Unveiling an In Situ H₂O₂ Production: Rechargeable Zinc-H₂O₂ Battery Powering 26 LEDs

Looking toward ever-growing energy demand, the advancement in energy storage devices and carrying out electrocatalytic reactions in an efficient way is the need of the hour. Herein, we have employed the two birds-one stone approach, viz. fusing energy conversion and storing system enabling 2e^- oxygen reduction reaction (ORR) to value-added hydrogen peroxide (H₂O₂) product and its utilization in the energy storage devices using MnWO₄ catalyst, without any external H₂O₂ source. The designed catalyst exhibited a remarkable H₂O₂ production of 98% @ 0.37 V versus RHE. The real-time H₂O₂ production was monitored by in-situ electrochemical Raman and in-situ infrared spectroscopic measurements. The pivotal influence of electrolyte composition, viz. local pH and the formation of carbonate species on H₂O₂ production was meticulously examined through micro-electrochemical studies using gold (Au) microelectrodes. Further, we have explored an aqueous rechargeable Zn-H₂O₂ battery utilizing MnWO₄ as bifunctional electrocatalyst for sustainable H₂O₂ production simultaneously producing the electricity. The Zn-H₂O₂ battery exhibited a remarkable cycle life of 136 h and an practical energy efficiency of 43%. The galvanostatic charge-discharge measurement of Zn-H₂O₂ battery attained a capacity of 25 mAh cm^-2 at 3 mA cm^-2. The battery also demonstrated ≥90% cycle efficiency. Interestingly, the designed Zn-H₂O₂ battery (two connected in series) exhibited a stable open circuit voltage (OCV) with a promising power density of 10.5 mW cm^-2. As a proof of concept, we have demonstrated Zn-H₂O₂ batteries by powering 26 blue LEDs for more than 180 h (7 days) without fading in the illumination of LEDs.