Earth-abundant metal-free carbon-based electrocatalysts for Zn-air batteries to power electrochemical generation of H2O2 for in-situ wastewater treatment

The overuse of fossil fuel has caused a serious energy crisis and environmental pollution. In this study, we rationally devised an integrated system, in which novel earth-abundant metal-free carbon-based electrocatalysts were used to catalyze oxygen reduction reaction (ORR) in Zn-air batteries for renewable energy storage as a power source for electrochemical generation of H2O2 as an oxidant for in-situ degradation of pollutants in wastewater. It was noted that the newly-developed ordered mesoporous carbon (OMC) and N-doped OMC (NOMC) exhibited high selectivity for 2e(-) ORR to produce H2O2 and high selectivity for 4e(-) ORR at the cathode of Zn-air batteries, respectively. The OMC electrode showed a H2O2 yield as high as 366.9 mg/L in 2 h at 0.5 V, leading to a high current efficiency similar to 73.6%, The subsequent use of thus-produced H2O2 for Rhodamine B (RhB) candidate pollutant degradation exhibited an 90% removal efficiency in 2 h, showing a great promise for practical wastewater treatment. This work represents a breakthrough in the development of a new concept and novel integrated systems to address the current energy and environmental changes.