts represent a sustainable solution for lithium-air batteries by eliminating side reactions. Herein, TiO2 nanoparticles were biosynthesized via the green method and investigated as air cathodes for lithium-air batteries. TiO2 nanoparticles were also synthesized via the facile sol-gel method to compare the efficiency of this green method. The flower extract of Matricaria chamomilla was utilized to biosynthesize the TiO2 nanoparticles. The particle size of the biosynthesized TiO2 nanoparticles was further controlled by manipulating the pH of the solution. In this way, the influence of pH on the nanoparticle's properties could be evaluated. The phase structures, surface morphology, and elemental composition of the synthesized TiO2 nanoparticles were characterized as well. Additionally, the TiO2 cathodes were prepared on nickel foam, and their electrochemical performances were evaluated via an ECC-Air test cell using cyclic voltammetry, electrochemical impedance measurements, and galvanostatic charge-discharge tests. Consequently, the Bio-TiO2 air cathode showed a full discharge capacity of 2000 mAh g(-1) and a specific capacity of 500 mAh g(-1Y) for 30 stable cycles.