Towards the scale up of a pressurized-jet microfluidic flow-through reactor for cost-effective electro-generation of H2O2

The performance of a novel pressurized-jet microfluidic flow-through electrolyzer for the production of aqueous solution of H2O2 is assessed in this work. The reactor design is based on three aspects i) minimizing ohmic drops, by reducing the interelectrode gap to 150 μm and the use of a Duocel® aluminum foam as cathodic support; ii) maximizing mass transport, due to the use of three-dimensional electrodes fed in flow-through and iii) optimizing the aeration system coupling a pressurized circuit and a jet aerator. Results show that H2O2 can be produced with an instantaneous current efficiency of 100% up to 20 mA cm−3 and a corresponding production rate of 13.1 mg H2O2 h−1 cm−3 in a cathode of 16.5 cm3. Low ohmic resistances were measured even in low-conductive electrolytes, as for example 6 Ω in 0.0035 M Na2SO4 (0.7 mS cm−1). The electrical energy consumption of 3.65 kWh kg H2O2−1 at 10 mA cm−3 in 0.05 M Na2SO4 is the lowest reported so far in neutral-acid medium, confirming the cost-effectiveness of the system. A preliminary scale-up by increasing the cathode volume three times (up to 49.5 cm3) allowed the production rate to be multiplied by the same factor and confirms that the system is scalable. Theoretical calculations suggest that the cathode could be expanded up to 3600 cm3 (1 m thickness) under those aeration conditions (6 bar and 160 dm3 h−1 recirculation flow)