Highly stable bifunctional catalyst for Zn-Air batteries: The effect of a nitrated carbon support on Co_3O_4 activity

摘要

The use of Co3O4 as electrocatalyst in Zn-air batteries has been extensively studied. However, electrical rechargeability has only been achieved by combining metal oxides with precious metals or using a second electrode/electrolyte to promote the oxygen evolution reaction. In this work, we report efficient catalytic activity of Co3O4 for both, the oxygen reduction and oxygen evolution reaction by fusing Co3O4 particles to a nitrated carbon support. The functionalized carbon matrix improves not only the carbon wettability, but also provides acidic sites and carbon-containing functional groups. This synergistic configuration enhances the reaction kinetics especially for the oxygen evolution reaction. The electrochemical characterization demonstrated lower overpotential and higher stability over 160 cycles for the Co3O4 catalyst attached to the nitrated carbon matrix compared to the pristine carbon matrix. Electrochemical impedance spectroscopy demonstrated 21 times lower degradation for the functionalized air-cathode at 2 mA cm(-2), 12.4 times lower degradation at 5 mA cm(-2), and 1.15 times lower degradation at 10 mA cm(-2). Although further work is required, the low-cost process and the electrochemical performance of this catalyst represent considerable progress towards the development of rechargeable and flexible Zn-air batteries.