Scientists from SASTRA Deemed University, Thanjavur, have developed a breakthrough nanofluid electrolyte technology for electrically rechargeable zinc-air batteries (ZABs), supported by the Department of Science and Technology under the Nano and Advanced Materials Division. The technology addresses two major challenges that have hindered zinc-air batteries: unwanted hydrogen gas evolution at the zinc anode that wastes charge and corrodes the metal, and sluggish oxygen reactions at the air-cathode that typically require expensive platinum or ruthenium catalysts.
The innovation involves dispersing small amounts of inexpensive silica and zinc oxide nanoparticles into the standard electrolyte, creating a nanofluid electrolyte that suppresses hydrogen reaction while simultaneously inhibiting corrosion and enhancing oxygen reaction performance at the cathode. This solution solves both electrode problems with one low-cost intervention, with the electrolyte demonstrating stability over three months and being directly applicable to the zinc-air battery industry.
The technology is protected by granted Indian patent IN570691 and is ready for commercial usage. The research team, led by Dr. S. Devaraj, also developed earth-abundant bifunctional catalysts to drive both oxygen reduction (ORR) and oxygen evolution (OER) efficiently. Their research identified α-MnO₂ as the top catalyst performer due to its open tunnel-like architecture, with strategic copper doping pushing performance beyond commercial benchmarks at a remarkably low dopant loading of just 2 wt%, outperforming both platinum- and ruthenium-based standards.
Additionally, the team explored waste-derived materials, recovering spent activated carbon from exhausted household water filters and hydrothermally converting it into MnO₂/C nanocomposites for both efficient bifunctional electrocatalysts and high-performing supercapacitor electrodes (patent application No. 202441032753). They also chemically upcycled post-pandemic surgical face masks into activated carbon with a record-high surface area that rivals platinum in oxygen reduction activity.
The developed approaches have prospects beyond zinc-air battery technology, as the waste-derived carbon can be tuned for multiple applications and the upcycling approach is adaptable to virtually any waste carbon source. Similarly, the nanofluid electrolyte concept can potentially extend to other aqueous battery systems, offering a generalizable strategy for safer, cheaper, next-generation green batteries with applications in grid-scale storage and supporting electric mobility in India.