Employing a Zn-air/Photo-Electrochemical Cell for In Situ Generation of H2O2 for Onsite Control of Pollutants.

Industrial production of hydrogen peroxide (H₂O₂) is energy-intensive and generates unwanted byproducts. Herein, an alternative production strategies of H₂O₂ are demonstrated in a Zn-air and a photoelectrochemical cell. Employing an optimally produced reduced graphene oxide (rGO) electrocatalyst@air-cathode, an impressive power density of 320 Wm_geo ^-2 (geo = geometric area) is achieved along with a high H₂O₂ production rate of 3.17 mol m_geo ^-2h^-1 (operating potential = 0.8 V). Systematic investigations reveal the critical role of specific functional groups (viz. C─O─C, chemisorbed O₂, C≐C) to be responsible for enhancing the yield of H₂O₂. The in situ generated superoxide (O₂˙) and hydroxyl radicals (˙OH) act as oxidants to efficiently degrade onsite, a model textile dye pollutant (viz. rhodamine B) inside the Zn-air cell. Using the identical rGO as the photoelectrode in an H-type cell, the H₂O₂ production is remarkably enhanced under visible light illumination. Simultaneously, the onsite pollutant degradation occurs five times faster than the Zn-air cell (at the same operating potential = 0.8 V). This work opens a new paradigm for electrosynthesis, wherein an underlying redox can be utilized to synthesize industrial chemicals for onsite control of environmental pollution sustainably.