Tandem-Parallel Electrochemical Cells to Produce Hydrogen Peroxide at Reduced Energy Consumption

Large-scale industrialization of oxygen electroreduction requires producing hydrogen peroxide (H₂O₂) at large yield rates (current density >1 A cm^-2, Faradic efficiency >95%). Under such vigorous reaction conditions, however, serious electric energy consumption (EEC) has been caused. According to the formula ($\mathrm{EEC}=\frac{Y\times 1000\times R\times F^2}{{17}^2\times {\mathrm{FE}}^2}$), a linear relationship can be identified between H₂O₂ yield rates (Y) and EEC, and therefore, achieving high yield rates (Y) while reducing EEC is very challenging in common electrochemical systems. In this work, we have designed a tandem-parallel oxygen electroreduction system composed of two oxygen electroreduction units. The tandem unit can effectively improve the Faradaic efficiency (FE) while the parallel section reduces total internal resistance (R). Consequently, the overall system can achieve a high H₂O₂ yield rate (592 mg h^-1) with the lowest EEC (2.41 kWh kg^-1) ever reported to the best of our knowledge. Further, the tandem-parallel system has shown promising stability by working for more than 10 cycles or 24 h. Besides oxygen electroreduction, other applications have been also demonstrated for the tandem-parallel system that can generate H₂O₂ for in situ degradation of rhodamine B pollutant.