Design of a sectionalized MnO2-Co3O4 electrode via selective electrodeposition of metal ions in hydrogel for enhanced electrocatalytic activity in metal-air batteries

Tailored designing of highly active electrocatalysts plays a key role in determining the overall electrochemical performance of metal-air batteries for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We report herein a facile agarose gel-mediated strategy for the selective electrodeposition of MnO2 and Co3O4 onto 3D porous nickel foam, in an attempt to produce a sectionalized MnO2-Co3O4 electrode with low physical interference on catalytic function. The as-prepared agarose hydrogel with metal precursor ions allows the electrochemical deposition only onto the contact area between the gel and the substrate. The resulting electrodes are completely sectionalized by two different catalyst (MnO2 and Co3O4) coating layers within the 3D porous nickel foam. This novel structure enhances both the ORR/OER catalytic activities compared to those of bare metal oxide catalyst electrodes and even after 400 h of operation (equivalent to 100 cycles), the sectionalized MnO2-Co3O4 electrode shows excellent cycling performance and long-term stability in rechargeable Zn-air batteries. As such, this novel sectionalized electrode configuration has potential for wide applications in the fabrication of other electrode structures employing various metal oxides.